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process-util: update the end pointer of the process name on rename (#6492) 

We only updated the end pointer when allocating new memory, i.e. on the first
call to rename_process.
This commit is contained in:
Jouke Witteveen 2017-08-02 17:08:31 +02:00
parent ad6fc5bbae
commit 01f989c662
1 changed files with 15 additions and 11 deletions
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26
src/basic/process-util.c
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@ -312,19 +312,18 @@ int rename_process(const char 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. */
if (mm_size < l+1) {
/* 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) {
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) {
@ -351,9 +350,14 @@ int rename_process(const char name[]) {
mm = nn;
mm_size = nn_size;
} else
} 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");
}
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 */