[PATCH 5.15 045/262] io_uring: fix no lock protection for ctx->cq_extra

[Greg Kroah-Hartman]

From: Hao Xu <haoxu@xxxxxxxxxxxxxxxxx>

[ Upstream commit e302f1046f4c209291b07ff7bc4d15ca26891f16 ]

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: Sasha Levin <sashal@xxxxxxxxxx>
---
 fs/io_uring.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index d7e49e87b49b9..156c54ebb62b7 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -6573,11 +6573,14 @@ static bool io_drain_req(struct io_kiocb *req)
 	}
 
 	/* Still need defer if there is pending req in defer list. */
+	spin_lock(&ctx->completion_lock);
 	if (likely(list_empty_careful(&ctx->defer_list) &&
 		!(req->flags & REQ_F_IO_DRAIN))) {
+		spin_unlock(&ctx->completion_lock);
 		ctx->drain_active = false;
 		return false;
 	}
+	spin_unlock(&ctx->completion_lock);
 
 	seq = io_get_sequence(req);
 	/* Still a chance to pass the sequence check */
-- 
2.34.1