diff options
| author | Wander Lairson Costa <wander@redhat.com> | 2024-06-20 09:56:17 -0300 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2024-07-01 13:01:44 +0200 |
| commit | b58652db66c910c2245f5bee7deca41c12d707b9 (patch) | |
| tree | 087eb25dd388e1ca3aa93159b5af76b921c84566 | |
| parent | 2feab2492deb2f14f9675dd6388e9e2bf669c27a (diff) | |
sched/deadline: Fix task_struct reference leak
During the execution of the following stress test with linux-rt:
stress-ng --cyclic 30 --timeout 30 --minimize --quiet
kmemleak frequently reported a memory leak concerning the task_struct:
unreferenced object 0xffff8881305b8000 (size 16136):
comm "stress-ng", pid 614, jiffies 4294883961 (age 286.412s)
object hex dump (first 32 bytes):
02 40 00 00 00 00 00 00 00 00 00 00 00 00 00 00 .@..............
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
debug hex dump (first 16 bytes):
53 09 00 00 00 00 00 00 00 00 00 00 00 00 00 00 S...............
backtrace:
[<00000000046b6790>] dup_task_struct+0x30/0x540
[<00000000c5ca0f0b>] copy_process+0x3d9/0x50e0
[<00000000ced59777>] kernel_clone+0xb0/0x770
[<00000000a50befdc>] __do_sys_clone+0xb6/0xf0
[<000000001dbf2008>] do_syscall_64+0x5d/0xf0
[<00000000552900ff>] entry_SYSCALL_64_after_hwframe+0x6e/0x76
The issue occurs in start_dl_timer(), which increments the task_struct
reference count and sets a timer. The timer callback, dl_task_timer,
is supposed to decrement the reference count upon expiration. However,
if enqueue_task_dl() is called before the timer expires and cancels it,
the reference count is not decremented, leading to the leak.
This patch fixes the reference leak by ensuring the task_struct
reference count is properly decremented when the timer is canceled.
Fixes: feff2e65efd8 ("sched/deadline: Unthrottle PI boosted threads while enqueuing")
Signed-off-by: Wander Lairson Costa <wander@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lore.kernel.org/r/20240620125618.11419-1-wander@redhat.com
| -rw-r--r-- | kernel/sched/deadline.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index c75d1307d86d..9bedd148f007 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -1804,8 +1804,13 @@ static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags) * The replenish timer needs to be canceled. No * problem if it fires concurrently: boosted threads * are ignored in dl_task_timer(). + * + * If the timer callback was running (hrtimer_try_to_cancel == -1), + * it will eventually call put_task_struct(). */ - hrtimer_try_to_cancel(&p->dl.dl_timer); + if (hrtimer_try_to_cancel(&p->dl.dl_timer) == 1 && + !dl_server(&p->dl)) + put_task_struct(p); p->dl.dl_throttled = 0; } } else if (!dl_prio(p->normal_prio)) { |