io_uring: Fix race for sqes with userspace

io_ring_submit() finalises with
1. io_commit_sqring(), which releases sqes to the userspace
2. Then calls to io_queue_link_head(), accessing released head's sqe

Reorder them.

Signed-off-by: Pavel Begunkov <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 949c82a..32f6598 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2795,13 +2795,14 @@ out:
                submit++;
                io_submit_sqe(ctx, &s, statep, &link);
        }
-       io_commit_sqring(ctx);
 
        if (link)
                io_queue_link_head(ctx, link, &link->submit, shadow_req);
        if (statep)
                io_submit_state_end(statep);
 
+       io_commit_sqring(ctx);
+
        return submit;
 }