From: Zbigniew Jędrzejewski-Szmek Date: Fri, 22 May 2020 07:00:49 +0000 (+0200) Subject: basic/process-util: create helper function X-Git-Tag: v246-rc1~287^2~4 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ad4f7f6747637288371263e550e7d3dc6630e6c0;p=thirdparty%2Fsystemd.git basic/process-util: create helper function No functional change. --- diff --git a/src/basic/process-util.c b/src/basic/process-util.c index 704d6682532..c96158ae5c5 100644 --- a/src/basic/process-util.c +++ b/src/basic/process-util.c @@ -206,68 +206,28 @@ 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; - - /* 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. */ - +static int update_argv(const char name[], size_t l) { /* 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 * present only for euid == 0, hence let's use this as quick bypass check, to avoid calling mmap() if * 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); @@ -284,15 +244,13 @@ 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 +272,55 @@ int rename_process(const char name[]) { log_debug_errno(errno, "PR_SET_MM_ARG_END failed, proceeding without: %m"); } -use_saved_argv: + 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 +330,7 @@ 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;