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authorMichal Koutný <mkoutny@suse.com>2023-10-09 15:58:11 +0200
committerTejun Heo <tj@kernel.org>2023-10-09 06:42:05 -1000
commit1ca0b605150501b7dc59f3016271da4eb3e96fce (patch)
tree7ad8733ea44511c6e188f27d622936224c1c3477 /kernel
parent94f6f0550c625fab1f373bb86a6669b45e9748b3 (diff)
cgroup: Remove duplicates in cgroup v1 tasks file
One PID may appear multiple times in a preloaded pidlist. (Possibly due to PID recycling but we have reports of the same task_struct appearing with different PIDs, thus possibly involving transfer of PID via de_thread().) Because v1 seq_file iterator uses PIDs as position, it leads to a message: > seq_file: buggy .next function kernfs_seq_next did not update position index Conservative and quick fix consists of removing duplicates from `tasks` file (as opposed to removing pidlists altogether). It doesn't affect correctness (it's sufficient to show a PID once), performance impact would be hidden by unconditional sorting of the pidlist already in place (asymptotically). Link: https://lore.kernel.org/r/20230823174804.23632-1-mkoutny@suse.com/ Suggested-by: Firo Yang <firo.yang@suse.com> Signed-off-by: Michal Koutný <mkoutny@suse.com> Signed-off-by: Tejun Heo <tj@kernel.org> Cc: stable@vger.kernel.org
Diffstat (limited to 'kernel')
-rw-r--r--kernel/cgroup/cgroup-v1.c5
1 files changed, 2 insertions, 3 deletions
diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c
index c487ffef6652..76db6c67e39a 100644
--- a/kernel/cgroup/cgroup-v1.c
+++ b/kernel/cgroup/cgroup-v1.c
@@ -360,10 +360,9 @@ static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
}
css_task_iter_end(&it);
length = n;
- /* now sort & (if procs) strip out duplicates */
+ /* now sort & strip out duplicates (tgids or recycled thread PIDs) */
sort(array, length, sizeof(pid_t), cmppid, NULL);
- if (type == CGROUP_FILE_PROCS)
- length = pidlist_uniq(array, length);
+ length = pidlist_uniq(array, length);
l = cgroup_pidlist_find_create(cgrp, type);
if (!l) {