From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E8630C282CE for ; Wed, 22 May 2019 20:03:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BA21320863 for ; Wed, 22 May 2019 20:03:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731378AbfEVUDI (ORCPT ); Wed, 22 May 2019 16:03:08 -0400 Received: from nautica.notk.org ([91.121.71.147]:49794 "EHLO nautica.notk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730075AbfEVTVq (ORCPT ); Wed, 22 May 2019 15:21:46 -0400 Received: by nautica.notk.org (Postfix, from userid 1001) id E8FC1C009; Wed, 22 May 2019 21:21:44 +0200 (CEST) Date: Wed, 22 May 2019 21:21:29 +0200 From: Dominique Martinet To: Bharath Vedartham Cc: ericvh@gmail.com, lucho@ionkov.net, v9fs-developer@lists.sourceforge.net, linux-kernel@vger.kernel.org Subject: Re: [PATCH] 9p/cache.c: Fix memory leak in v9fs_cache_session_get_cookie Message-ID: <20190522192129.GA30941@nautica> References: <20190522191655.GA4657@bharath12345-Inspiron-5559> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190522191655.GA4657@bharath12345-Inspiron-5559> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Bharath Vedartham wrote on Thu, May 23, 2019: > v9fs_cache_session_get_cookie assigns a random cachetag to > v9ses->cachetag, if the cachetag is not assigned previously. > > v9fs_random_cachetag allocates memory to v9ses->cachetag with kmalloc > and uses scnprintf to fill it up with a cachetag. > > But if scnprintf fails, v9ses->cachetag is not freed in the current code causing a memory leak. > > Fix this by freeing v9ses->cachetag it v9fs_random_cachetag fails. > > This was reported by syzbot, the link to the report is below: > https://syzkaller.appspot.com/bug?id=f012bdf297a7a4c860c38a88b44fbee43fd9bbf3 > > Reported-by: syzbot+3a030a73b6c1e9833815@syzkaller.appspotmail.com > Signed-off-by: Bharath Vedartham > --- > fs/9p/cache.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/fs/9p/cache.c b/fs/9p/cache.c > index 9eb3470..4463b91 100644 > --- a/fs/9p/cache.c > +++ b/fs/9p/cache.c > @@ -66,6 +66,7 @@ void v9fs_cache_session_get_cookie(struct v9fs_session_info *v9ses) > if (!v9ses->cachetag) { > if (v9fs_random_cachetag(v9ses) < 0) { > v9ses->fscache = NULL; > + kfree(v9ses->cachetag); I would also reset v9ses->cachetag to NULL just in case, v9fs_cache_session_get_cookie will use v9ses->cachetag as it is if it is not null and you were leaving an invalid pointer there I do not see any reason it could be called multiple times but v9fs_cache_session_get_cookie does not return any error (void function) so something later on could try to use that cachetag incorrectly later on Thanks, -- Dominique