io_uring: fix no lock protection for ctx->cq_extra

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>
Link: https://lore.kernel.org/r/20211125092103.224502-2-haoxu@linux.alibaba.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index f666a0e..ae95343 100644 (file)
--- 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) {