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Merge pull request #15920 from keszybz/userwork-proc-title

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Avoid log noise when setting proc titles and some doc updates
This commit is contained in:
Lennart Poettering
2020-05-26 18:29:06 +02:00
committed by GitHub
parent cf3317f63a e1a0423266
commit 7257f717c1
15 changed files with 126 additions and 106 deletions
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src/basic/process-util.c
+70 -60
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@@ -206,50 +206,12 @@ int get_process_cmdline(pid_t pid, size_t max_columns, ProcessCmdlineFlags flags
return 0;
}
int rename_process(const char name[]) {
static size_t mm_size = 0;
static char *mm = NULL;
bool truncated = false;
size_t l;
static int update_argv(const char name[], size_t l) {
static int can_do = -1;
/* 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 */
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;
}
/* 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. */
if (can_do == 0)
return 0;
can_do = false; /* We'll set it to true only if the whole process works */
/* Let's not bother with this if we don't have euid == 0. Strictly speaking we should check for the
* CAP_SYS_RESOURCE capability which is independent of the euid. In our own code the capability generally is
@@ -257,22 +219,29 @@ int rename_process(const char name[]) {
* PR_SET_MM_ARG_{START,END} fails with EPERM later on anyway. After all geteuid() is dead cheap to call, but
* mmap() is not. */
if (geteuid() != 0)
log_debug("Skipping PR_SET_MM, as we don't have privileges.");
else if (mm_size < l+1) {
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;
int r;
if (mm_size < l+1) {
size_t nn_size;
char *nn;
nn_size = PAGE_ALIGN(l+1);
nn = mmap(NULL, nn_size, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
if (nn == MAP_FAILED) {
log_debug_errno(errno, "mmap() failed: %m");
goto use_saved_argv;
}
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
@@ -284,15 +253,13 @@ int rename_process(const char name[]) {
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) {
log_debug_errno(errno, "PR_SET_MM_ARG_END hack failed, proceeding without: %m");
r = log_debug_errno(errno, "PR_SET_MM_ARG_END hack failed, proceeding without: %m");
(void) munmap(nn, nn_size);
goto use_saved_argv;
return r;
}
if (prctl(PR_SET_MM, PR_SET_MM_ARG_START, (unsigned long) nn, 0, 0) < 0) {
log_debug_errno(errno, "PR_SET_MM_ARG_START still failed, proceeding without: %m");
goto use_saved_argv;
}
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,
@@ -314,13 +281,56 @@ int rename_process(const char name[]) {
log_debug_errno(errno, "PR_SET_MM_ARG_END failed, proceeding without: %m");
}
use_saved_argv:
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;
}
/* 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) {
int i;
if (saved_argv[0]) {
size_t k;
@@ -330,7 +340,7 @@ use_saved_argv:
truncated = true;
}
for (i = 1; i < saved_argc; i++) {
for (int i = 1; i < saved_argc; i++) {
if (!saved_argv[i])
break;