On 12/5/21 11:43 PM, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: 944207047ca4 Merge tag 'usb-5.16-rc4' of git://git.kernel... > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=13ebd129b00000 > kernel config: https://syzkaller.appspot.com/x/.config?x=171728a464c05f2b > dashboard link: https://syzkaller.appspot.com/bug?extid=b60c982cb0efc5e05a47 > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 > > Unfortunately, I don't have any reproducer for this issue yet. > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+b60c982cb0efc5e05a47@xxxxxxxxxxxxxxxxxxxxxxxxx > > ================================================================== > BUG: KASAN: use-after-free in instrument_atomic_write include/linux/instrumented.h:86 [inline] > BUG: KASAN: use-after-free in clear_bit_unlock include/asm-generic/bitops/instrumented-lock.h:25 [inline] > BUG: KASAN: use-after-free in io_queue_worker_create+0x453/0x4e0 fs/io-wq.c:363 > Write of size 8 at addr ffff888023e068d8 by task kworker/3:4/13798 Looks like a spurious clear that can race with the task_work already ran and the worker got dropped. Both handlers do clear it, so I think we just need: diff --git a/fs/io-wq.c b/fs/io-wq.c index 50cf9f92da36..35da9d90df76 100644 --- a/fs/io-wq.c +++ b/fs/io-wq.c @@ -359,10 +359,8 @@ static bool io_queue_worker_create(struct io_worker *worker, init_task_work(&worker->create_work, func); worker->create_index = acct->index; - if (!task_work_add(wq->task, &worker->create_work, TWA_SIGNAL)) { - clear_bit_unlock(0, &worker->create_state); + if (!task_work_add(wq->task, &worker->create_work, TWA_SIGNAL)) return true; - } clear_bit_unlock(0, &worker->create_state); fail_release: io_worker_release(worker); -- Jens Axboe
