Adding upstream version 252.22.upstream/252.22upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1601 insertions, 0 deletions

diff --git a/src/coredump/coredump.c b/src/coredump/coredump.c
new file mode 100644
index 0000000..d5ea5ea
--- /dev/null
+++ b/src/coredump/coredump.c
@@ -0,0 +1,1601 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <errno.h>
+#include <stdio.h>
+#include <sys/prctl.h>
+#include <sys/statvfs.h>
+#include <sys/auxv.h>
+#include <sys/xattr.h>
+#include <unistd.h>
+
+#include "sd-daemon.h"
+#include "sd-journal.h"
+#include "sd-login.h"
+#include "sd-messages.h"
+
+#include "acl-util.h"
+#include "alloc-util.h"
+#include "bus-error.h"
+#include "capability-util.h"
+#include "cgroup-util.h"
+#include "compress.h"
+#include "conf-parser.h"
+#include "copy.h"
+#include "coredump-vacuum.h"
+#include "dirent-util.h"
+#include "elf-util.h"
+#include "escape.h"
+#include "fd-util.h"
+#include "fileio.h"
+#include "fs-util.h"
+#include "io-util.h"
+#include "journal-importer.h"
+#include "journal-send.h"
+#include "log.h"
+#include "macro.h"
+#include "main-func.h"
+#include "memory-util.h"
+#include "mkdir-label.h"
+#include "parse-util.h"
+#include "process-util.h"
+#include "signal-util.h"
+#include "socket-util.h"
+#include "special.h"
+#include "stat-util.h"
+#include "string-table.h"
+#include "string-util.h"
+#include "strv.h"
+#include "sync-util.h"
+#include "tmpfile-util.h"
+#include "uid-alloc-range.h"
+#include "unaligned.h"
+#include "user-util.h"
+
+/* The maximum size up to which we process coredumps. We use 1G on 32bit systems, and 32G on 64bit systems */
+#if __SIZEOF_POINTER__ == 4
+#define PROCESS_SIZE_MAX ((uint64_t) (1LLU*1024LLU*1024LLU*1024LLU))
+#elif __SIZEOF_POINTER__ == 8
+#define PROCESS_SIZE_MAX ((uint64_t) (32LLU*1024LLU*1024LLU*1024LLU))
+#else
+#error "Unexpected pointer size"
+#endif
+
+/* The maximum size up to which we leave the coredump around on disk */
+#define EXTERNAL_SIZE_MAX PROCESS_SIZE_MAX
+
+/* The maximum size up to which we store the coredump in the journal */
+#ifndef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
+#define JOURNAL_SIZE_MAX ((size_t) (767LU*1024LU*1024LU))
+#else
+/* oss-fuzz limits memory usage. */
+#define JOURNAL_SIZE_MAX ((size_t) (10LU*1024LU*1024LU))
+#endif
+
+/* When checking for available memory and setting lower limits, don't
+ * go below 4MB for writing core files to storage. */
+#define PROCESS_SIZE_MIN (4U*1024U*1024U)
+
+/* Make sure to not make this larger than the maximum journal entry
+ * size. See DATA_SIZE_MAX in journal-importer.h. */
+assert_cc(JOURNAL_SIZE_MAX <= DATA_SIZE_MAX);
+
+enum {
+        /* We use these as array indexes for our process metadata cache.
+         *
+         * The first indices of the cache stores the same metadata as the ones passed by
+         * the kernel via argv[], ie the strings array passed by the kernel according to
+         * our pattern defined in /proc/sys/kernel/core_pattern (see man:core(5)). */
+
+        META_ARGV_PID,          /* %P: as seen in the initial pid namespace */
+        META_ARGV_UID,          /* %u: as seen in the initial user namespace */
+        META_ARGV_GID,          /* %g: as seen in the initial user namespace */
+        META_ARGV_SIGNAL,       /* %s: number of signal causing dump */
+        META_ARGV_TIMESTAMP,    /* %t: time of dump, expressed as seconds since the Epoch (we expand this to µs granularity) */
+        META_ARGV_RLIMIT,       /* %c: core file size soft resource limit */
+        META_ARGV_HOSTNAME,     /* %h: hostname */
+        _META_ARGV_MAX,
+
+        /* The following indexes are cached for a couple of special fields we use (and
+         * thereby need to be retrieved quickly) for naming coredump files, and attaching
+         * xattrs. Unlike the previous ones they are retrieved from the runtime
+         * environment. */
+
+        META_COMM = _META_ARGV_MAX,
+        _META_MANDATORY_MAX,
+
+        /* The rest are similar to the previous ones except that we won't fail if one of
+         * them is missing. */
+
+        META_EXE = _META_MANDATORY_MAX,
+        META_UNIT,
+        META_PROC_AUXV,
+        _META_MAX
+};
+
+static const char * const meta_field_names[_META_MAX] = {
+        [META_ARGV_PID]       = "COREDUMP_PID=",
+        [META_ARGV_UID]       = "COREDUMP_UID=",
+        [META_ARGV_GID]       = "COREDUMP_GID=",
+        [META_ARGV_SIGNAL]    = "COREDUMP_SIGNAL=",
+        [META_ARGV_TIMESTAMP] = "COREDUMP_TIMESTAMP=",
+        [META_ARGV_RLIMIT]    = "COREDUMP_RLIMIT=",
+        [META_ARGV_HOSTNAME]  = "COREDUMP_HOSTNAME=",
+        [META_COMM]           = "COREDUMP_COMM=",
+        [META_EXE]            = "COREDUMP_EXE=",
+        [META_UNIT]           = "COREDUMP_UNIT=",
+        [META_PROC_AUXV]      = "COREDUMP_PROC_AUXV=",
+};
+
+typedef struct Context {
+        const char *meta[_META_MAX];
+        size_t meta_size[_META_MAX];
+        pid_t pid;
+        bool is_pid1;
+        bool is_journald;
+} Context;
+
+typedef enum CoredumpStorage {
+        COREDUMP_STORAGE_NONE,
+        COREDUMP_STORAGE_EXTERNAL,
+        COREDUMP_STORAGE_JOURNAL,
+        _COREDUMP_STORAGE_MAX,
+        _COREDUMP_STORAGE_INVALID = -EINVAL,
+} CoredumpStorage;
+
+static const char* const coredump_storage_table[_COREDUMP_STORAGE_MAX] = {
+        [COREDUMP_STORAGE_NONE]     = "none",
+        [COREDUMP_STORAGE_EXTERNAL] = "external",
+        [COREDUMP_STORAGE_JOURNAL]  = "journal",
+};
+
+DEFINE_PRIVATE_STRING_TABLE_LOOKUP(coredump_storage, CoredumpStorage);
+static DEFINE_CONFIG_PARSE_ENUM(config_parse_coredump_storage, coredump_storage, CoredumpStorage, "Failed to parse storage setting");
+
+static CoredumpStorage arg_storage = COREDUMP_STORAGE_EXTERNAL;
+static bool arg_compress = true;
+static uint64_t arg_process_size_max = PROCESS_SIZE_MAX;
+static uint64_t arg_external_size_max = EXTERNAL_SIZE_MAX;
+static uint64_t arg_journal_size_max = JOURNAL_SIZE_MAX;
+static uint64_t arg_keep_free = UINT64_MAX;
+static uint64_t arg_max_use = UINT64_MAX;
+
+static int parse_config(void) {
+        static const ConfigTableItem items[] = {
+                { "Coredump", "Storage",          config_parse_coredump_storage,     0, &arg_storage           },
+                { "Coredump", "Compress",         config_parse_bool,                 0, &arg_compress          },
+                { "Coredump", "ProcessSizeMax",   config_parse_iec_uint64,           0, &arg_process_size_max  },
+                { "Coredump", "ExternalSizeMax",  config_parse_iec_uint64_infinity,  0, &arg_external_size_max },
+                { "Coredump", "JournalSizeMax",   config_parse_iec_size,             0, &arg_journal_size_max  },
+                { "Coredump", "KeepFree",         config_parse_iec_uint64,           0, &arg_keep_free         },
+                { "Coredump", "MaxUse",           config_parse_iec_uint64,           0, &arg_max_use           },
+                {}
+        };
+
+        return config_parse_many_nulstr(
+                        PKGSYSCONFDIR "/coredump.conf",
+                        CONF_PATHS_NULSTR("systemd/coredump.conf.d"),
+                        "Coredump\0",
+                        config_item_table_lookup, items,
+                        CONFIG_PARSE_WARN,
+                        NULL,
+                        NULL);
+}
+
+static uint64_t storage_size_max(void) {
+        if (arg_storage == COREDUMP_STORAGE_EXTERNAL)
+                return arg_external_size_max;
+        if (arg_storage == COREDUMP_STORAGE_JOURNAL)
+                return arg_journal_size_max;
+        assert(arg_storage == COREDUMP_STORAGE_NONE);
+        return 0;
+}
+
+static int fix_acl(int fd, uid_t uid, bool allow_user) {
+        assert(fd >= 0);
+        assert(uid_is_valid(uid));
+
+#if HAVE_ACL
+        int r;
+
+        /* We don't allow users to read coredumps if the uid or capabilities were changed. */
+        if (!allow_user)
+                return 0;
+
+        if (uid_is_system(uid) || uid_is_dynamic(uid) || uid == UID_NOBODY)
+                return 0;
+
+        /* Make sure normal users can read (but not write or delete) their own coredumps */
+        r = fd_add_uid_acl_permission(fd, uid, ACL_READ);
+        if (r < 0)
+                return log_error_errno(r, "Failed to adjust ACL of the coredump: %m");
+#endif
+
+        return 0;
+}
+
+static int fix_xattr(int fd, const Context *context) {
+
+        static const char * const xattrs[_META_MAX] = {
+                [META_ARGV_PID]       = "user.coredump.pid",
+                [META_ARGV_UID]       = "user.coredump.uid",
+                [META_ARGV_GID]       = "user.coredump.gid",
+                [META_ARGV_SIGNAL]    = "user.coredump.signal",
+                [META_ARGV_TIMESTAMP] = "user.coredump.timestamp",
+                [META_ARGV_RLIMIT]    = "user.coredump.rlimit",
+                [META_ARGV_HOSTNAME]  = "user.coredump.hostname",
+                [META_COMM]           = "user.coredump.comm",
+                [META_EXE]            = "user.coredump.exe",
+        };
+
+        int r = 0;
+
+        assert(fd >= 0);
+
+        /* Attach some metadata to coredumps via extended
+         * attributes. Just because we can. */
+
+        for (unsigned i = 0; i < _META_MAX; i++) {
+                int k;
+
+                if (isempty(context->meta[i]) || !xattrs[i])
+                        continue;
+
+                k = fsetxattr(fd, xattrs[i], context->meta[i], strlen(context->meta[i]), XATTR_CREATE);
+                if (k < 0 && r == 0)
+                        r = -errno;
+        }
+
+        return r;
+}
+
+#define filename_escape(s) xescape((s), "./ ")
+
+static const char *coredump_tmpfile_name(const char *s) {
+        return s ? s : "(unnamed temporary file)";
+}
+
+static int fix_permissions(
+                int fd,
+                const char *filename,
+                const char *target,
+                const Context *context,
+                uid_t uid,
+                bool allow_user) {
+
+        int r;
+
+        assert(fd >= 0);
+        assert(target);
+        assert(context);
+
+        /* Ignore errors on these */
+        (void) fchmod(fd, 0640);
+        (void) fix_acl(fd, uid, allow_user);
+        (void) fix_xattr(fd, context);
+
+        r = fsync_full(fd);
+        if (r < 0)
+                return log_error_errno(r, "Failed to sync coredump %s: %m", coredump_tmpfile_name(filename));
+
+        r = link_tmpfile(fd, filename, target);
+        if (r < 0)
+                return log_error_errno(r, "Failed to move coredump %s into place: %m", target);
+
+        return 0;
+}
+
+static int maybe_remove_external_coredump(const char *filename, uint64_t size) {
+
+        /* Returns 1 if might remove, 0 if will not remove, < 0 on error. */
+
+        if (arg_storage == COREDUMP_STORAGE_EXTERNAL &&
+            size <= arg_external_size_max)
+                return 0;
+
+        if (!filename)
+                return 1;
+
+        if (unlink(filename) < 0 && errno != ENOENT)
+                return log_error_errno(errno, "Failed to unlink %s: %m", filename);
+
+        return 1;
+}
+
+static int make_filename(const Context *context, char **ret) {
+        _cleanup_free_ char *c = NULL, *u = NULL, *p = NULL, *t = NULL;
+        sd_id128_t boot = {};
+        int r;
+
+        assert(context);
+
+        c = filename_escape(context->meta[META_COMM]);
+        if (!c)
+                return -ENOMEM;
+
+        u = filename_escape(context->meta[META_ARGV_UID]);
+        if (!u)
+                return -ENOMEM;
+
+        r = sd_id128_get_boot(&boot);
+        if (r < 0)
+                return r;
+
+        p = filename_escape(context->meta[META_ARGV_PID]);
+        if (!p)
+                return -ENOMEM;
+
+        t = filename_escape(context->meta[META_ARGV_TIMESTAMP]);
+        if (!t)
+                return -ENOMEM;
+
+        if (asprintf(ret,
+                     "/var/lib/systemd/coredump/core.%s.%s." SD_ID128_FORMAT_STR ".%s.%s",
+                     c,
+                     u,
+                     SD_ID128_FORMAT_VAL(boot),
+                     p,
+                     t) < 0)
+                return -ENOMEM;
+
+        return 0;
+}
+
+#define _DEFINE_PARSE_AUXV(size, type, unaligned_read)                  \
+        static int parse_auxv##size(                                    \
+                        const void *auxv,                               \
+                        size_t size_bytes,                              \
+                        int *at_secure,                                 \
+                        uid_t *uid,                                     \
+                        uid_t *euid,                                    \
+                        gid_t *gid,                                     \
+                        gid_t *egid) {                                  \
+                                                                        \
+                assert(auxv || size_bytes == 0);                        \
+                                                                        \
+                if (size_bytes % (2 * sizeof(type)) != 0)               \
+                        return log_warning_errno(SYNTHETIC_ERRNO(EIO),  \
+                                                 "Incomplete auxv structure (%zu bytes).", \
+                                                 size_bytes);           \
+                                                                        \
+                size_t words = size_bytes / sizeof(type);               \
+                                                                        \
+                /* Note that we set output variables even on error. */  \
+                                                                        \
+                for (size_t i = 0; i + 1 < words; i += 2) {             \
+                        type key, val;                                  \
+                                                                        \
+                        key = unaligned_read((uint8_t*) auxv + i * sizeof(type)); \
+                        val = unaligned_read((uint8_t*) auxv + (i + 1) * sizeof(type)); \
+                                                                        \
+                        switch (key) {                                  \
+                        case AT_SECURE:                                 \
+                                *at_secure = val != 0;                  \
+                                break;                                  \
+                        case AT_UID:                                    \
+                                *uid = val;                             \
+                                break;                                  \
+                        case AT_EUID:                                   \
+                                *euid = val;                            \
+                                break;                                  \
+                        case AT_GID:                                    \
+                                *gid = val;                             \
+                                break;                                  \
+                        case AT_EGID:                                   \
+                                *egid = val;                            \
+                                break;                                  \
+                        case AT_NULL:                                   \
+                                if (val != 0)                           \
+                                        goto error;                     \
+                                return 0;                               \
+                        }                                               \
+                }                                                       \
+        error:                                                          \
+                return log_warning_errno(SYNTHETIC_ERRNO(ENODATA),      \
+                                         "AT_NULL terminator not found, cannot parse auxv structure."); \
+        }
+
+#define DEFINE_PARSE_AUXV(size)\
+        _DEFINE_PARSE_AUXV(size, uint##size##_t, unaligned_read_ne##size)
+
+DEFINE_PARSE_AUXV(32);
+DEFINE_PARSE_AUXV(64);
+
+static int grant_user_access(int core_fd, const Context *context) {
+        int at_secure = -1;
+        uid_t uid = UID_INVALID, euid = UID_INVALID;
+        uid_t gid = GID_INVALID, egid = GID_INVALID;
+        int r;
+
+        assert(core_fd >= 0);
+        assert(context);
+
+        if (!context->meta[META_PROC_AUXV])
+                return log_warning_errno(SYNTHETIC_ERRNO(ENODATA), "No auxv data, not adjusting permissions.");
+
+        uint8_t elf[EI_NIDENT];
+        errno = 0;
+        if (pread(core_fd, &elf, sizeof(elf), 0) != sizeof(elf))
+                return log_warning_errno(errno_or_else(EIO),
+                                         "Failed to pread from coredump fd: %s", STRERROR_OR_EOF(errno));
+
+        if (elf[EI_MAG0] != ELFMAG0 ||
+            elf[EI_MAG1] != ELFMAG1 ||
+            elf[EI_MAG2] != ELFMAG2 ||
+            elf[EI_MAG3] != ELFMAG3 ||
+            elf[EI_VERSION] != EV_CURRENT)
+                return log_info_errno(SYNTHETIC_ERRNO(EUCLEAN),
+                                      "Core file does not have ELF header, not adjusting permissions.");
+        if (!IN_SET(elf[EI_CLASS], ELFCLASS32, ELFCLASS64) ||
+            !IN_SET(elf[EI_DATA], ELFDATA2LSB, ELFDATA2MSB))
+                return log_info_errno(SYNTHETIC_ERRNO(EUCLEAN),
+                                      "Core file has strange ELF class, not adjusting permissions.");
+
+        if ((elf[EI_DATA] == ELFDATA2LSB) != (__BYTE_ORDER == __LITTLE_ENDIAN))
+                return log_info_errno(SYNTHETIC_ERRNO(EUCLEAN),
+                                      "Core file has non-native endianness, not adjusting permissions.");
+
+        if (elf[EI_CLASS] == ELFCLASS64)
+                r = parse_auxv64(context->meta[META_PROC_AUXV],
+                                 context->meta_size[META_PROC_AUXV],
+                                 &at_secure, &uid, &euid, &gid, &egid);
+        else
+                r = parse_auxv32(context->meta[META_PROC_AUXV],
+                                 context->meta_size[META_PROC_AUXV],
+                                 &at_secure, &uid, &euid, &gid, &egid);
+        if (r < 0)
+                return r;
+
+        /* We allow access if we got all the data and at_secure is not set and
+         * the uid/gid matches euid/egid. */
+        bool ret =
+                at_secure == 0 &&
+                uid != UID_INVALID && euid != UID_INVALID && uid == euid &&
+                gid != GID_INVALID && egid != GID_INVALID && gid == egid;
+        log_debug("Will %s access (uid="UID_FMT " euid="UID_FMT " gid="GID_FMT " egid="GID_FMT " at_secure=%s)",
+                  ret ? "permit" : "restrict",
+                  uid, euid, gid, egid, yes_no(at_secure));
+        return ret;
+}
+
+static int save_external_coredump(
+                const Context *context,
+                int input_fd,
+                char **ret_filename,
+                int *ret_node_fd,
+                int *ret_data_fd,
+                uint64_t *ret_size,
+                uint64_t *ret_compressed_size,
+                bool *ret_truncated) {
+
+        _cleanup_(unlink_and_freep) char *tmp = NULL;
+        _cleanup_free_ char *fn = NULL;
+        _cleanup_close_ int fd = -1;
+        uint64_t rlimit, process_limit, max_size;
+        bool truncated, storage_on_tmpfs;
+        struct stat st;
+        uid_t uid;
+        int r;
+
+        assert(context);
+        assert(ret_filename);
+        assert(ret_node_fd);
+        assert(ret_data_fd);
+        assert(ret_size);
+        assert(ret_compressed_size);
+        assert(ret_truncated);
+
+        r = parse_uid(context->meta[META_ARGV_UID], &uid);
+        if (r < 0)
+                return log_error_errno(r, "Failed to parse UID: %m");
+
+        r = safe_atou64(context->meta[META_ARGV_RLIMIT], &rlimit);
+        if (r < 0)
+                return log_error_errno(r, "Failed to parse resource limit '%s': %m",
+                                       context->meta[META_ARGV_RLIMIT]);
+        if (rlimit < page_size())
+                /* Is coredumping disabled? Then don't bother saving/processing the
+                 * coredump. Anything below PAGE_SIZE cannot give a readable coredump
+                 * (the kernel uses ELF_EXEC_PAGESIZE which is not easily accessible, but
+                 * is usually the same as PAGE_SIZE. */
+                return log_info_errno(SYNTHETIC_ERRNO(EBADSLT),
+                                      "Resource limits disable core dumping for process %s (%s).",
+                                      context->meta[META_ARGV_PID], context->meta[META_COMM]);
+
+        process_limit = MAX(arg_process_size_max, storage_size_max());
+        if (process_limit == 0)
+                return log_debug_errno(SYNTHETIC_ERRNO(EBADSLT),
+                                       "Limits for coredump processing and storage are both 0, not dumping core.");
+
+        /* Never store more than the process configured, or than we actually shall keep or process */
+        max_size = MIN(rlimit, process_limit);
+
+        r = make_filename(context, &fn);
+        if (r < 0)
+                return log_error_errno(r, "Failed to determine coredump file name: %m");
+
+        (void) mkdir_parents_label(fn, 0755);
+
+        fd = open_tmpfile_linkable(fn, O_RDWR|O_CLOEXEC, &tmp);
+        if (fd < 0)
+                return log_error_errno(fd, "Failed to create temporary file for coredump %s: %m", fn);
+
+        /* If storage is on tmpfs, the kernel oomd might kill us if there's MemoryMax set on
+         * the service or the slice it belongs to. This is common on low-resources systems,
+         * to avoid crashing processes to take away too many system resources.
+         * Check the cgroup settings, and set max_size to a bit less than half of the
+         * available memory left to the process.
+         * Then, attempt to write the core file uncompressed first - if the write gets
+         * interrupted, we know we won't be able to write it all, so instead compress what
+         * was written so far, delete the uncompressed truncated core, and then continue
+         * compressing from STDIN. Given the compressed core cannot be larger than the
+         * uncompressed one, and 1KB for metadata is accounted for in the calculation, we
+         * should be able to at least store the full compressed core file. */
+
+        storage_on_tmpfs = fd_is_temporary_fs(fd) > 0;
+        if (storage_on_tmpfs && arg_compress) {
+                _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
+                uint64_t cgroup_limit = UINT64_MAX;
+                struct statvfs sv;
+
+                /* If we can't get the cgroup limit, just ignore it, but don't fail,
+                 * try anyway with the config settings. */
+                r = sd_bus_default_system(&bus);
+                if (r < 0)
+                        log_info_errno(r, "Failed to connect to system bus, skipping MemoryAvailable check: %m");
+                else {
+                        _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
+
+                        r = sd_bus_get_property_trivial(
+                                        bus,
+                                        "org.freedesktop.systemd1",
+                                        "/org/freedesktop/systemd1/unit/self",
+                                        "org.freedesktop.systemd1.Service",
+                                        "MemoryAvailable",
+                                        &error,
+                                        't', &cgroup_limit);
+                        if (r < 0)
+                                log_warning_errno(r,
+                                                  "Failed to query MemoryAvailable for current unit, "
+                                                  "falling back to static config settings: %s",
+                                                  bus_error_message(&error, r));
+                }
+
+                max_size = MIN(cgroup_limit, max_size);
+                max_size = LESS_BY(max_size, 1024U) / 2; /* Account for 1KB metadata overhead for compressing */
+                max_size = MAX(PROCESS_SIZE_MIN, max_size); /* Impose a lower minimum */
+
+                /* tmpfs might get full quickly, so check the available space too.
+                 * But don't worry about errors here, failing to access the storage
+                 * location will be better logged when writing to it. */
+                if (statvfs("/var/lib/systemd/coredump/", &sv) >= 0)
+                        max_size = MIN((uint64_t)sv.f_frsize * (uint64_t)sv.f_bfree, max_size);
+
+                log_debug("Limiting core file size to %" PRIu64 " bytes due to cgroup memory limits.", max_size);
+        }
+
+        r = copy_bytes(input_fd, fd, max_size, 0);
+        if (r < 0)
+                return log_error_errno(r, "Cannot store coredump of %s (%s): %m",
+                                context->meta[META_ARGV_PID], context->meta[META_COMM]);
+        truncated = r == 1;
+
+        bool allow_user = grant_user_access(fd, context) > 0;
+
+#if HAVE_COMPRESSION
+        if (arg_compress) {
+                _cleanup_(unlink_and_freep) char *tmp_compressed = NULL;
+                _cleanup_free_ char *fn_compressed = NULL;
+                _cleanup_close_ int fd_compressed = -1;
+                uint64_t uncompressed_size = 0;
+
+                if (lseek(fd, 0, SEEK_SET) == (off_t) -1)
+                        return log_error_errno(errno, "Failed to seek on coredump %s: %m", fn);
+
+                fn_compressed = strjoin(fn, default_compression_extension());
+                if (!fn_compressed)
+                        return log_oom();
+
+                fd_compressed = open_tmpfile_linkable(fn_compressed, O_RDWR|O_CLOEXEC, &tmp_compressed);
+                if (fd_compressed < 0)
+                        return log_error_errno(fd_compressed, "Failed to create temporary file for coredump %s: %m", fn_compressed);
+
+                r = compress_stream(fd, fd_compressed, max_size, &uncompressed_size);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to compress %s: %m", coredump_tmpfile_name(tmp_compressed));
+
+                if (truncated && storage_on_tmpfs) {
+                        uint64_t partial_uncompressed_size = 0;
+
+                        /* Uncompressed write was truncated and we are writing to tmpfs: delete
+                         * the uncompressed core, and compress the remaining part from STDIN. */
+
+                        tmp = unlink_and_free(tmp);
+                        fd = safe_close(fd);
+
+                        r = compress_stream(input_fd, fd_compressed, max_size, &partial_uncompressed_size);
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to compress %s: %m", coredump_tmpfile_name(tmp_compressed));
+                        uncompressed_size += partial_uncompressed_size;
+                }
+
+                r = fix_permissions(fd_compressed, tmp_compressed, fn_compressed, context, uid, allow_user);
+                if (r < 0)
+                        return r;
+
+                if (fstat(fd_compressed, &st) < 0)
+                        return log_error_errno(errno,
+                                        "Failed to fstat core file %s: %m",
+                                        coredump_tmpfile_name(tmp_compressed));
+
+                *ret_filename = TAKE_PTR(fn_compressed);       /* compressed */
+                *ret_node_fd = TAKE_FD(fd_compressed);         /* compressed */
+                *ret_compressed_size = (uint64_t) st.st_size;  /* compressed */
+                *ret_data_fd = TAKE_FD(fd);
+                *ret_size = uncompressed_size;
+                *ret_truncated = truncated;
+                tmp_compressed = mfree(tmp_compressed);
+
+                return 0;
+        }
+#endif
+
+        if (truncated)
+                log_struct(LOG_INFO,
+                           LOG_MESSAGE("Core file was truncated to %"PRIu64" bytes.", max_size),
+                           "SIZE_LIMIT=%"PRIu64, max_size,
+                           "MESSAGE_ID=" SD_MESSAGE_TRUNCATED_CORE_STR);
+
+        r = fix_permissions(fd, tmp, fn, context, uid, allow_user);
+        if (r < 0)
+                return log_error_errno(r, "Failed to fix permissions and finalize coredump %s into %s: %m", coredump_tmpfile_name(tmp), fn);
+
+        if (fstat(fd, &st) < 0)
+                return log_error_errno(errno, "Failed to fstat core file %s: %m", coredump_tmpfile_name(tmp));
+
+        if (lseek(fd, 0, SEEK_SET) == (off_t) -1)
+                return log_error_errno(errno, "Failed to seek on coredump %s: %m", fn);
+
+        *ret_filename = TAKE_PTR(fn);
+        *ret_data_fd = TAKE_FD(fd);
+        *ret_size = (uint64_t) st.st_size;
+        *ret_truncated = truncated;
+
+        return 0;
+}
+
+static int allocate_journal_field(int fd, size_t size, char **ret, size_t *ret_size) {
+        _cleanup_free_ char *field = NULL;
+        ssize_t n;
+
+        assert(fd >= 0);
+        assert(ret);
+        assert(ret_size);
+
+        if (lseek(fd, 0, SEEK_SET) == (off_t) -1)
+                return log_warning_errno(errno, "Failed to seek: %m");
+
+        field = malloc(9 + size);
+        if (!field)
+                return log_warning_errno(SYNTHETIC_ERRNO(ENOMEM),
+                                         "Failed to allocate memory for coredump, coredump will not be stored.");
+
+        memcpy(field, "COREDUMP=", 9);
+
+        /* NB: simple read() would fail for overly large coredumps, since read() on Linux can only deal with
+         * 0x7ffff000 bytes max. Hence call things in a loop. */
+        n = loop_read(fd, field + 9, size, /* do_poll= */ false);
+        if (n < 0)
+                return log_error_errno((int) n, "Failed to read core data: %m");
+        if ((size_t) n < size)
+                return log_error_errno(SYNTHETIC_ERRNO(EIO),
+                                       "Core data too short.");
+
+        *ret = TAKE_PTR(field);
+        *ret_size = size + 9;
+
+        return 0;
+}
+
+/* Joins /proc/[pid]/fd/ and /proc/[pid]/fdinfo/ into the following lines:
+ * 0:/dev/pts/23
+ * pos:    0
+ * flags:  0100002
+ *
+ * 1:/dev/pts/23
+ * pos:    0
+ * flags:  0100002
+ *
+ * 2:/dev/pts/23
+ * pos:    0
+ * flags:  0100002
+ * EOF
+ */
+static int compose_open_fds(pid_t pid, char **open_fds) {
+        _cleanup_closedir_ DIR *proc_fd_dir = NULL;
+        _cleanup_close_ int proc_fdinfo_fd = -1;
+        _cleanup_free_ char *buffer = NULL;
+        _cleanup_fclose_ FILE *stream = NULL;
+        const char *fddelim = "", *path;
+        size_t size = 0;
+        int r;
+
+        assert(pid >= 0);
+        assert(open_fds != NULL);
+
+        path = procfs_file_alloca(pid, "fd");
+        proc_fd_dir = opendir(path);
+        if (!proc_fd_dir)
+                return -errno;
+
+        proc_fdinfo_fd = openat(dirfd(proc_fd_dir), "../fdinfo", O_DIRECTORY|O_NOFOLLOW|O_CLOEXEC|O_PATH);
+        if (proc_fdinfo_fd < 0)
+                return -errno;
+
+        stream = open_memstream_unlocked(&buffer, &size);
+        if (!stream)
+                return -ENOMEM;
+
+        FOREACH_DIRENT(de, proc_fd_dir, return -errno) {
+                _cleanup_fclose_ FILE *fdinfo = NULL;
+                _cleanup_free_ char *fdname = NULL;
+                _cleanup_close_ int fd = -1;
+
+                r = readlinkat_malloc(dirfd(proc_fd_dir), de->d_name, &fdname);
+                if (r < 0)
+                        return r;
+
+                fprintf(stream, "%s%s:%s\n", fddelim, de->d_name, fdname);
+                fddelim = "\n";
+
+                /* Use the directory entry from /proc/[pid]/fd with /proc/[pid]/fdinfo */
+                fd = openat(proc_fdinfo_fd, de->d_name, O_NOFOLLOW|O_CLOEXEC|O_RDONLY);
+                if (fd < 0)
+                        continue;
+
+                fdinfo = take_fdopen(&fd, "r");
+                if (!fdinfo)
+                        continue;
+
+                for (;;) {
+                        _cleanup_free_ char *line = NULL;
+
+                        r = read_line(fdinfo, LONG_LINE_MAX, &line);
+                        if (r < 0)
+                                return r;
+                        if (r == 0)
+                                break;
+
+                        fputs(line, stream);
+                        fputc('\n', stream);
+                }
+        }
+
+        errno = 0;
+        stream = safe_fclose(stream);
+
+        if (errno > 0)
+                return -errno;
+
+        *open_fds = TAKE_PTR(buffer);
+
+        return 0;
+}
+
+static int get_process_ns(pid_t pid, const char *namespace, ino_t *ns) {
+        const char *p;
+        struct stat stbuf;
+        _cleanup_close_ int proc_ns_dir_fd = -1;
+
+        p = procfs_file_alloca(pid, "ns");
+
+        proc_ns_dir_fd = open(p, O_DIRECTORY | O_CLOEXEC | O_RDONLY);
+        if (proc_ns_dir_fd < 0)
+                return -errno;
+
+        if (fstatat(proc_ns_dir_fd, namespace, &stbuf, /* flags */0) < 0)
+                return -errno;
+
+        *ns = stbuf.st_ino;
+        return 0;
+}
+
+static int get_mount_namespace_leader(pid_t pid, pid_t *ret) {
+        ino_t proc_mntns;
+        int r;
+
+        r = get_process_ns(pid, "mnt", &proc_mntns);
+        if (r < 0)
+                return r;
+
+        for (;;) {
+                ino_t parent_mntns;
+                pid_t ppid;
+
+                r = get_process_ppid(pid, &ppid);
+                if (r == -EADDRNOTAVAIL) /* Reached the top (i.e. typically PID 1, but could also be a process
+                                          * whose parent is not in our pidns) */
+                        return -ENOENT;
+                if (r < 0)
+                        return r;
+
+                r = get_process_ns(ppid, "mnt", &parent_mntns);
+                if (r < 0)
+                        return r;
+
+                if (proc_mntns != parent_mntns) {
+                        *ret = ppid;
+                        return 0;
+                }
+
+                pid = ppid;
+        }
+}
+
+/* Returns 1 if the parent was found.
+ * Returns 0 if there is not a process we can call the pid's
+ * container parent (the pid's process isn't 'containerized').
+ * Returns a negative number on errors.
+ */
+static int get_process_container_parent_cmdline(pid_t pid, char** cmdline) {
+        pid_t container_pid;
+        const char *proc_root_path;
+        struct stat root_stat, proc_root_stat;
+        int r;
+
+        /* To compare inodes of / and /proc/[pid]/root */
+        if (stat("/", &root_stat) < 0)
+                return -errno;
+
+        proc_root_path = procfs_file_alloca(pid, "root");
+        if (stat(proc_root_path, &proc_root_stat) < 0)
+                return -errno;
+
+        /* The process uses system root. */
+        if (stat_inode_same(&proc_root_stat, &root_stat)) {
+                *cmdline = NULL;
+                return 0;
+        }
+
+        r = get_mount_namespace_leader(pid, &container_pid);
+        if (r < 0)
+                return r;
+
+        r = get_process_cmdline(container_pid, SIZE_MAX, PROCESS_CMDLINE_QUOTE_POSIX, cmdline);
+        if (r < 0)
+                return r;
+
+        return 1;
+}
+
+static int change_uid_gid(const Context *context) {
+        uid_t uid;
+        gid_t gid;
+        int r;
+
+        r = parse_uid(context->meta[META_ARGV_UID], &uid);
+        if (r < 0)
+                return r;
+
+        if (uid_is_system(uid)) {
+                const char *user = "systemd-coredump";
+
+                r = get_user_creds(&user, &uid, &gid, NULL, NULL, 0);
+                if (r < 0) {
+                        log_warning_errno(r, "Cannot resolve %s user. Proceeding to dump core as root: %m", user);
+                        uid = gid = 0;
+                }
+        } else {
+                r = parse_gid(context->meta[META_ARGV_GID], &gid);
+                if (r < 0)
+                        return r;
+        }
+
+        return drop_privileges(uid, gid, 0);
+}
+
+static int submit_coredump(
+                const Context *context,
+                struct iovec_wrapper *iovw,
+                int input_fd) {
+
+        _cleanup_(json_variant_unrefp) JsonVariant *json_metadata = NULL;
+        _cleanup_close_ int coredump_fd = -1, coredump_node_fd = -1;
+        _cleanup_free_ char *filename = NULL, *coredump_data = NULL;
+        _cleanup_free_ char *stacktrace = NULL;
+        const char *module_name;
+        uint64_t coredump_size = UINT64_MAX, coredump_compressed_size = UINT64_MAX;
+        bool truncated = false, written = false;
+        JsonVariant *module_json;
+        int r;
+
+        assert(context);
+        assert(iovw);
+        assert(input_fd >= 0);
+
+        /* Vacuum before we write anything again */
+        (void) coredump_vacuum(-1, arg_keep_free, arg_max_use);
+
+        /* Always stream the coredump to disk, if that's possible */
+        written = save_external_coredump(
+                        context, input_fd,
+                        &filename, &coredump_node_fd, &coredump_fd,
+                        &coredump_size, &coredump_compressed_size, &truncated) >= 0;
+        if (written) {
+                /* If we could write it to disk we can now process it. */
+                /* If we don't want to keep the coredump on disk, remove it now, as later on we
+                 * will lack the privileges for it. However, we keep the fd to it, so that we can
+                 * still process it and log it. */
+                r = maybe_remove_external_coredump(filename, coredump_node_fd >= 0 ? coredump_compressed_size : coredump_size);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        (void) iovw_put_string_field(iovw, "COREDUMP_FILENAME=", filename);
+                else if (arg_storage == COREDUMP_STORAGE_EXTERNAL)
+                        log_info("The core will not be stored: size %"PRIu64" is greater than %"PRIu64" (the configured maximum)",
+                                 coredump_node_fd >= 0 ? coredump_compressed_size : coredump_size, arg_external_size_max);
+
+                /* Vacuum again, but exclude the coredump we just created */
+                (void) coredump_vacuum(coredump_node_fd >= 0 ? coredump_node_fd : coredump_fd, arg_keep_free, arg_max_use);
+        }
+
+        /* Now, let's drop privileges to become the user who owns the segfaulted process and allocate the
+         * coredump memory under the user's uid. This also ensures that the credentials journald will see are
+         * the ones of the coredumping user, thus making sure the user gets access to the core dump. Let's
+         * also get rid of all capabilities, if we run as root, we won't need them anymore. */
+        r = change_uid_gid(context);
+        if (r < 0)
+                return log_error_errno(r, "Failed to drop privileges: %m");
+
+        if (written) {
+                /* Try to get a stack trace if we can */
+                if (coredump_size > arg_process_size_max)
+                        log_debug("Not generating stack trace: core size %"PRIu64" is greater "
+                                  "than %"PRIu64" (the configured maximum)",
+                                  coredump_size, arg_process_size_max);
+                else if (coredump_fd >= 0) {
+                        bool skip = startswith(context->meta[META_COMM], "systemd-coredum"); /* COMM is 16 bytes usually */
+
+                        (void) parse_elf_object(coredump_fd,
+                                                context->meta[META_EXE],
+                                                /* fork_disable_dump= */ skip, /* avoid loops */
+                                                &stacktrace,
+                                                &json_metadata);
+                }
+        }
+
+        _cleanup_free_ char *core_message = NULL;
+        core_message = strjoin(
+                        "Process ", context->meta[META_ARGV_PID],
+                        " (", context->meta[META_COMM],
+                        ") of user ", context->meta[META_ARGV_UID],
+                        written ? " dumped core." : " terminated abnormally without generating a coredump.");
+        if (!core_message)
+                return log_oom();
+
+        if (context->is_journald && filename)
+                if (!strextend(&core_message, "\nCoredump diverted to ", filename))
+                        return log_oom();
+
+        if (stacktrace)
+                if (!strextend(&core_message, "\n\n", stacktrace))
+                        return log_oom();
+
+        if (context->is_journald)
+                /* We might not be able to log to the journal, so let's always print the message to another
+                 * log target. The target was set previously to something safe. */
+                log_dispatch(LOG_ERR, 0, core_message);
+
+        (void) iovw_put_string_field(iovw, "MESSAGE=", core_message);
+
+        if (truncated)
+                (void) iovw_put_string_field(iovw, "COREDUMP_TRUNCATED=", "1");
+
+        /* If we managed to parse any ELF metadata (build-id, ELF package meta),
+         * attach it as journal metadata. */
+        if (json_metadata) {
+                _cleanup_free_ char *formatted_json = NULL;
+
+                r = json_variant_format(json_metadata, 0, &formatted_json);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to format JSON package metadata: %m");
+
+                (void) iovw_put_string_field(iovw, "COREDUMP_PACKAGE_JSON=", formatted_json);
+        }
+
+        /* In the unlikely scenario that context->meta[META_EXE] is not available,
+         * let's avoid guessing the module name and skip the loop. */
+        if (context->meta[META_EXE])
+                JSON_VARIANT_OBJECT_FOREACH(module_name, module_json, json_metadata) {
+                        JsonVariant *t;
+
+                        /* We only add structured fields for the 'main' ELF module, and only if we can identify it. */
+                        if (!path_equal_filename(module_name, context->meta[META_EXE]))
+                                continue;
+
+                        t = json_variant_by_key(module_json, "name");
+                        if (t)
+                                (void) iovw_put_string_field(iovw, "COREDUMP_PACKAGE_NAME=", json_variant_string(t));
+
+                        t = json_variant_by_key(module_json, "version");
+                        if (t)
+                                (void) iovw_put_string_field(iovw, "COREDUMP_PACKAGE_VERSION=", json_variant_string(t));
+                }
+
+        /* Optionally store the entire coredump in the journal */
+        if (arg_storage == COREDUMP_STORAGE_JOURNAL && coredump_fd >= 0) {
+                if (coredump_size <= arg_journal_size_max) {
+                        size_t sz = 0;
+
+                        /* Store the coredump itself in the journal */
+
+                        r = allocate_journal_field(coredump_fd, (size_t) coredump_size, &coredump_data, &sz);
+                        if (r >= 0) {
+                                if (iovw_put(iovw, coredump_data, sz) >= 0)
+                                        TAKE_PTR(coredump_data);
+                        } else
+                                log_warning_errno(r, "Failed to attach the core to the journal entry: %m");
+                } else
+                        log_info("The core will not be stored: size %"PRIu64" is greater than %"PRIu64" (the configured maximum)",
+                                 coredump_size, arg_journal_size_max);
+        }
+
+        /* If journald is coredumping, we have to be careful that we don't deadlock when trying to write the
+         * coredump to the journal, so we put the journal socket in nonblocking mode before trying to write
+         * the coredump to the socket. */
+
+        if (context->is_journald) {
+                r = journal_fd_nonblock(true);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to make journal socket non-blocking: %m");
+        }
+
+        r = sd_journal_sendv(iovw->iovec, iovw->count);
+
+        if (context->is_journald) {
+                int k;
+
+                k = journal_fd_nonblock(false);
+                if (k < 0)
+                        return log_error_errno(k, "Failed to make journal socket blocking: %m");
+        }
+
+        if (r == -EAGAIN && context->is_journald)
+                log_warning_errno(r, "Failed to log journal coredump, ignoring: %m");
+        else if (r < 0)
+                return log_error_errno(r, "Failed to log coredump: %m");
+
+        return 0;
+}
+
+static int save_context(Context *context, const struct iovec_wrapper *iovw) {
+        const char *unit;
+        int r;
+
+        assert(context);
+        assert(iovw);
+        assert(iovw->count >= _META_ARGV_MAX);
+
+        /* The context does not allocate any memory on its own */
+
+        for (size_t n = 0; n < iovw->count; n++) {
+                struct iovec *iovec = iovw->iovec + n;
+
+                for (size_t i = 0; i < ELEMENTSOF(meta_field_names); i++) {
+                        /* Note that these strings are NUL terminated, because we made sure that a
+                         * trailing NUL byte is in the buffer, though not included in the iov_len
+                         * count (see process_socket() and gather_pid_metadata_*()) */
+                        assert(((char*) iovec->iov_base)[iovec->iov_len] == 0);
+
+                        const char *p = startswith(iovec->iov_base, meta_field_names[i]);
+                        if (p) {
+                                context->meta[i] = p;
+                                context->meta_size[i] = iovec->iov_len - strlen(meta_field_names[i]);
+                                break;
+                        }
+                }
+        }
+
+        if (!context->meta[META_ARGV_PID])
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
+                                       "Failed to find the PID of crashing process");
+
+        r = parse_pid(context->meta[META_ARGV_PID], &context->pid);
+        if (r < 0)
+                return log_error_errno(r, "Failed to parse PID \"%s\": %m", context->meta[META_ARGV_PID]);
+
+        unit = context->meta[META_UNIT];
+        context->is_pid1 = streq(context->meta[META_ARGV_PID], "1") || streq_ptr(unit, SPECIAL_INIT_SCOPE);
+        context->is_journald = streq_ptr(unit, SPECIAL_JOURNALD_SERVICE);
+
+        return 0;
+}
+
+static int process_socket(int fd) {
+        _cleanup_close_ int input_fd = -1;
+        Context context = {};
+        struct iovec_wrapper iovw = {};
+        struct iovec iovec;
+        int r;
+
+        assert(fd >= 0);
+
+        log_setup();
+
+        log_debug("Processing coredump received on stdin...");
+
+        for (;;) {
+                CMSG_BUFFER_TYPE(CMSG_SPACE(sizeof(int))) control;
+                struct msghdr mh = {
+                        .msg_control = &control,
+                        .msg_controllen = sizeof(control),
+                        .msg_iovlen = 1,
+                };
+                ssize_t n;
+                ssize_t l;
+
+                l = next_datagram_size_fd(fd);
+                if (l < 0) {
+                        r = log_error_errno(l, "Failed to determine datagram size to read: %m");
+                        goto finish;
+                }
+
+                iovec.iov_len = l;
+                iovec.iov_base = malloc(l + 1);
+                if (!iovec.iov_base) {
+                        r = log_oom();
+                        goto finish;
+                }
+
+                mh.msg_iov = &iovec;
+
+                n = recvmsg_safe(fd, &mh, MSG_CMSG_CLOEXEC);
+                if (n < 0)  {
+                        free(iovec.iov_base);
+                        r = log_error_errno(n, "Failed to receive datagram: %m");
+                        goto finish;
+                }
+
+                /* The final zero-length datagram carries the file descriptor and tells us
+                 * that we're done. */
+                if (n == 0) {
+                        struct cmsghdr *found;
+
+                        free(iovec.iov_base);
+
+                        found = cmsg_find(&mh, SOL_SOCKET, SCM_RIGHTS, CMSG_LEN(sizeof(int)));
+                        if (!found) {
+                                cmsg_close_all(&mh);
+                                r = log_error_errno(SYNTHETIC_ERRNO(EBADMSG),
+                                                    "Coredump file descriptor missing.");
+                                goto finish;
+                        }
+
+                        assert(input_fd < 0);
+                        input_fd = *(int*) CMSG_DATA(found);
+                        break;
+                } else
+                        cmsg_close_all(&mh);
+
+                /* Add trailing NUL byte, in case these are strings */
+                ((char*) iovec.iov_base)[n] = 0;
+                iovec.iov_len = (size_t) n;
+
+                r = iovw_put(&iovw, iovec.iov_base, iovec.iov_len);
+                if (r < 0)
+                        goto finish;
+        }
+
+        /* Make sure we got all data we really need */
+        assert(input_fd >= 0);
+
+        r = save_context(&context, &iovw);
+        if (r < 0)
+                goto finish;
+
+        /* Make sure we received at least all fields we need. */
+        for (int i = 0; i < _META_MANDATORY_MAX; i++)
+                if (!context.meta[i]) {
+                        r = log_error_errno(SYNTHETIC_ERRNO(EINVAL),
+                                            "A mandatory argument (%i) has not been sent, aborting.",
+                                            i);
+                        goto finish;
+                }
+
+        r = submit_coredump(&context, &iovw, input_fd);
+
+finish:
+        iovw_free_contents(&iovw, true);
+        return r;
+}
+
+static int send_iovec(const struct iovec_wrapper *iovw, int input_fd) {
+        _cleanup_close_ int fd = -1;
+        int r;
+
+        assert(iovw);
+        assert(input_fd >= 0);
+
+        fd = socket(AF_UNIX, SOCK_SEQPACKET|SOCK_CLOEXEC, 0);
+        if (fd < 0)
+                return log_error_errno(errno, "Failed to create coredump socket: %m");
+
+        r = connect_unix_path(fd, AT_FDCWD, "/run/systemd/coredump");
+        if (r < 0)
+                return log_error_errno(r, "Failed to connect to coredump service: %m");
+
+        for (size_t i = 0; i < iovw->count; i++) {
+                struct msghdr mh = {
+                        .msg_iov = iovw->iovec + i,
+                        .msg_iovlen = 1,
+                };
+                struct iovec copy[2];
+
+                for (;;) {
+                        if (sendmsg(fd, &mh, MSG_NOSIGNAL) >= 0)
+                                break;
+
+                        if (errno == EMSGSIZE && mh.msg_iov[0].iov_len > 0) {
+                                /* This field didn't fit? That's a pity. Given that this is
+                                 * just metadata, let's truncate the field at half, and try
+                                 * again. We append three dots, in order to show that this is
+                                 * truncated. */
+
+                                if (mh.msg_iov != copy) {
+                                        /* We don't want to modify the caller's iovec, hence
+                                         * let's create our own array, consisting of two new
+                                         * iovecs, where the first is a (truncated) copy of
+                                         * what we want to send, and the second one contains
+                                         * the trailing dots. */
+                                        copy[0] = iovw->iovec[i];
+                                        copy[1] = IOVEC_MAKE(((char[]){'.', '.', '.'}), 3);
+
+                                        mh.msg_iov = copy;
+                                        mh.msg_iovlen = 2;
+                                }
+
+                                copy[0].iov_len /= 2; /* halve it, and try again */
+                                continue;
+                        }
+
+                        return log_error_errno(errno, "Failed to send coredump datagram: %m");
+                }
+        }
+
+        r = send_one_fd(fd, input_fd, 0);
+        if (r < 0)
+                return log_error_errno(r, "Failed to send coredump fd: %m");
+
+        return 0;
+}
+
+static int gather_pid_metadata_from_argv(
+                struct iovec_wrapper *iovw,
+                Context *context,
+                int argc, char **argv) {
+
+        _cleanup_free_ char *free_timestamp = NULL;
+        int r, signo;
+        char *t;
+
+        /* We gather all metadata that were passed via argv[] into an array of iovecs that
+         * we'll forward to the socket unit */
+
+        if (argc < _META_ARGV_MAX)
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
+                                       "Not enough arguments passed by the kernel (%i, expected %i).",
+                                       argc, _META_ARGV_MAX);
+
+        for (int i = 0; i < _META_ARGV_MAX; i++) {
+
+                t = argv[i];
+
+                switch (i) {
+
+                case META_ARGV_TIMESTAMP:
+                        /* The journal fields contain the timestamp padded with six
+                         * zeroes, so that the kernel-supplied 1s granularity timestamps
+                         * becomes 1µs granularity, i.e. the granularity systemd usually
+                         * operates in. */
+                        t = free_timestamp = strjoin(argv[i], "000000");
+                        if (!t)
+                                return log_oom();
+                        break;
+
+                case META_ARGV_SIGNAL:
+                        /* For signal, record its pretty name too */
+                        if (safe_atoi(argv[i], &signo) >= 0 && SIGNAL_VALID(signo))
+                                (void) iovw_put_string_field(iovw, "COREDUMP_SIGNAL_NAME=SIG",
+                                                             signal_to_string(signo));
+                        break;
+
+                default:
+                        break;
+                }
+
+                r = iovw_put_string_field(iovw, meta_field_names[i], t);
+                if (r < 0)
+                        return r;
+        }
+
+        /* Cache some of the process metadata we collected so far and that we'll need to
+         * access soon */
+        return save_context(context, iovw);
+}
+
+static int gather_pid_metadata(struct iovec_wrapper *iovw, Context *context) {
+        uid_t owner_uid;
+        pid_t pid;
+        char *t;
+        size_t size;
+        const char *p;
+        int r;
+
+        /* Note that if we fail on oom later on, we do not roll-back changes to the iovec
+         * structure. (It remains valid, with the first iovec fields initialized.) */
+
+        pid = context->pid;
+
+        /* The following is mandatory */
+        r = get_process_comm(pid, &t);
+        if (r < 0)
+                return log_error_errno(r, "Failed to get COMM: %m");
+
+        r = iovw_put_string_field_free(iovw, "COREDUMP_COMM=", t);
+        if (r < 0)
+                return r;
+
+        /* The following are optional, but we use them if present. */
+        r = get_process_exe(pid, &t);
+        if (r >= 0)
+                r = iovw_put_string_field_free(iovw, "COREDUMP_EXE=", t);
+        if (r < 0)
+                log_warning_errno(r, "Failed to get EXE, ignoring: %m");
+
+        if (cg_pid_get_unit(pid, &t) >= 0)
+                (void) iovw_put_string_field_free(iovw, "COREDUMP_UNIT=", t);
+
+        if (cg_pid_get_user_unit(pid, &t) >= 0)
+                (void) iovw_put_string_field_free(iovw, "COREDUMP_USER_UNIT=", t);
+
+        if (sd_pid_get_session(pid, &t) >= 0)
+                (void) iovw_put_string_field_free(iovw, "COREDUMP_SESSION=", t);
+
+        if (sd_pid_get_owner_uid(pid, &owner_uid) >= 0) {
+                r = asprintf(&t, UID_FMT, owner_uid);
+                if (r > 0)
+                        (void) iovw_put_string_field_free(iovw, "COREDUMP_OWNER_UID=", t);
+        }
+
+        if (sd_pid_get_slice(pid, &t) >= 0)
+                (void) iovw_put_string_field_free(iovw, "COREDUMP_SLICE=", t);
+
+        if (get_process_cmdline(pid, SIZE_MAX, PROCESS_CMDLINE_QUOTE_POSIX, &t) >= 0)
+                (void) iovw_put_string_field_free(iovw, "COREDUMP_CMDLINE=", t);
+
+        if (cg_pid_get_path_shifted(pid, NULL, &t) >= 0)
+                (void) iovw_put_string_field_free(iovw, "COREDUMP_CGROUP=", t);
+
+        if (compose_open_fds(pid, &t) >= 0)
+                (void) iovw_put_string_field_free(iovw, "COREDUMP_OPEN_FDS=", t);
+
+        p = procfs_file_alloca(pid, "status");
+        if (read_full_virtual_file(p, &t, NULL) >= 0)
+                (void) iovw_put_string_field_free(iovw, "COREDUMP_PROC_STATUS=", t);
+
+        p = procfs_file_alloca(pid, "maps");
+        if (read_full_virtual_file(p, &t, NULL) >= 0)
+                (void) iovw_put_string_field_free(iovw, "COREDUMP_PROC_MAPS=", t);
+
+        p = procfs_file_alloca(pid, "limits");
+        if (read_full_virtual_file(p, &t, NULL) >= 0)
+                (void) iovw_put_string_field_free(iovw, "COREDUMP_PROC_LIMITS=", t);
+
+        p = procfs_file_alloca(pid, "cgroup");
+        if (read_full_virtual_file(p, &t, NULL) >= 0)
+                (void) iovw_put_string_field_free(iovw, "COREDUMP_PROC_CGROUP=", t);
+
+        p = procfs_file_alloca(pid, "mountinfo");
+        if (read_full_virtual_file(p, &t, NULL) >= 0)
+                (void) iovw_put_string_field_free(iovw, "COREDUMP_PROC_MOUNTINFO=", t);
+
+        /* We attach /proc/auxv here. ELF coredumps also contain a note for this (NT_AUXV), see elf(5). */
+        p = procfs_file_alloca(pid, "auxv");
+        if (read_full_virtual_file(p, &t, &size) >= 0) {
+                char *buf = malloc(strlen("COREDUMP_PROC_AUXV=") + size + 1);
+                if (buf) {
+                        /* Add a dummy terminator to make save_context() happy. */
+                        *((uint8_t*) mempcpy(stpcpy(buf, "COREDUMP_PROC_AUXV="), t, size)) = '\0';
+                        (void) iovw_consume(iovw, buf, size + strlen("COREDUMP_PROC_AUXV="));
+                }
+
+                free(t);
+        }
+
+        if (get_process_cwd(pid, &t) >= 0)
+                (void) iovw_put_string_field_free(iovw, "COREDUMP_CWD=", t);
+
+        if (get_process_root(pid, &t) >= 0) {
+                bool proc_self_root_is_slash;
+
+                proc_self_root_is_slash = strcmp(t, "/") == 0;
+
+                (void) iovw_put_string_field_free(iovw, "COREDUMP_ROOT=", t);
+
+                /* If the process' root is "/", then there is a chance it has
+                 * mounted own root and hence being containerized. */
+                if (proc_self_root_is_slash && get_process_container_parent_cmdline(pid, &t) > 0)
+                        (void) iovw_put_string_field_free(iovw, "COREDUMP_CONTAINER_CMDLINE=", t);
+        }
+
+        if (get_process_environ(pid, &t) >= 0)
+                (void) iovw_put_string_field_free(iovw, "COREDUMP_ENVIRON=", t);
+
+        /* we successfully acquired all metadata */
+        return save_context(context, iovw);
+}
+
+static int process_kernel(int argc, char* argv[]) {
+        Context context = {};
+        struct iovec_wrapper *iovw;
+        int r;
+
+        /* When we're invoked by the kernel, stdout/stderr are closed which is dangerous because the fds
+         * could get reallocated. To avoid hard to debug issues, let's instead bind stdout/stderr to
+         * /dev/null. */
+        r = rearrange_stdio(STDIN_FILENO, -1, -1);
+        if (r < 0)
+                return log_error_errno(r, "Failed to connect stdout/stderr to /dev/null: %m");
+
+        log_debug("Processing coredump received from the kernel...");
+
+        iovw = iovw_new();
+        if (!iovw)
+                return log_oom();
+
+        (void) iovw_put_string_field(iovw, "MESSAGE_ID=", SD_MESSAGE_COREDUMP_STR);
+        (void) iovw_put_string_field(iovw, "PRIORITY=", STRINGIFY(LOG_CRIT));
+
+        /* Collect all process metadata passed by the kernel through argv[] */
+        r = gather_pid_metadata_from_argv(iovw, &context, argc - 1, argv + 1);
+        if (r < 0)
+                goto finish;
+
+        /* Collect the rest of the process metadata retrieved from the runtime */
+        r = gather_pid_metadata(iovw, &context);
+        if (r < 0)
+                goto finish;
+
+        if (!context.is_journald) {
+                /* OK, now we know it's not the journal, hence we can make use of it now. */
+                log_set_target(LOG_TARGET_JOURNAL_OR_KMSG);
+                log_open();
+        }
+
+        /* If this is PID 1 disable coredump collection, we'll unlikely be able to process
+         * it later on.
+         *
+         * FIXME: maybe we should disable coredumps generation from the beginning and
+         * re-enable it only when we know it's either safe (ie we're not running OOM) or
+         * it's not pid1 ? */
+        if (context.is_pid1) {
+                log_notice("Due to PID 1 having crashed coredump collection will now be turned off.");
+                disable_coredumps();
+        }
+
+        if (context.is_journald || context.is_pid1)
+                r = submit_coredump(&context, iovw, STDIN_FILENO);
+        else
+                r = send_iovec(iovw, STDIN_FILENO);
+
+ finish:
+        iovw = iovw_free_free(iovw);
+        return r;
+}
+
+static int process_backtrace(int argc, char *argv[]) {
+        Context context = {};
+        struct iovec_wrapper *iovw;
+        char *message;
+        int r;
+         _cleanup_(journal_importer_cleanup) JournalImporter importer = JOURNAL_IMPORTER_INIT(STDIN_FILENO);
+
+        log_debug("Processing backtrace on stdin...");
+
+        iovw = iovw_new();
+        if (!iovw)
+                return log_oom();
+
+        (void) iovw_put_string_field(iovw, "MESSAGE_ID=", SD_MESSAGE_BACKTRACE_STR);
+        (void) iovw_put_string_field(iovw, "PRIORITY=", STRINGIFY(LOG_CRIT));
+
+        /* Collect all process metadata from argv[] by making sure to skip the
+         * '--backtrace' option */
+        r = gather_pid_metadata_from_argv(iovw, &context, argc - 2, argv + 2);
+        if (r < 0)
+                goto finish;
+
+        /* Collect the rest of the process metadata retrieved from the runtime */
+        r = gather_pid_metadata(iovw, &context);
+        if (r < 0)
+                goto finish;
+
+        for (;;) {
+                r = journal_importer_process_data(&importer);
+                if (r < 0) {
+                        log_error_errno(r, "Failed to parse journal entry on stdin: %m");
+                        goto finish;
+                }
+                if (r == 1 ||                        /* complete entry */
+                    journal_importer_eof(&importer)) /* end of data */
+                        break;
+        }
+
+        if (journal_importer_eof(&importer)) {
+                log_warning("Did not receive a full journal entry on stdin, ignoring message sent by reporter");
+
+                message = strjoina("Process ", context.meta[META_ARGV_PID],
+                                  " (", context.meta[META_COMM], ")"
+                                  " of user ", context.meta[META_ARGV_UID],
+                                  " failed with ", context.meta[META_ARGV_SIGNAL]);
+
+                r = iovw_put_string_field(iovw, "MESSAGE=", message);
+                if (r < 0)
+                        goto finish;
+        } else {
+                /* The imported iovecs are not supposed to be freed by us so let's store
+                 * them at the end of the array so we can skip them while freeing the
+                 * rest. */
+                for (size_t i = 0; i < importer.iovw.count; i++) {
+                        struct iovec *iovec = importer.iovw.iovec + i;
+
+                        iovw_put(iovw, iovec->iov_base, iovec->iov_len);
+                }
+        }
+
+        r = sd_journal_sendv(iovw->iovec, iovw->count);
+        if (r < 0)
+                log_error_errno(r, "Failed to log backtrace: %m");
+
+ finish:
+        iovw->count -= importer.iovw.count;
+        iovw = iovw_free_free(iovw);
+        return r;
+}
+
+static int run(int argc, char *argv[]) {
+        int r;
+
+        /* First, log to a safe place, since we don't know what crashed and it might
+         * be journald which we'd rather not log to then. */
+
+        log_set_target(LOG_TARGET_KMSG);
+        log_open();
+
+        /* Make sure we never enter a loop */
+        (void) prctl(PR_SET_DUMPABLE, 0);
+
+        /* Ignore all parse errors */
+        (void) parse_config();
+
+        log_debug("Selected storage '%s'.", coredump_storage_to_string(arg_storage));
+        log_debug("Selected compression %s.", yes_no(arg_compress));
+
+        r = sd_listen_fds(false);
+        if (r < 0)
+                return log_error_errno(r, "Failed to determine the number of file descriptors: %m");
+
+        /* If we got an fd passed, we are running in coredumpd mode. Otherwise we
+         * are invoked from the kernel as coredump handler. */
+        if (r == 0) {
+                if (streq_ptr(argv[1], "--backtrace"))
+                        return process_backtrace(argc, argv);
+                else
+                        return process_kernel(argc, argv);
+        } else if (r == 1)
+                return process_socket(SD_LISTEN_FDS_START);
+
+        return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
+                               "Received unexpected number of file descriptors.");
+}
+
+DEFINE_MAIN_FUNCTION(run);