This is a note to let you know that I've just added the patch titled
io_uring: fix ltout double free on completion race
to the 5.12-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-fix-ltout-double-free-on-completion-race.patch
and it can be found in the queue-5.12 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit d14225f0fd769f0ee7690c83ecfa35f667784566
Author: Pavel Begunkov <asml.silence@xxxxxxxxx>
Date: Fri May 14 12:02:50 2021 +0100
io_uring: fix ltout double free on completion race
[ Upstream commit 447c19f3b5074409c794b350b10306e1da1ef4ba ]
Always remove linked timeout on io_link_timeout_fn() from the master
request link list, otherwise we may get use-after-free when first
io_link_timeout_fn() puts linked timeout in the fail path, and then
will be found and put on master's free.
Cc: stable@xxxxxxxxxxxxxxx # 5.10+
Fixes: 90cd7e424969d ("io_uring: track link timeout's master explicitly")
Reported-and-tested-by: syzbot+5a864149dd970b546223@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
Link: https://lore.kernel.org/r/69c46bf6ce37fec4fdcd98f0882e18eb07ce693a.1620990121.git.asml.silence@xxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/fs/io_uring.c b/fs/io_uring.c
index dd8b3fac877c..359d1abb089c 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -6289,10 +6289,11 @@ static enum hrtimer_restart io_link_timeout_fn(struct hrtimer *timer)
* We don't expect the list to be empty, that will only happen if we
* race with the completion of the linked work.
*/
- if (prev && req_ref_inc_not_zero(prev))
+ if (prev) {
io_remove_next_linked(prev);
- else
- prev = NULL;
+ if (!req_ref_inc_not_zero(prev))
+ prev = NULL;
+ }
spin_unlock_irqrestore(&ctx->completion_lock, flags);
if (prev) {
