From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934219Ab2KZRQL (ORCPT ); Mon, 26 Nov 2012 12:16:11 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:48294 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934205Ab2KZRQG (ORCPT ); Mon, 26 Nov 2012 12:16:06 -0500 From: Herton Ronaldo Krzesinski To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Kees Cook , Michal Marek , Brad Spengler , PaX Team , Andrew Morton , Linus Torvalds , Herton Ronaldo Krzesinski Subject: [PATCH 259/270] gen_init_cpio: avoid stack overflow when expanding Date: Mon, 26 Nov 2012 14:59:09 -0200 Message-Id: <1353949160-26803-260-git-send-email-herton.krzesinski@canonical.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1353949160-26803-1-git-send-email-herton.krzesinski@canonical.com> References: <1353949160-26803-1-git-send-email-herton.krzesinski@canonical.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.5.7u1 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Kees Cook commit 20f1de659b77364d55d4e7fad2ef657e7730323f upstream. Fix possible overflow of the buffer used for expanding environment variables when building file list. In the extremely unlikely case of an attacker having control over the environment variables visible to gen_init_cpio, control over the contents of the file gen_init_cpio parses, and gen_init_cpio was built without compiler hardening, the attacker can gain arbitrary execution control via a stack buffer overflow. $ cat usr/crash.list file foo ${BIG}${BIG}${BIG}${BIG}${BIG}${BIG} 0755 0 0 $ BIG=$(perl -e 'print "A" x 4096;') ./usr/gen_init_cpio usr/crash.list *** buffer overflow detected ***: ./usr/gen_init_cpio terminated This also replaces the space-indenting with tabs. Patch based on existing fix extracted from grsecurity. Signed-off-by: Kees Cook Cc: Michal Marek Cc: Brad Spengler Cc: PaX Team Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Herton Ronaldo Krzesinski --- usr/gen_init_cpio.c | 43 +++++++++++++++++++++++-------------------- 1 file changed, 23 insertions(+), 20 deletions(-) diff --git a/usr/gen_init_cpio.c b/usr/gen_init_cpio.c index af0f22f..aca6edc 100644 --- a/usr/gen_init_cpio.c +++ b/usr/gen_init_cpio.c @@ -303,7 +303,7 @@ static int cpio_mkfile(const char *name, const char *location, int retval; int rc = -1; int namesize; - int i; + unsigned int i; mode |= S_IFREG; @@ -381,25 +381,28 @@ error: static char *cpio_replace_env(char *new_location) { - char expanded[PATH_MAX + 1]; - char env_var[PATH_MAX + 1]; - char *start; - char *end; - - for (start = NULL; (start = strstr(new_location, "${")); ) { - end = strchr(start, '}'); - if (start < end) { - *env_var = *expanded = '\0'; - strncat(env_var, start + 2, end - start - 2); - strncat(expanded, new_location, start - new_location); - strncat(expanded, getenv(env_var), PATH_MAX); - strncat(expanded, end + 1, PATH_MAX); - strncpy(new_location, expanded, PATH_MAX); - } else - break; - } - - return new_location; + char expanded[PATH_MAX + 1]; + char env_var[PATH_MAX + 1]; + char *start; + char *end; + + for (start = NULL; (start = strstr(new_location, "${")); ) { + end = strchr(start, '}'); + if (start < end) { + *env_var = *expanded = '\0'; + strncat(env_var, start + 2, end - start - 2); + strncat(expanded, new_location, start - new_location); + strncat(expanded, getenv(env_var), + PATH_MAX - strlen(expanded)); + strncat(expanded, end + 1, + PATH_MAX - strlen(expanded)); + strncpy(new_location, expanded, PATH_MAX); + new_location[PATH_MAX] = 0; + } else + break; + } + + return new_location; } -- 1.7.9.5