io_uring: fix io_prep_async_link locking
io_prep_async_link() may be called after arming a linked timeout,
automatically making it unsafe to traverse the linked list. Guard
with completion_lock if there was a linked timeout.
Cc: stable@vger.kernel.org # 5.9+
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/93f7c617e2b4f012a2a175b3dab6bc2f27cebc48.1627304436.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 5a0fd6b..c4d2b32 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1279,8 +1279,17 @@ static void io_prep_async_link(struct io_kiocb *req)
{
struct io_kiocb *cur;
- io_for_each_link(cur, req)
- io_prep_async_work(cur);
+ if (req->flags & REQ_F_LINK_TIMEOUT) {
+ struct io_ring_ctx *ctx = req->ctx;
+
+ spin_lock_irq(&ctx->completion_lock);
+ io_for_each_link(cur, req)
+ io_prep_async_work(cur);
+ spin_unlock_irq(&ctx->completion_lock);
+ } else {
+ io_for_each_link(cur, req)
+ io_prep_async_work(cur);
+ }
}
static void io_queue_async_work(struct io_kiocb *req)
