From: Pavel Begunkov <asml.silence@gmail.com>
Date: Fri, 25 Oct 2019 12:31:31 +0300
Subject: io_uring: Fix race for sqes with userspace
Git-commit: 935d1e45908afb8853c497f2c2bbbb685dec51dc
Patch-mainline: 5.4-rc5
References: bnc#1151927 5.3.8

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>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 fs/io_uring.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2468,13 +2468,14 @@ static int io_ring_submit(struct io_ring
 		submit++;
 		io_submit_sqe(ctx, &s, statep, &link);
 	}
-	io_commit_sqring(ctx);
 
 	if (link)
 		io_queue_sqe(ctx, link, &link->submit);
 	if (statep)
 		io_submit_state_end(statep);
 
+	io_commit_sqring(ctx);
+
 	return submit;
 }