From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752267Ab3FDWlN (ORCPT ); Tue, 4 Jun 2013 18:41:13 -0400 Received: from 1wt.eu ([62.212.114.60]:35151 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751801Ab3FDWkq (ORCPT ); Tue, 4 Jun 2013 18:40:46 -0400 Message-Id: <20130604172130.677029877@1wt.eu> User-Agent: quilt/0.48-1 Date: Tue, 04 Jun 2013 19:21:39 +0200 From: Willy Tarreau To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Kees Cook , Michal Marek , Brad Spengler , PaX Team , Andrew Morton , Linus Torvalds , Greg Kroah-Hartman , Willy Tarreau Subject: [ 009/184] gen_init_cpio: avoid stack overflow when expanding In-Reply-To: <58df134a4b98edf5b0073e2e1e988fe6@local> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.32-longterm 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=$(perl -e 'print "A" x 4096;') ./usr/gen_init_cpio usr/crash.list *** buffer overflow detected ***: ./usr/gen_init_cpio terminated This also replaces the space-indenting with tabs. Patch based on existing fix extracted from grsecurity. Signed-off-by: Kees Cook Cc: Michal Marek Cc: Brad Spengler Cc: PaX Team Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman Signed-off-by: Willy Tarreau --- usr/gen_init_cpio.c | 43 +++++++++++++++++++++++-------------------- 1 file changed, 23 insertions(+), 20 deletions(-) diff --git a/usr/gen_init_cpio.c b/usr/gen_init_cpio.c index 83b3dde..13cd679 100644 --- a/usr/gen_init_cpio.c +++ b/usr/gen_init_cpio.c @@ -299,7 +299,7 @@ static int cpio_mkfile(const char *name, const char *location, int retval; int rc = -1; int namesize; - int i; + unsigned int i; mode |= S_IFREG; @@ -372,25 +372,28 @@ error: static char *cpio_replace_env(char *new_location) { - char expanded[PATH_MAX + 1]; - char env_var[PATH_MAX + 1]; - char *start; - char *end; - - for (start = NULL; (start = strstr(new_location, "${")); ) { - 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; } -- 1.7.12.2.21.g234cd45.dirty