commit 935d1e45908afb8853c497f2c2bbbb685dec51dc
author Pavel Begunkov <asml.silence@gmail.com> Fri Oct 25 12:31:31 2019 +0300
committer Jens Axboe <axboe@kernel.dk> Fri Oct 25 09:02:01 2019 -0600
tree 408e5c91fcd34aaa19d71fb4c672d89bf3e9c756
parent fb5ccc98782f654778cb8d96ba8a998304f9a51f

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>

fs/io_uring.c

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 949c82a..32f6598 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2795,13 +2795,14 @@ static int io_ring_submit(struct io_ring_ctx *ctx, unsigned int to_submit)
 		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;
 }