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argv-util: do proper permission check while when changing process name

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Process renaming happens very seldomly so we are able to afford proper
permission check, i.e. actually check for CAP_SYS_RESOURCE capability
instead of euid.
This commit is contained in:
Michal Sekletar 2022-12-19 17:29:40 +01:00
parent 5ac1e0eff3
commit 03ee26168f
1 changed files with 4 additions and 6 deletions
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10
src/basic/argv-util.c
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@ -6,6 +6,7 @@
#include <unistd.h>
#include "argv-util.h"
#include "capability-util.h"
#include "errno-util.h"
#include "missing_sched.h"
#include "parse-util.h"
@ -83,12 +84,9 @@ static int update_argv(const char name[], size_t l) {
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
* 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)
/* 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. */
if (!have_effective_cap(CAP_SYS_RESOURCE))
return log_debug_errno(SYNTHETIC_ERRNO(EPERM),
"Skipping PR_SET_MM, as we don't have privileges.");