[PATCH 1/2] io_uring: fix no lock protection for ctx->cq_extra

[Hao Xu <haoxu@linux.alibaba.com>]

ctx->cq_extra should be protected by completion lock so that the
req_need_defer() does the right check.

Cc: stable@vger.kernel.org
Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
---
 fs/io_uring.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index f666a0e7f5e8..ae9534382b26 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -6537,12 +6537,15 @@ static __cold void io_drain_req(struct io_kiocb *req)
 	u32 seq = io_get_sequence(req);
 
 	/* Still need defer if there is pending req in defer list. */
+	spin_lock(&ctx->completion_lock);
 	if (!req_need_defer(req, seq) && list_empty_careful(&ctx->defer_list)) {
+		spin_unlock(&ctx->completion_lock);
 queue:
 		ctx->drain_active = false;
 		io_req_task_queue(req);
 		return;
 	}
+	spin_unlock(&ctx->completion_lock);
 
 	ret = io_req_prep_async(req);
 	if (ret) {
-- 
2.24.4