From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from list by lists.gnu.org with archive (Exim 4.71) id 1XdgvZ-0004IA-DB for mharc-qemu-trivial@gnu.org; Mon, 13 Oct 2014 10:48:49 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:55583) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XdgvQ-00046k-3U for qemu-trivial@nongnu.org; Mon, 13 Oct 2014 10:48:47 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XdgvI-0006pZ-Lc for qemu-trivial@nongnu.org; Mon, 13 Oct 2014 10:48:40 -0400 Received: from cantor2.suse.de ([195.135.220.15]:38518 helo=mx2.suse.de) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Xdgun-0006iV-HZ; Mon, 13 Oct 2014 10:48:01 -0400 Received: from relay2.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 749EAAB07; Mon, 13 Oct 2014 14:48:00 +0000 (UTC) Message-ID: <543BE616.1000707@suse.de> Date: Mon, 13 Oct 2014 16:47:50 +0200 From: Alexander Graf User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:31.0) Gecko/20100101 Thunderbird/31.1.2 MIME-Version: 1.0 To: Chen Gang , pbonzini@redhat.com References: <543BE352.3080609@gmail.com> In-Reply-To: <543BE352.3080609@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x (no timestamps) [generic] X-Received-From: 195.135.220.15 Cc: qemu-trivial@nongnu.org, qemu-ppc@nongnu.org, qemu-devel , kvm@vger.kernel.org Subject: Re: [Qemu-trivial] [PATCH] target-ppc: kvm: Fix memory overflow issue about strncat() X-BeenThere: qemu-trivial@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 13 Oct 2014 14:48:47 -0000 On 13.10.14 16:36, Chen Gang wrote: > strncat() will append additional '\0' to destination buffer, so need > additional 1 byte for it, or may cause memory overflow, just like other > area within QEMU have done. > > Signed-off-by: Chen Gang I agree with this patch. However, the code is pretty ugly - I'm sure it must've been me who wrote it :). Could you please instead rewrite it to use g_strdup_printf() rather than strncat()s? That way we resolve all string pitfalls automatically - and this code is not the fast path, so doing an extra memory allocation is ok. Alex > --- > target-ppc/kvm.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c > index 9c23c6b..66e7ce5 100644 > --- a/target-ppc/kvm.c > +++ b/target-ppc/kvm.c > @@ -1794,8 +1794,8 @@ static uint64_t kvmppc_read_int_cpu_dt(const char *propname) > return -1; > } > > - strncat(buf, "/", sizeof(buf) - strlen(buf)); > - strncat(buf, propname, sizeof(buf) - strlen(buf)); > + strncat(buf, "/", sizeof(buf) - strlen(buf) - 1); > + strncat(buf, propname, sizeof(buf) - strlen(buf) - 1); > > f = fopen(buf, "rb"); > if (!f) { > From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexander Graf Subject: Re: [PATCH] target-ppc: kvm: Fix memory overflow issue about strncat() Date: Mon, 13 Oct 2014 16:47:50 +0200 Message-ID: <543BE616.1000707@suse.de> References: <543BE352.3080609@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: qemu-ppc@nongnu.org, kvm@vger.kernel.org, qemu-devel , qemu-trivial@nongnu.org To: Chen Gang , pbonzini@redhat.com Return-path: Received: from cantor2.suse.de ([195.135.220.15]:57655 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753920AbaJMOsC (ORCPT ); Mon, 13 Oct 2014 10:48:02 -0400 In-Reply-To: <543BE352.3080609@gmail.com> Sender: kvm-owner@vger.kernel.org List-ID: On 13.10.14 16:36, Chen Gang wrote: > strncat() will append additional '\0' to destination buffer, so need > additional 1 byte for it, or may cause memory overflow, just like other > area within QEMU have done. > > Signed-off-by: Chen Gang I agree with this patch. However, the code is pretty ugly - I'm sure it must've been me who wrote it :). Could you please instead rewrite it to use g_strdup_printf() rather than strncat()s? That way we resolve all string pitfalls automatically - and this code is not the fast path, so doing an extra memory allocation is ok. Alex > --- > target-ppc/kvm.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c > index 9c23c6b..66e7ce5 100644 > --- a/target-ppc/kvm.c > +++ b/target-ppc/kvm.c > @@ -1794,8 +1794,8 @@ static uint64_t kvmppc_read_int_cpu_dt(const char *propname) > return -1; > } > > - strncat(buf, "/", sizeof(buf) - strlen(buf)); > - strncat(buf, propname, sizeof(buf) - strlen(buf)); > + strncat(buf, "/", sizeof(buf) - strlen(buf) - 1); > + strncat(buf, propname, sizeof(buf) - strlen(buf) - 1); > > f = fopen(buf, "rb"); > if (!f) { > From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:55457) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Xdguv-0003fF-7R for qemu-devel@nongnu.org; Mon, 13 Oct 2014 10:48:17 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Xdgun-0006ib-OY for qemu-devel@nongnu.org; Mon, 13 Oct 2014 10:48:09 -0400 Message-ID: <543BE616.1000707@suse.de> Date: Mon, 13 Oct 2014 16:47:50 +0200 From: Alexander Graf MIME-Version: 1.0 References: <543BE352.3080609@gmail.com> In-Reply-To: <543BE352.3080609@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] target-ppc: kvm: Fix memory overflow issue about strncat() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Chen Gang , pbonzini@redhat.com Cc: qemu-trivial@nongnu.org, qemu-ppc@nongnu.org, qemu-devel , kvm@vger.kernel.org On 13.10.14 16:36, Chen Gang wrote: > strncat() will append additional '\0' to destination buffer, so need > additional 1 byte for it, or may cause memory overflow, just like other > area within QEMU have done. > > Signed-off-by: Chen Gang I agree with this patch. However, the code is pretty ugly - I'm sure it must've been me who wrote it :). Could you please instead rewrite it to use g_strdup_printf() rather than strncat()s? That way we resolve all string pitfalls automatically - and this code is not the fast path, so doing an extra memory allocation is ok. Alex > --- > target-ppc/kvm.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c > index 9c23c6b..66e7ce5 100644 > --- a/target-ppc/kvm.c > +++ b/target-ppc/kvm.c > @@ -1794,8 +1794,8 @@ static uint64_t kvmppc_read_int_cpu_dt(const char *propname) > return -1; > } > > - strncat(buf, "/", sizeof(buf) - strlen(buf)); > - strncat(buf, propname, sizeof(buf) - strlen(buf)); > + strncat(buf, "/", sizeof(buf) - strlen(buf) - 1); > + strncat(buf, propname, sizeof(buf) - strlen(buf) - 1); > > f = fopen(buf, "rb"); > if (!f) { >