diff options
Diffstat (limited to 'src/basic')
| -rw-r--r-- | src/basic/process-util.c | 102 | ||||
| -rw-r--r-- | src/basic/process-util.h | 2 |
2 files changed, 90 insertions, 14 deletions
diff --git a/src/basic/process-util.c b/src/basic/process-util.c index 1f4c2e4e43..d5e7edb589 100644 --- a/src/basic/process-util.c +++ b/src/basic/process-util.c @@ -27,6 +27,7 @@ #include <stdio.h> #include <stdlib.h> #include <string.h> +#include <sys/mman.h> #include <sys/personality.h> #include <sys/prctl.h> #include <sys/types.h> @@ -274,27 +275,100 @@ int get_process_cmdline(pid_t pid, size_t max_length, bool comm_fallback, char * return 0; } -void rename_process(const char name[8]) { - assert(name); +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 */ - /* 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 usually one of 10 (i.e. length - * of "/sbin/init"), to the third one one of 7 (i.e. length of - * "systemd"). If you pass a longer string it will be - * truncated */ + l = strlen(name); + /* First step, change the comm field. */ (void) prctl(PR_SET_NAME, name); + if (l > 15) /* Linux 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 (mm_size < l+1) { + size_t nn_size; + char *nn; + + /* Let's not bother with this if we don't have euid == 0. Strictly speaking if people do weird stuff + * with capabilities this could work even for euid != 0, but our own code generally doesn't do that, + * hence let's use this as quick bypass check, to avoid calling mmap() if PR_SET_MM_ARG_START 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_ARG_START, as we don't have privileges."); + goto use_saved_argv; + } + + 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; + } + + 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) { + log_debug_errno(errno, "PR_SET_MM_ARG_START failed, proceeding without: %m"); + (void) munmap(nn, nn_size); + goto use_saved_argv; + } + + /* 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 (program_invocation_name) - strncpy(program_invocation_name, name, strlen(program_invocation_name)); + if (mm) + (void) munmap(mm, mm_size); + + mm = nn; + mm_size = nn_size; + } else + strncpy(mm, name, mm_size); + +use_saved_argv: + /* 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]) - strncpy(saved_argv[0], name, strlen(saved_argv[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 (i = 1; i < saved_argc; i++) { if (!saved_argv[i]) @@ -303,6 +377,8 @@ void rename_process(const char name[8]) { memzero(saved_argv[i], strlen(saved_argv[i])); } } + + return !truncated; } int is_kernel_thread(pid_t pid) { diff --git a/src/basic/process-util.h b/src/basic/process-util.h index 89dfeb4d6a..d378901399 100644 --- a/src/basic/process-util.h +++ b/src/basic/process-util.h @@ -64,7 +64,7 @@ void sigkill_waitp(pid_t *pid); int kill_and_sigcont(pid_t pid, int sig); -void rename_process(const char name[8]); +int rename_process(const char name[]); int is_kernel_thread(pid_t pid); int getenv_for_pid(pid_t pid, const char *field, char **_value); |