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cgroup-util: Don't try to open pidfd for pids from cgroup.threads

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Opening pidfds for non thread group leaders only works from 6.9 onwards with PIDFD_THREAD. On
older kernels or without PIDFD_THREAD pidfd_open() fails with EINVAL. Since we might read non
thread group leader IDs from cgroup.threads, we introduce and set CGROUP_NO_PIDFD to avoid
trying open pidfd's for them and instead use the pid as is.
This commit is contained in:
Daan De Meyer
2024-05-29 22:03:38 +02:00
parent 9ac8450e7f
commit 8783355fd9
2 changed files with 12 additions and 2 deletions
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13
src/basic/cgroup-util.c
View File

@@ -149,6 +149,11 @@ int cg_read_pidref(FILE *f, PidRef *ret, CGroupFlags flags) {
if (pid == 0)
return -EREMOTE;
if (FLAGS_SET(flags, CGROUP_NO_PIDFD)) {
*ret = PIDREF_MAKE_FROM_PID(pid);
return 1;
}
r = pidref_set_pid(ret, pid);
if (r >= 0)
return 1;
@@ -352,7 +357,7 @@ static int cg_kill_items(
for (;;) {
_cleanup_(pidref_done) PidRef pidref = PIDREF_NULL;
r = cg_read_pidref(f, &pidref, /* flags = */ 0);
r = cg_read_pidref(f, &pidref, flags);
if (r < 0)
return RET_GATHER(ret, log_debug_errno(r, "Failed to read pidref from cgroup '%s': %m", path));
if (r == 0)
@@ -425,7 +430,11 @@ int cg_kill(
if (r == 0)
return ret;
r = cg_kill_items(path, sig, flags, s, log_kill, userdata, "cgroup.threads");
/* Opening pidfds for non thread group leaders only works from 6.9 onwards with PIDFD_THREAD. On
* older kernels or without PIDFD_THREAD pidfd_open() fails with EINVAL. Since we might read non
* thread group leader IDs from cgroup.threads, we set CGROUP_NO_PIDFD to avoid trying open pidfd's
* for them and instead use the regular pid. */
r = cg_kill_items(path, sig, flags|CGROUP_NO_PIDFD, s, log_kill, userdata, "cgroup.threads");
if (r < 0)
return log_debug_errno(r, "Failed to kill processes in cgroup '%s' item cgroup.threads: %m", path);

1
src/basic/cgroup-util.h
View File

@@ -188,6 +188,7 @@ typedef enum CGroupFlags {
CGROUP_IGNORE_SELF = 1 << 1,
CGROUP_REMOVE = 1 << 2,
CGROUP_DONT_SKIP_UNMAPPED = 1 << 3,
CGROUP_NO_PIDFD = 1 << 4,
} CGroupFlags;
int cg_enumerate_processes(const char *controller, const char *path, FILE **ret);