6.12-stable review patch. If anyone has any objections, please let me know.
------------------
From: Pavel Begunkov <asml.silence@xxxxxxxxx>
commit 4b7cfa8b6c28a9fa22b86894166a1a34f6d630ba upstream.
Syzkeller reports:
BUG: KASAN: slab-use-after-free in thread_group_cputime+0x409/0x700 kernel/sched/cputime.c:341
Read of size 8 at addr ffff88803578c510 by task syz.2.3223/27552
Call Trace:
<TASK>
...
kasan_report+0x143/0x180 mm/kasan/report.c:602
thread_group_cputime+0x409/0x700 kernel/sched/cputime.c:341
thread_group_cputime_adjusted+0xa6/0x340 kernel/sched/cputime.c:639
getrusage+0x1000/0x1340 kernel/sys.c:1863
io_uring_show_fdinfo+0xdfe/0x1770 io_uring/fdinfo.c:197
seq_show+0x608/0x770 fs/proc/fd.c:68
...
That's due to sqd->task not being cleared properly in cases where
SQPOLL task tctx setup fails, which can essentially only happen with
fault injection to insert allocation errors.
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 1251d2025c3e1 ("io_uring/sqpoll: early exit thread if task_context wasn't allocated")
Reported-by: syzbot+3d92cfcfa84070b0a470@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
Link: https://lore.kernel.org/r/efc7ec7010784463b2e7466d7b5c02c2cb381635.1736519461.git.asml.silence@xxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
io_uring/sqpoll.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
--- a/io_uring/sqpoll.c
+++ b/io_uring/sqpoll.c
@@ -275,8 +275,12 @@ static int io_sq_thread(void *data)
DEFINE_WAIT(wait);
/* offload context creation failed, just exit */
- if (!current->io_uring)
+ if (!current->io_uring) {
+ mutex_lock(&sqd->lock);
+ sqd->thread = NULL;
+ mutex_unlock(&sqd->lock);
goto err_out;
+ }
snprintf(buf, sizeof(buf), "iou-sqp-%d", sqd->task_pid);
set_task_comm(current, buf);
