From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37995) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XdhpJ-00021H-V1 for qemu-devel@nongnu.org; Mon, 13 Oct 2014 11:46:34 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XdhpA-0000F0-Pn for qemu-devel@nongnu.org; Mon, 13 Oct 2014 11:46:25 -0400 Message-ID: <543BF32F.4020205@gmail.com> Date: Mon, 13 Oct 2014 23:43:43 +0800 From: Chen Gang MIME-Version: 1.0 References: <543BE352.3080609@gmail.com> <543BE616.1000707@suse.de> In-Reply-To: <543BE616.1000707@suse.de> 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: Alexander Graf , pbonzini@redhat.com Cc: qemu-trivial@nongnu.org, qemu-ppc@nongnu.org, qemu-devel , kvm@vger.kernel.org On 10/13/14 22:47, Alexander Graf wrote: > > 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. > I guess, it is a personal taste. For me, it may need additional variable for g_strdup_printf(), and not save code lines, but *sprintf() is more readable than str*cat(). The related code may like below (welcome any improvement for it): diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c index 66e7ce5..cea6a87 100644 --- a/target-ppc/kvm.c +++ b/target-ppc/kvm.c @@ -1782,7 +1782,7 @@ static int kvmppc_find_cpu_dt(char *buf, int buf_len) * format) */ static uint64_t kvmppc_read_int_cpu_dt(const char *propname) { - char buf[PATH_MAX]; + char buf[PATH_MAX], *tmp; union { uint32_t v32; uint64_t v64; @@ -1794,10 +1794,10 @@ static uint64_t kvmppc_read_int_cpu_dt(const char *propname) return -1; } - strncat(buf, "/", sizeof(buf) - strlen(buf) - 1); - strncat(buf, propname, sizeof(buf) - strlen(buf) - 1); + tmp = g_strdup_printf("%s/%s", buf, propname); - f = fopen(buf, "rb"); + f = fopen(tmp, "rb"); + g_free(buf); if (!f) { return -1; } For me, it is really a personal taste, so if the maintainer feels the diff above is OK, I shall send patch v2 for it within 2 days. Thanks. -- Chen Gang Open, share, and attitude like air, water, and life which God blessed