io_uring/rsrc: fix rogue rsrc node grabbing

We should not be looking at ctx->rsrc_node and anyhow modifying the node
without holding uring_lock, grabbing references in such a way is not
safe either.

Cc: stable@vger.kernel.org
Fixes: 5106dd6 ("io_uring: propagate issue_flags state down to file assignment")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/1202ede2d7bb90136e3482b2b84aad9ed483e5d6.1680098433.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: isilence

io_uring/rsrc.h

@@ -144,15 +144,13 @@ static inline void io_req_set_rsrc_node(struct io_kiocb *req,
 					unsigned int issue_flags)
 {
 	if (!req->rsrc_node) {
-		req->rsrc_node = ctx->rsrc_node;
+		io_ring_submit_lock(ctx, issue_flags);
 
-		if (!(issue_flags & IO_URING_F_UNLOCKED)) {
-			lockdep_assert_held(&ctx->uring_lock);
+		lockdep_assert_held(&ctx->uring_lock);
 
-			io_charge_rsrc_node(ctx);
-		} else {
-			percpu_ref_get(&req->rsrc_node->refs);
-		}
+		req->rsrc_node = ctx->rsrc_node;
+		io_charge_rsrc_node(ctx);
+		io_ring_submit_unlock(ctx, issue_flags);
 	}
 }