6.12-stable review patch. If anyone has any objections, please let me know.
------------------
From: Pavel Begunkov <asml.silence@xxxxxxxxx>
commit dbd2ca9367eb19bc5e269b8c58b0b1514ada9156 upstream.
task work can be executed after the task has gone through io_uring
termination, whether it's the final task_work run or the fallback path.
In this case, task work will find ->io_wq being already killed and
null'ed, which is a problem if it then tries to forward the request to
io_queue_iowq(). Make io_queue_iowq() fail requests in this case.
Note that it also checks PF_KTHREAD, because the user can first close
a DEFER_TASKRUN ring and shortly after kill the task, in which case
->iowq check would race.
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 50c52250e2d74 ("block: implement async io_uring discard cmd")
Fixes: 773af69121ecc ("io_uring: always reissue from task_work context")
Reported-by: Will <willsroot@xxxxxxxxxxxxxx>
Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
Link: https://lore.kernel.org/r/63312b4a2c2bb67ad67b857d17a300e1d3b078e8.1734637909.git.asml.silence@xxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
io_uring/io_uring.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -515,7 +515,11 @@ static void io_queue_iowq(struct io_kioc
struct io_uring_task *tctx = req->task->io_uring;
BUG_ON(!tctx);
- BUG_ON(!tctx->io_wq);
+
+ if ((current->flags & PF_KTHREAD) || !tctx->io_wq) {
+ io_req_task_queue_fail(req, -ECANCELED);
+ return;
+ }
/* init ->work of the whole link before punting */
io_prep_async_link(req);
