io_uring: fix potential crash issue due to io_get_req failure

Sometimes io_get_req will return a NUL, then we need to do the
correct error handling, otherwise it will cause the kernel null
pointer exception.

Fixes: 4fe2c963154c ("io_uring: add support for link with drain")
Signed-off-by: Jackie Liu <liuyun01@kylinos.cn>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index f9139f5bd158016192850989cbbafbb11eeed904..854dedd885fa8ddce8e4d2c9a8efee45f7cb3b5a 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2364,12 +2364,15 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, struct sqe_submit *sqes,
                if (link && (sqes[i].sqe->flags & IOSQE_IO_DRAIN)) {
                        if (!shadow_req) {
                                shadow_req = io_get_req(ctx, NULL);
+                               if (unlikely(!shadow_req))
+                                       goto out;
                                shadow_req->flags |= (REQ_F_IO_DRAIN | REQ_F_SHADOW_DRAIN);
                                refcount_dec(&shadow_req->refs);
                        }
                        shadow_req->sequence = sqes[i].sequence;
                }
 
+out:
                if (unlikely(mm_fault)) {
                        io_cqring_add_event(ctx, sqes[i].sqe->user_data,
                                                -EFAULT);
@@ -2551,12 +2554,15 @@ static int io_ring_submit(struct io_ring_ctx *ctx, unsigned int to_submit,
                if (link && (s.sqe->flags & IOSQE_IO_DRAIN)) {
                        if (!shadow_req) {
                                shadow_req = io_get_req(ctx, NULL);
+                               if (unlikely(!shadow_req))
+                                       goto out;
                                shadow_req->flags |= (REQ_F_IO_DRAIN | REQ_F_SHADOW_DRAIN);
                                refcount_dec(&shadow_req->refs);
                        }
                        shadow_req->sequence = s.sequence;
                }
 
+out:
                s.has_user = true;
                s.needs_lock = false;
                s.needs_fixed_file = false;