5.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: Pavel Begunkov <asml.silence@xxxxxxxxx>
commit f8b632e89a101dae349a7b212c1771d7925f441b upstream.
io_uring_cancel_generic() should retry if any state changes like a
request is completed, however in case of a task exit it only goes for
another loop and avoids schedule() if any tracked (i.e. REQ_F_INFLIGHT)
request got completed.
Let's assume we have a non-tracked request executing in iowq and a
tracked request linked to it. Let's also assume
io_uring_cancel_generic() fails to find and cancel the request, i.e.
via io_run_local_work(), which may happen as io-wq has gaps.
Next, the request logically completes, io-wq still hold a ref but queues
it for completion via tw, which happens in
io_uring_try_cancel_requests(). After, right before prepare_to_wait()
io-wq puts the request, grabs the linked one and tries executes it, e.g.
arms polling. Finally the cancellation loop calls prepare_to_wait(),
there are no tw to run, no tracked request was completed, so the
tctx_inflight() check passes and the task is put to indefinite sleep.
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 3f48cf18f886c ("io_uring: unify files and task cancel")
Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
Link: https://lore.kernel.org/r/acac7311f4e02ce3c43293f8f1fda9c705d158f1.1721819383.git.asml.silence@xxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
io_uring/io_uring.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -9856,8 +9856,11 @@ static void io_uring_cancel_generic(bool
atomic_inc(&tctx->in_idle);
do {
io_uring_drop_tctx_refs(current);
+ if (!tctx_inflight(tctx, !cancel_all))
+ break;
+
/* read completions before cancelations */
- inflight = tctx_inflight(tctx, !cancel_all);
+ inflight = tctx_inflight(tctx, false);
if (!inflight)
break;
