From: Jens Axboe <axboe@kernel.dk>
Date: Mon, 12 Oct 2020 17:53:29 +0000 (-0600)
Subject: io_uring: don't run task work on an exiting task
X-Git-Url: http://git.hungrycats.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=07463d7da99985d8254f6e5c66cd9843037a9bbd;p=linux

io_uring: don't run task work on an exiting task

commit 6200b0ae4ea28a4bfd8eb434e33e6201b7a6a282 upstream.

This isn't safe, and isn't needed either. We are guaranteed that any
work we queue is on a live task (and will be run), or it goes to
our backup io-wq threads if the task is exiting.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/fs/io_uring.c b/fs/io_uring.c
index d2bb2ae9551f..b706a4538a7f 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1762,6 +1762,12 @@ static int io_put_kbuf(struct io_kiocb *req)
 
 static inline bool io_run_task_work(void)
 {
+	/*
+	 * Not safe to run on exiting task, and the task_work handling will
+	 * not add work to such a task.
+	 */
+	if (unlikely(current->flags & PF_EXITING))
+		return false;
 	if (current->task_works) {
 		__set_current_state(TASK_RUNNING);
 		task_work_run();
@@ -7791,6 +7797,8 @@ static void io_uring_cancel_files(struct io_ring_ctx *ctx,
 			io_put_req(cancel_req);
 		}
 
+		/* cancellations _may_ trigger task work */
+		io_run_task_work();
 		schedule();
 		finish_wait(&ctx->inflight_wait, &wait);
 	}