From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753175AbeDKO1G (ORCPT ); Wed, 11 Apr 2018 10:27:06 -0400 Received: from mo4-p01-ob.smtp.rzone.de ([81.169.146.167]:11485 "EHLO mo4-p01-ob.smtp.rzone.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751491AbeDKO1E (ORCPT ); Wed, 11 Apr 2018 10:27:04 -0400 X-RZG-AUTH: :P2ERcEykfu11Y98lp/T7+hdri+uKZK8TKWEqNyiHySGSa9k9zW8BKRp5UFiyGZZ4jof7Xg== X-RZG-CLASS-ID: mo00 From: Stephan =?ISO-8859-1?Q?M=FCller?= To: Dmitry Vyukov Cc: "Theodore Y. Ts'o" , Matthew Wilcox , Herbert Xu , David Miller , linux-crypto@vger.kernel.org, Eric Biggers , syzbot , linux-fsdevel , LKML , syzkaller-bugs , Al Viro Subject: Re: [PATCH] crypto: DRBG - guard uninstantion by lock Date: Wed, 11 Apr 2018 16:26:18 +0200 Message-ID: <2186798.qrgUIDAn9S@positron.chronox.de> In-Reply-To: References: <001a114467482dbc4b05692df8f9@google.com> <2704286.80iLvC0rRL@tauon.chronox.de> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Dimitry, This fix prevents the kernel from crashing when injecting the fault. Stack traces are yet shown but I guess that is expected every time a fault is injected. As to why KASAN did not notice this one, I am not sure. Maybe it is because I use two buffer pointers to point to (almost) the same memory (one that is aligned and one pointing to the complete buffer)? ---8<--- During freeing of the internal buffers used by the DRBG, set the pointer to NULL. It is possible that the context with the freed buffers is reused. In case of an error during initialization where the pointers do not yet point to allocated memory, the NULL value prevents a double free. Signed-off-by: Stephan Mueller Reported-by: syzbot+75397ee3df5c70164154@syzkaller.appspotmail.com --- crypto/drbg.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/crypto/drbg.c b/crypto/drbg.c index 4faa2781c964..466a112a4446 100644 --- a/crypto/drbg.c +++ b/crypto/drbg.c @@ -1134,8 +1134,10 @@ static inline void drbg_dealloc_state(struct drbg_state *drbg) if (!drbg) return; kzfree(drbg->Vbuf); + drbg->Vbuf = NULL; drbg->V = NULL; kzfree(drbg->Cbuf); + drbg->Cbuf = NULL; drbg->C = NULL; kzfree(drbg->scratchpadbuf); drbg->scratchpadbuf = NULL; -- 2.14.3