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 <[email protected]> Signed-off-by: Jens Axboe <[email protected]>
ambv · Oct 25, 2019 · 935d1e4 · 935d1e4
1 parent fb5ccc9
commit 935d1e4
Showing 1 changed file with 2 additions and 1 deletion.
diff --git 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;
 }