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) { >