From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 45FC9290F for ; Wed, 24 Jul 2024 00:45:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721781941; cv=none; b=o7yoKY0aPBwUIcq9U2cmqflV4becdzx6INDCKXJSxZa8gUyoiztTCec5UJbTtWaIaH54xoTx1knSVXcyACU2s2VVoEsQ2EQMTu8egJTLzUV//iT+m3YXbQydNGKGoJRlUr1eNfXYEMrPNfDTeTj9wgn0PA2qif5wvIZpi7SE03k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721781941; c=relaxed/simple; bh=u3uumP4MHFlL3hT8/wvedCGQVg5+0l9gdaNJM+2XbEw=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=GndxoMZkvgY/Z8+TtJkbzS6RH5h3CK1pL0GdUKFBYXHMoJ9RHpZYXOeeIw1UTca7J0sBJbUv0ePLxJpJ2++1+QZzTM0z4ZRDz+uZLaRrKMTOMv0v9ptTqlAe3z2CCg8Ibts/aBSiC525098+fZs6B5HxAZUWIoh8QF0iN8BNUFA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=PDzi1+VL; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="PDzi1+VL" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9B8F4C4AF09; Wed, 24 Jul 2024 00:45:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1721781940; bh=u3uumP4MHFlL3hT8/wvedCGQVg5+0l9gdaNJM+2XbEw=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=PDzi1+VLLmSujDjEVon2iNCXriDaRO4DoXcyMUgPLAtiPuzH8pkd9n8uGuyP0n1dG 2Z81g5QCxhFDUvds7Vy4GKWqSKyu3WkCekL7OujQUqX1eJf3O4FAxbJsn83WeXjq9a 6bQ8IyJB6zWU353RAh1LBnhebEwQPu9RzGP/w38s= Date: Tue, 23 Jul 2024 17:45:40 -0700 From: Andrew Morton To: Muchun Song Cc: hannes@cmpxchg.org, muchun.song@linux.dev, nphamcs@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: list_lru: fix UAF for memory cgroup Message-Id: <20240723174540.18992614c476d77e7d9fb1e6@linux-foundation.org> In-Reply-To: <20240718083607.42068-1-songmuchun@bytedance.com> References: <20240718083607.42068-1-songmuchun@bytedance.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Thu, 18 Jul 2024 16:36:07 +0800 Muchun Song wrote: > The mem_cgroup_from_slab_obj() is supposed to be called under rcu > lock or cgroup_mutex or others which could prevent returned memcg > from being freed. Fix it by adding missing rcu read lock. "or others" is rather vague. What others? > @@ -109,14 +110,20 @@ EXPORT_SYMBOL_GPL(list_lru_add); > > bool list_lru_add_obj(struct list_lru *lru, struct list_head *item) > { > + bool ret; > int nid = page_to_nid(virt_to_page(item)); > - struct mem_cgroup *memcg = list_lru_memcg_aware(lru) ? > - mem_cgroup_from_slab_obj(item) : NULL; > + struct mem_cgroup *memcg; > > - return list_lru_add(lru, item, nid, memcg); > + rcu_read_lock(); > + memcg = list_lru_memcg_aware(lru) ? mem_cgroup_from_slab_obj(item) : NULL; > + ret = list_lru_add(lru, item, nid, memcg); > + rcu_read_unlock(); We don't need rcu_read_lock() to evaluate NULL. memcg = NULL; if (list_lru_memcg_aware(lru)) { rcu_read_lock(); memcg = mem_cgroup_from_slab_obj(item); rcu_read_unlock(); } Seems worthwhile?