From: Pavel Begunkov asml.silence@gmail.com
commit a185f1db59f13de73aa470559030e90e50b34d93 upstream.
WARNING: CPU: 1 PID: 27907 at fs/io_uring.c:7147 io_sq_thread_park+0xb5/0xd0 fs/io_uring.c:7147 CPU: 1 PID: 27907 Comm: iou-sqp-27905 Not tainted 5.12.0-rc4-syzkaller #0 RIP: 0010:io_sq_thread_park+0xb5/0xd0 fs/io_uring.c:7147 Call Trace: io_ring_ctx_wait_and_kill+0x214/0x700 fs/io_uring.c:8619 io_uring_release+0x3e/0x50 fs/io_uring.c:8646 __fput+0x288/0x920 fs/file_table.c:280 task_work_run+0xdd/0x1a0 kernel/task_work.c:140 io_run_task_work fs/io_uring.c:2238 [inline] io_run_task_work fs/io_uring.c:2228 [inline] io_uring_try_cancel_requests+0x8ec/0xc60 fs/io_uring.c:8770 io_uring_cancel_sqpoll+0x1cf/0x290 fs/io_uring.c:8974 io_sqpoll_cancel_cb+0x87/0xb0 fs/io_uring.c:8907 io_run_task_work_head+0x58/0xb0 fs/io_uring.c:1961 io_sq_thread+0x3e2/0x18d0 fs/io_uring.c:6763 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
May happen that last ctx ref is killed in io_uring_cancel_sqpoll(), so fput callback (i.e. io_uring_release()) is enqueued through task_work, and run by same cancellation. As it's deeply nested we can't do parking or taking sqd->lock there, because its state is unclear. So avoid ctx ejection from sqd list from io_ring_ctx_wait_and_kill() and do it in a clear context in io_ring_exit_work().
Fixes: f6d54255f423 ("io_uring: halt SQO submission on ctx exit") Reported-by: syzbot+e3a3f84f5cecf61f0583@syzkaller.appspotmail.com Signed-off-by: Pavel Begunkov asml.silence@gmail.com Link: https://lore.kernel.org/r/e90df88b8ff2cabb14a7534601d35d62ab4cb8c7.161649670... Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/io_uring.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-)
--- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -8738,6 +8738,14 @@ static __poll_t io_uring_poll(struct fil if (!io_sqring_full(ctx)) mask |= EPOLLOUT | EPOLLWRNORM;
+ /* prevent SQPOLL from submitting new requests */ + if (ctx->sq_data) { + io_sq_thread_park(ctx->sq_data); + list_del_init(&ctx->sqd_list); + io_sqd_update_thread_idle(ctx->sq_data); + io_sq_thread_unpark(ctx->sq_data); + } + /* * Don't flush cqring overflow list here, just do a simple check. * Otherwise there could possible be ABBA deadlock: @@ -8816,14 +8824,6 @@ static void io_ring_ctx_wait_and_kill(st __io_cqring_overflow_flush(ctx, true, NULL, NULL); mutex_unlock(&ctx->uring_lock);
- /* prevent SQPOLL from submitting new requests */ - if (ctx->sq_data) { - io_sq_thread_park(ctx->sq_data); - list_del_init(&ctx->sqd_list); - io_sqd_update_thread_idle(ctx->sq_data); - io_sq_thread_unpark(ctx->sq_data); - } - io_kill_timeouts(ctx, NULL, NULL); io_poll_remove_all(ctx, NULL, NULL);