Adding upstream version 255.4.upstream/255.4

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

1 files changed, 233 insertions, 0 deletions

diff --git a/src/basic/argv-util.c b/src/basic/argv-util.c
new file mode 100644
index 0000000..a2bcc44
--- /dev/null
+++ b/src/basic/argv-util.c
@@ -0,0 +1,233 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <sched.h>
+#include <sys/mman.h>
+#include <sys/prctl.h>
+#include <unistd.h>
+
+#include "argv-util.h"
+#include "capability-util.h"
+#include "errno-util.h"
+#include "missing_sched.h"
+#include "parse-util.h"
+#include "path-util.h"
+#include "process-util.h"
+#include "string-util.h"
+#include "strv.h"
+
+int saved_argc = 0;
+char **saved_argv = NULL;
+
+bool invoked_as(char *argv[], const char *token) {
+        if (!argv || isempty(argv[0]))
+                return false;
+
+        if (isempty(token))
+                return false;
+
+        return strstr(last_path_component(argv[0]), token);
+}
+
+bool invoked_by_systemd(void) {
+        int r;
+
+        /* If the process is directly executed by PID1 (e.g. ExecStart= or generator), systemd-importd,
+         * or systemd-homed, then $SYSTEMD_EXEC_PID= is set, and read the command line. */
+        const char *e = getenv("SYSTEMD_EXEC_PID");
+        if (!e)
+                return false;
+
+        if (streq(e, "*"))
+                /* For testing. */
+                return true;
+
+        pid_t p;
+        r = parse_pid(e, &p);
+        if (r < 0) {
+                /* We know that systemd sets the variable correctly. Something else must have set it. */
+                log_debug_errno(r, "Failed to parse \"SYSTEMD_EXEC_PID=%s\", ignoring: %m", e);
+                return false;
+        }
+
+        return getpid_cached() == p;
+}
+
+bool argv_looks_like_help(int argc, char **argv) {
+        char **l;
+
+        /* Scans the command line for indications the user asks for help. This is supposed to be called by
+         * tools that do not implement getopt() style command line parsing because they are not primarily
+         * user-facing. Detects four ways of asking for help:
+         *
+         * 1. Passing zero arguments
+         * 2. Passing "help" as first argument
+         * 3. Passing --help as any argument
+         * 4. Passing -h as any argument
+         */
+
+        if (argc <= 1)
+                return true;
+
+        if (streq_ptr(argv[1], "help"))
+                return true;
+
+        l = strv_skip(argv, 1);
+
+        return strv_contains(l, "--help") ||
+                strv_contains(l, "-h");
+}
+
+static int update_argv(const char name[], size_t l) {
+        static int can_do = -1;
+        int r;
+
+        assert(name);
+        assert(l < SIZE_MAX);
+
+        if (can_do == 0)
+                return 0;
+        can_do = false; /* We'll set it to true only if the whole process works */
+
+        /* Calling prctl() with PR_SET_MM_ARG_{START,END} requires CAP_SYS_RESOURCE so let's use this as quick bypass
+         * check, to avoid calling mmap() should PR_SET_MM_ARG_{START,END} fail with EPERM later on anyway. */
+        r = have_effective_cap(CAP_SYS_RESOURCE);
+        if (r < 0)
+                return log_debug_errno(r, "Failed to check if we have enough privileges: %m");
+        if (r == 0)
+                return log_debug_errno(SYNTHETIC_ERRNO(EPERM),
+                                       "Skipping PR_SET_MM, as we don't have privileges.");
+
+        static size_t mm_size = 0;
+        static char *mm = NULL;
+
+        if (mm_size < l+1) {
+                size_t nn_size;
+                char *nn;
+
+                nn_size = PAGE_ALIGN(l+1);
+                if (nn_size >= SIZE_MAX)
+                        return log_debug_errno(SYNTHETIC_ERRNO(EINVAL), "The requested argument is too long.");
+
+                nn = mmap(NULL, nn_size, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
+                if (nn == MAP_FAILED)
+                        return log_debug_errno(errno, "mmap() failed: %m");
+
+                strncpy(nn, name, nn_size);
+
+                /* Now, let's tell the kernel about this new memory */
+                if (prctl(PR_SET_MM, PR_SET_MM_ARG_START, (unsigned long) nn, 0, 0) < 0) {
+                        if (ERRNO_IS_PRIVILEGE(errno))
+                                return log_debug_errno(errno, "PR_SET_MM_ARG_START failed: %m");
+
+                        /* HACK: prctl() API is kind of dumb on this point.  The existing end address may already be
+                         * below the desired start address, in which case the kernel may have kicked this back due
+                         * to a range-check failure (see linux/kernel/sys.c:validate_prctl_map() to see this in
+                         * action).  The proper solution would be to have a prctl() API that could set both start+end
+                         * simultaneously, or at least let us query the existing address to anticipate this condition
+                         * and respond accordingly.  For now, we can only guess at the cause of this failure and try
+                         * a workaround--which will briefly expand the arg space to something potentially huge before
+                         * resizing it to what we want. */
+                        log_debug_errno(errno, "PR_SET_MM_ARG_START failed, attempting PR_SET_MM_ARG_END hack: %m");
+
+                        if (prctl(PR_SET_MM, PR_SET_MM_ARG_END, (unsigned long) nn + l + 1, 0, 0) < 0) {
+                                r = log_debug_errno(errno, "PR_SET_MM_ARG_END hack failed, proceeding without: %m");
+                                (void) munmap(nn, nn_size);
+                                return r;
+                        }
+
+                        if (prctl(PR_SET_MM, PR_SET_MM_ARG_START, (unsigned long) nn, 0, 0) < 0)
+                                return log_debug_errno(errno, "PR_SET_MM_ARG_START still failed, proceeding without: %m");
+                } else {
+                        /* And update the end pointer to the new end, too. If this fails, we don't really know what
+                         * to do, it's pretty unlikely that we can rollback, hence we'll just accept the failure,
+                         * and continue. */
+                        if (prctl(PR_SET_MM, PR_SET_MM_ARG_END, (unsigned long) nn + l + 1, 0, 0) < 0)
+                                log_debug_errno(errno, "PR_SET_MM_ARG_END failed, proceeding without: %m");
+                }
+
+                if (mm)
+                        (void) munmap(mm, mm_size);
+
+                mm = nn;
+                mm_size = nn_size;
+        } else {
+                strncpy(mm, name, mm_size);
+
+                /* Update the end pointer, continuing regardless of any failure. */
+                if (prctl(PR_SET_MM, PR_SET_MM_ARG_END, (unsigned long) mm + l + 1, 0, 0) < 0)
+                        log_debug_errno(errno, "PR_SET_MM_ARG_END failed, proceeding without: %m");
+        }
+
+        can_do = true;
+        return 0;
+}
+
+int rename_process(const char name[]) {
+        bool truncated = false;
+
+        /* This is a like a poor man's setproctitle(). It changes the comm field, argv[0], and also the glibc's
+         * internally used name of the process. For the first one a limit of 16 chars applies; to the second one in
+         * many cases one of 10 (i.e. length of "/sbin/init") — however if we have CAP_SYS_RESOURCES it is unbounded;
+         * to the third one 7 (i.e. the length of "systemd". If you pass a longer string it will likely be
+         * truncated.
+         *
+         * Returns 0 if a name was set but truncated, > 0 if it was set but not truncated. */
+
+        if (isempty(name))
+                return -EINVAL; /* let's not confuse users unnecessarily with an empty name */
+
+        if (!is_main_thread())
+                return -EPERM; /* Let's not allow setting the process name from other threads than the main one, as we
+                                * cache things without locking, and we make assumptions that PR_SET_NAME sets the
+                                * process name that isn't correct on any other threads */
+
+        size_t l = strlen(name);
+
+        /* First step, change the comm field. The main thread's comm is identical to the process comm. This means we
+         * can use PR_SET_NAME, which sets the thread name for the calling thread. */
+        if (prctl(PR_SET_NAME, name) < 0)
+                log_debug_errno(errno, "PR_SET_NAME failed: %m");
+        if (l >= TASK_COMM_LEN) /* Linux userspace process names can be 15 chars at max */
+                truncated = true;
+
+        /* Second step, change glibc's ID of the process name. */
+        if (program_invocation_name) {
+                size_t k;
+
+                k = strlen(program_invocation_name);
+                strncpy(program_invocation_name, name, k);
+                if (l > k)
+                        truncated = true;
+
+                /* Also update the short name. */
+                char *p = strrchr(program_invocation_name, '/');
+                program_invocation_short_name = p ? p + 1 : program_invocation_name;
+        }
+
+        /* Third step, completely replace the argv[] array the kernel maintains for us. This requires privileges, but
+         * has the advantage that the argv[] array is exactly what we want it to be, and not filled up with zeros at
+         * the end. This is the best option for changing /proc/self/cmdline. */
+        (void) update_argv(name, l);
+
+        /* Fourth step: in all cases we'll also update the original argv[], so that our own code gets it right too if
+         * it still looks here */
+        if (saved_argc > 0) {
+                if (saved_argv[0]) {
+                        size_t k;
+
+                        k = strlen(saved_argv[0]);
+                        strncpy(saved_argv[0], name, k);
+                        if (l > k)
+                                truncated = true;
+                }
+
+                for (int i = 1; i < saved_argc; i++) {
+                        if (!saved_argv[i])
+                                break;
+
+                        memzero(saved_argv[i], strlen(saved_argv[i]));
+                }
+        }
+
+        return !truncated;
+}