Adding upstream version 255.4.upstream/255.4

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

1 files changed, 379 insertions, 0 deletions

diff --git a/src/basic/xattr-util.c b/src/basic/xattr-util.c
new file mode 100644
index 0000000..d2daf87
--- /dev/null
+++ b/src/basic/xattr-util.c
@@ -0,0 +1,379 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <sys/time.h>
+#include <sys/xattr.h>
+
+#include "alloc-util.h"
+#include "errno-util.h"
+#include "fd-util.h"
+#include "macro.h"
+#include "missing_syscall.h"
+#include "parse-util.h"
+#include "sparse-endian.h"
+#include "stat-util.h"
+#include "stdio-util.h"
+#include "string-util.h"
+#include "time-util.h"
+#include "xattr-util.h"
+
+int getxattr_at_malloc(
+                int fd,
+                const char *path,
+                const char *name,
+                int flags,
+                char **ret) {
+
+        _cleanup_close_ int opened_fd = -EBADF;
+        unsigned n_attempts = 7;
+        bool by_procfs = false;
+        size_t l = 100;
+
+        assert(fd >= 0 || fd == AT_FDCWD);
+        assert(name);
+        assert((flags & ~(AT_SYMLINK_FOLLOW|AT_EMPTY_PATH)) == 0);
+        assert(ret);
+
+        /* So, this is single function that does what getxattr()/lgetxattr()/fgetxattr() does, but in one go,
+         * and with additional bells and whistles. Specifically:
+         *
+         * 1. This works on O_PATH fds (which fgetxattr() does not)
+         * 2. Provides full openat()-style semantics, i.e. by-fd, by-path and combination thereof
+         * 3. As extension to openat()-style semantics implies AT_EMPTY_PATH if path is NULL.
+         * 4. Does a malloc() loop, automatically sizing the allocation
+         * 5. NUL-terminates the returned buffer (for safety)
+         */
+
+        if (!path) /* If path is NULL, imply AT_EMPTY_PATH. – But if it's "", don't — for safety reasons. */
+                flags |= AT_EMPTY_PATH;
+
+        if (isempty(path)) {
+                if (!FLAGS_SET(flags, AT_EMPTY_PATH))
+                        return -EINVAL;
+
+                if (fd == AT_FDCWD) /* Both unspecified? Then operate on current working directory */
+                        path = ".";
+                else
+                        path = NULL;
+
+        } else if (fd != AT_FDCWD) {
+
+                /* If both have been specified, then we go via O_PATH */
+                opened_fd = openat(fd, path, O_PATH|O_CLOEXEC|(FLAGS_SET(flags, AT_SYMLINK_FOLLOW) ? 0 : O_NOFOLLOW));
+                if (opened_fd < 0)
+                        return -errno;
+
+                fd = opened_fd;
+                path = NULL;
+                by_procfs = true; /* fgetxattr() is not going to work, go via /proc/ link right-away */
+        }
+
+        for (;;) {
+                _cleanup_free_ char *v = NULL;
+                ssize_t n;
+
+                if (n_attempts == 0) /* If someone is racing against us, give up eventually */
+                        return -EBUSY;
+                n_attempts--;
+
+                v = new0(char, l+1);
+                if (!v)
+                        return -ENOMEM;
+
+                l = MALLOC_ELEMENTSOF(v) - 1;
+
+                if (path)
+                        n = FLAGS_SET(flags, AT_SYMLINK_FOLLOW) ? getxattr(path, name, v, l) : lgetxattr(path, name, v, l);
+                else
+                        n = by_procfs ? getxattr(FORMAT_PROC_FD_PATH(fd), name, v, l) : fgetxattr(fd, name, v, l);
+                if (n < 0) {
+                        if (errno == EBADF) {
+                                if (by_procfs || path)
+                                        return -EBADF;
+
+                                by_procfs = true; /* Might be an O_PATH fd, try again via /proc/ link */
+                                continue;
+                        }
+
+                        if (errno != ERANGE)
+                                return -errno;
+                } else {
+                        v[n] = 0; /* NUL terminate */
+                        *ret = TAKE_PTR(v);
+                        return (int) n;
+                }
+
+                if (path)
+                        n = FLAGS_SET(flags, AT_SYMLINK_FOLLOW) ? getxattr(path, name, NULL, 0) : lgetxattr(path, name, NULL, 0);
+                else
+                        n = by_procfs ? getxattr(FORMAT_PROC_FD_PATH(fd), name, NULL, 0) : fgetxattr(fd, name, NULL, 0);
+                if (n < 0)
+                        return -errno;
+                if (n > INT_MAX) /* We couldn't return this as 'int' anymore */
+                        return -E2BIG;
+
+                l = (size_t) n;
+        }
+}
+
+int getxattr_at_bool(int fd, const char *path, const char *name, int flags) {
+        _cleanup_free_ char *v = NULL;
+        int r;
+
+        r = getxattr_at_malloc(fd, path, name, flags, &v);
+        if (r < 0)
+                return r;
+
+        if (memchr(v, 0, r)) /* Refuse embedded NUL byte */
+                return -EINVAL;
+
+        return parse_boolean(v);
+}
+
+static int parse_crtime(le64_t le, usec_t *usec) {
+        uint64_t u;
+
+        assert(usec);
+
+        u = le64toh(le);
+        if (IN_SET(u, 0, UINT64_MAX))
+                return -EIO;
+
+        *usec = (usec_t) u;
+        return 0;
+}
+
+int fd_getcrtime_at(
+                int fd,
+                const char *path,
+                int flags,
+                usec_t *ret) {
+
+        _cleanup_free_ le64_t *le = NULL;
+        STRUCT_STATX_DEFINE(sx);
+        usec_t a, b;
+        int r;
+
+        assert(fd >= 0 || fd == AT_FDCWD);
+        assert((flags & ~(AT_SYMLINK_FOLLOW|AT_EMPTY_PATH)) == 0);
+        assert(ret);
+
+        if (!path)
+                flags |= AT_EMPTY_PATH;
+
+        /* So here's the deal: the creation/birth time (crtime/btime) of a file is a relatively newly supported concept
+         * on Linux (or more strictly speaking: a concept that only recently got supported in the API, it was
+         * implemented on various file systems on the lower level since a while, but never was accessible). However, we
+         * needed a concept like that for vacuuming algorithms and such, hence we emulated it via a user xattr for a
+         * long time. Starting with Linux 4.11 there's statx() which exposes the timestamp to userspace for the first
+         * time, where it is available. This function will read it, but it tries to keep some compatibility with older
+         * systems: we try to read both the crtime/btime and the xattr, and then use whatever is older. After all the
+         * concept is useful for determining how "old" a file really is, and hence using the older of the two makes
+         * most sense. */
+
+        if (statx(fd, strempty(path),
+                  (flags & ~AT_SYMLINK_FOLLOW)|(FLAGS_SET(flags, AT_SYMLINK_FOLLOW) ? 0 : AT_SYMLINK_NOFOLLOW)|AT_STATX_DONT_SYNC,
+                  STATX_BTIME,
+                  &sx) >= 0 &&
+            (sx.stx_mask & STATX_BTIME) &&
+            sx.stx_btime.tv_sec != 0)
+                a = (usec_t) sx.stx_btime.tv_sec * USEC_PER_SEC +
+                        (usec_t) sx.stx_btime.tv_nsec / NSEC_PER_USEC;
+        else
+                a = USEC_INFINITY;
+
+        r = getxattr_at_malloc(fd, path, "user.crtime_usec", flags, (char**) &le);
+        if (r >= 0) {
+                if (r != sizeof(*le))
+                        r = -EIO;
+                else
+                        r = parse_crtime(*le, &b);
+        }
+        if (r < 0) {
+                if (a != USEC_INFINITY) {
+                        *ret = a;
+                        return 0;
+                }
+
+                return r;
+        }
+
+        if (a != USEC_INFINITY)
+                *ret = MIN(a, b);
+        else
+                *ret = b;
+
+        return 0;
+}
+
+int fd_setcrtime(int fd, usec_t usec) {
+        le64_t le;
+
+        assert(fd >= 0);
+
+        if (!timestamp_is_set(usec))
+                usec = now(CLOCK_REALTIME);
+
+        le = htole64((uint64_t) usec);
+        return RET_NERRNO(fsetxattr(fd, "user.crtime_usec", &le, sizeof(le), 0));
+}
+
+int listxattr_at_malloc(
+                int fd,
+                const char *path,
+                int flags,
+                char **ret) {
+
+        _cleanup_close_ int opened_fd = -EBADF;
+        bool by_procfs = false;
+        unsigned n_attempts = 7;
+        size_t l = 100;
+
+        assert(fd >= 0 || fd == AT_FDCWD);
+        assert((flags & ~(AT_SYMLINK_FOLLOW|AT_EMPTY_PATH)) == 0);
+        assert(ret);
+
+        /* This is to listxattr()/llistattr()/flistattr() what getxattr_at_malloc() is to getxattr()/… */
+
+        if (!path) /* If path is NULL, imply AT_EMPTY_PATH. – But if it's "", don't. */
+                flags |= AT_EMPTY_PATH;
+
+        if (isempty(path)) {
+                if (!FLAGS_SET(flags, AT_EMPTY_PATH))
+                        return -EINVAL;
+
+                if (fd == AT_FDCWD) /* Both unspecified? Then operate on current working directory */
+                        path = ".";
+                else
+                        path = NULL;
+
+        } else if (fd != AT_FDCWD) {
+                /* If both have been specified, then we go via O_PATH */
+                opened_fd = openat(fd, path, O_PATH|O_CLOEXEC|(FLAGS_SET(flags, AT_SYMLINK_FOLLOW) ? 0 : O_NOFOLLOW));
+                if (opened_fd < 0)
+                        return -errno;
+
+                fd = opened_fd;
+                path = NULL;
+                by_procfs = true;
+        }
+
+        for (;;) {
+                _cleanup_free_ char *v = NULL;
+                ssize_t n;
+
+                if (n_attempts == 0) /* If someone is racing against us, give up eventually */
+                        return -EBUSY;
+                n_attempts--;
+
+                v = new(char, l+1);
+                if (!v)
+                        return -ENOMEM;
+
+                l = MALLOC_ELEMENTSOF(v) - 1;
+
+                if (path)
+                        n = FLAGS_SET(flags, AT_SYMLINK_FOLLOW) ? listxattr(path, v, l) : llistxattr(path, v, l);
+                else
+                        n = by_procfs ? listxattr(FORMAT_PROC_FD_PATH(fd), v, l) : flistxattr(fd, v, l);
+                if (n < 0) {
+                        if (errno == EBADF) {
+                                if (by_procfs || path)
+                                        return -EBADF;
+
+                                by_procfs = true; /* Might be an O_PATH fd, try again via /proc/ link */
+                                continue;
+                        }
+
+                        if (errno != ERANGE)
+                                return -errno;
+                } else {
+                        v[n] = 0; /* NUL terminate */
+                        *ret = TAKE_PTR(v);
+                        return (int) n;
+                }
+
+                if (path)
+                        n = FLAGS_SET(flags, AT_SYMLINK_FOLLOW) ? listxattr(path, NULL, 0) : llistxattr(path, NULL, 0);
+                else
+                        n = by_procfs ? listxattr(FORMAT_PROC_FD_PATH(fd), NULL, 0) : flistxattr(fd, NULL, 0);
+                if (n < 0)
+                        return -errno;
+                if (n > INT_MAX) /* We couldn't return this as 'int' anymore */
+                        return -E2BIG;
+
+                l = (size_t) n;
+        }
+}
+
+int xsetxattr(int fd,
+              const char *path,
+              const char *name,
+              const char *value,
+              size_t size,
+              int flags) {
+
+        _cleanup_close_ int opened_fd = -EBADF;
+        bool by_procfs = false;
+        int r;
+
+        assert(fd >= 0 || fd == AT_FDCWD);
+        assert(name);
+        assert(value);
+        assert((flags & ~(AT_SYMLINK_FOLLOW|AT_EMPTY_PATH)) == 0);
+
+        /* So, this is a single function that does what setxattr()/lsetxattr()/fsetxattr() do, but in one go,
+         * and with additional bells and whistles. Specifically:
+         *
+         * 1. This works on O_PATH fds (which fsetxattr() does not)
+         * 2. Provides full openat()-style semantics, i.e. by-fd, by-path and combination thereof
+         * 3. As extension to openat()-style semantics implies AT_EMPTY_PATH if path is NULL.
+         */
+
+        if (!path) /* If path is NULL, imply AT_EMPTY_PATH. – But if it's "", don't — for safety reasons. */
+                flags |= AT_EMPTY_PATH;
+
+        if (size == SIZE_MAX)
+                size = strlen(value);
+
+        if (isempty(path)) {
+                if (!FLAGS_SET(flags, AT_EMPTY_PATH))
+                        return -EINVAL;
+
+                if (fd == AT_FDCWD) /* Both unspecified? Then operate on current working directory */
+                        path = ".";
+                else {
+                        r = fd_is_opath(fd);
+                        if (r < 0)
+                                return r;
+
+                        by_procfs = r;
+                        path = NULL;
+                }
+
+        } else if (fd != AT_FDCWD) {
+
+                /* If both have been specified, then we go via O_PATH */
+                opened_fd = openat(fd, path, O_PATH|O_CLOEXEC|(FLAGS_SET(flags, AT_SYMLINK_FOLLOW) ? 0 : O_NOFOLLOW));
+                if (opened_fd < 0)
+                        return -errno;
+
+                fd = opened_fd;
+                path = NULL;
+                by_procfs = true; /* fsetxattr() is not going to work, go via /proc/ link right-away */
+        }
+
+        if (path)
+                r = FLAGS_SET(flags, AT_SYMLINK_FOLLOW) ? setxattr(path, name, value, size, 0)
+                                                        : lsetxattr(path, name, value, size, 0);
+        else
+                r = by_procfs ? setxattr(FORMAT_PROC_FD_PATH(fd), name, value, size, 0)
+                              : fsetxattr(fd, name, value, size, 0);
+        if (r < 0)
+                return -errno;
+
+        return 0;
+}