The patch below does not apply to the 5.11-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 34343786ecc5ff493ca4d1f873b4386759ba52ee Mon Sep 17 00:00:00 2001
From: Pavel Begunkov asml.silence@gmail.com Date: Wed, 10 Feb 2021 11:45:42 +0000 Subject: [PATCH] io_uring: unpark SQPOLL thread for cancelation
We park SQPOLL task before going into io_uring_cancel_files(), so the task won't run task_works including those that might be important for the cancellation passes. In this case it's io_poll_remove_one(), which frees requests via io_put_req_deferred().
Unpark it for while waiting, it's ok as we disable submissions beforehand, so no new requests will be generated.
INFO: task syz-executor893:8493 blocked for more than 143 seconds. Call Trace: context_switch kernel/sched/core.c:4327 [inline] __schedule+0x90c/0x21a0 kernel/sched/core.c:5078 schedule+0xcf/0x270 kernel/sched/core.c:5157 io_uring_cancel_files fs/io_uring.c:8912 [inline] io_uring_cancel_task_requests+0xe70/0x11a0 fs/io_uring.c:8979 __io_uring_files_cancel+0x110/0x1b0 fs/io_uring.c:9067 io_uring_files_cancel include/linux/io_uring.h:51 [inline] do_exit+0x2fe/0x2ae0 kernel/exit.c:780 do_group_exit+0x125/0x310 kernel/exit.c:922 __do_sys_exit_group kernel/exit.c:933 [inline] __se_sys_exit_group kernel/exit.c:931 [inline] __x64_sys_exit_group+0x3a/0x50 kernel/exit.c:931 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xa9
Cc: stable@vger.kernel.org # 5.5+ Reported-by: syzbot+695b03d82fa8e4901b06@syzkaller.appspotmail.com Signed-off-by: Pavel Begunkov asml.silence@gmail.com Signed-off-by: Jens Axboe axboe@kernel.dk
diff --git a/fs/io_uring.c b/fs/io_uring.c index 7a1e4ecf5f94..9ed79509f389 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -9047,11 +9047,16 @@ static void io_uring_cancel_files(struct io_ring_ctx *ctx, break;
io_uring_try_cancel_requests(ctx, task, files); + + if (ctx->sq_data) + io_sq_thread_unpark(ctx->sq_data); prepare_to_wait(&task->io_uring->wait, &wait, TASK_UNINTERRUPTIBLE); if (inflight == io_uring_count_inflight(ctx, task, files)) schedule(); finish_wait(&task->io_uring->wait, &wait); + if (ctx->sq_data) + io_sq_thread_park(ctx->sq_data); } }