[PATCH 5.16 0071/1039] io_uring: fix no lock protection for ctx->cq_extra

[Greg Kroah-Hartman]

From: Hao Xu <haoxu@xxxxxxxxxxxxxxxxx>

commit e302f1046f4c209291b07ff7bc4d15ca26891f16 upstream.

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

Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Hao Xu <haoxu@xxxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20211125092103.224502-2-haoxu@xxxxxxxxxxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 fs/io_uring.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -6544,12 +6544,15 @@ static __cold void io_drain_req(struct i
 	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) {