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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 652FEC04ABB for ; Thu, 13 Sep 2018 06:26:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1F5E820881 for ; Thu, 13 Sep 2018 06:26:33 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1F5E820881 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=i-love.sakura.ne.jp Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726799AbeIMLed (ORCPT ); Thu, 13 Sep 2018 07:34:33 -0400 Received: from www262.sakura.ne.jp ([202.181.97.72]:48529 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726415AbeIMLed (ORCPT ); Thu, 13 Sep 2018 07:34:33 -0400 Received: from fsav110.sakura.ne.jp (fsav110.sakura.ne.jp [27.133.134.237]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id w8D6QTqS073383; Thu, 13 Sep 2018 15:26:29 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav110.sakura.ne.jp (F-Secure/fsigk_smtp/530/fsav110.sakura.ne.jp); Thu, 13 Sep 2018 15:26:29 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/530/fsav110.sakura.ne.jp) Received: from [192.168.1.8] (softbank060157066051.bbtec.net [60.157.66.51]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id w8D6QLB8073341 (version=TLSv1.2 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Thu, 13 Sep 2018 15:26:29 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Subject: Re: [PATCH] selinux: Add __GFP_NOWARN to allocation at str_read() To: Paul Moore Cc: selinux@tycho.nsa.gov, syzbot+ac488b9811036cea7ea0@syzkaller.appspotmail.com, Eric Paris , linux-kernel@vger.kernel.org, peter.enderborg@sony.com, Stephen Smalley , syzkaller-bugs@googlegroups.com, linux-mm References: <000000000000038dab0575476b73@google.com> From: Tetsuo Handa Message-ID: Date: Thu, 13 Sep 2018 15:26:19 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2018/09/13 12:02, Paul Moore wrote: > On Fri, Sep 7, 2018 at 12:43 PM Tetsuo Handa > wrote: >> syzbot is hitting warning at str_read() [1] because len parameter can >> become larger than KMALLOC_MAX_SIZE. We don't need to emit warning for >> this case. >> >> [1] https://syzkaller.appspot.com/bug?id=7f2f5aad79ea8663c296a2eedb81978401a908f0 >> >> Signed-off-by: Tetsuo Handa >> Reported-by: syzbot >> --- >> security/selinux/ss/policydb.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/security/selinux/ss/policydb.c b/security/selinux/ss/policydb.c >> index e9394e7..f4eadd3 100644 >> --- a/security/selinux/ss/policydb.c >> +++ b/security/selinux/ss/policydb.c >> @@ -1101,7 +1101,7 @@ static int str_read(char **strp, gfp_t flags, void *fp, u32 len) >> if ((len == 0) || (len == (u32)-1)) >> return -EINVAL; >> >> - str = kmalloc(len + 1, flags); >> + str = kmalloc(len + 1, flags | __GFP_NOWARN); >> if (!str) >> return -ENOMEM; > > Thanks for the patch. > > My eyes are starting to glaze over a bit chasing down all of the > different kmalloc() code paths trying to ensure that this always does > the right thing based on size of the allocation and the different slab > allocators ... are we sure that this will always return NULL when (len > + 1) is greater than KMALLOC_MAX_SIZE for the different slab allocator > configurations? > Yes, for (len + 1) cannot become 0 (which causes kmalloc() to return ZERO_SIZE_PTR) due to (len == (u32)-1) check above. The only concern would be whether you want allocation failure messages. I assumed you don't need it because we are returning -ENOMEM to the caller.