Patch "io_uring/cancel: re-grab ctx mutex after finishing wait" has been added to the 6.1-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    io_uring/cancel: re-grab ctx mutex after finishing wait

to the 6.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     io_uring-cancel-re-grab-ctx-mutex-after-finishing-wa.patch
and it can be found in the queue-6.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 1b2af895065c732348964d5c6dac2f1ca08f4891
Author: Jens Axboe <axboe@xxxxxxxxx>
Date:   Wed Dec 21 07:11:33 2022 -0700

    io_uring/cancel: re-grab ctx mutex after finishing wait
    
    [ Upstream commit 23fffb2f09ce1145cbd751801d45ba74acaa6542 ]
    
    If we have a signal pending during cancelations, it'll cause the
    task_work run to return an error. Since we didn't run task_work, the
    current task is left in TASK_INTERRUPTIBLE state when we need to
    re-grab the ctx mutex, and the kernel will rightfully complain about
    that.
    
    Move the lock grabbing for the error cases outside the loop to avoid
    that issue.
    
    Reported-by: syzbot+7df055631cd1be4586fd@xxxxxxxxxxxxxxxxxxxxxxxxx
    Link: https://lore.kernel.org/io-uring/0000000000003a14a905f05050b0@xxxxxxxxxx/
    Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/io_uring/cancel.c b/io_uring/cancel.c
index 2291a53cdabd..b4f5dfacc0c3 100644
--- a/io_uring/cancel.c
+++ b/io_uring/cancel.c
@@ -288,24 +288,23 @@ int io_sync_cancel(struct io_ring_ctx *ctx, void __user *arg)
 
 		ret = __io_sync_cancel(current->io_uring, &cd, sc.fd);
 
+		mutex_unlock(&ctx->uring_lock);
 		if (ret != -EALREADY)
 			break;
 
-		mutex_unlock(&ctx->uring_lock);
 		ret = io_run_task_work_sig(ctx);
-		if (ret < 0) {
-			mutex_lock(&ctx->uring_lock);
+		if (ret < 0)
 			break;
-		}
 		ret = schedule_hrtimeout(&timeout, HRTIMER_MODE_ABS);
-		mutex_lock(&ctx->uring_lock);
 		if (!ret) {
 			ret = -ETIME;
 			break;
 		}
+		mutex_lock(&ctx->uring_lock);
 	} while (1);
 
 	finish_wait(&ctx->cq_wait, &wait);
+	mutex_lock(&ctx->uring_lock);
 
 	if (ret == -ENOENT || ret > 0)
 		ret = 0;