linux-kernel - [RESEND][PATCH] gen_init_cpio: avoid stack overflow when expanding

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20121024205756.GA12419@www.outflux.net>
Date:	Wed, 24 Oct 2012 13:57:56 -0700
From:	Kees Cook <keescook@...omium.org>
To:	linux-kernel@...r.kernel.org
Cc:	Kees Cook <keescook@...omium.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Michal Marek <mmarek@...e.cz>,
	Brad Spengler <spender@...ecurity.net>,
	PaX Team <pageexec@...email.hu>
Subject: [RESEND][PATCH] gen_init_cpio: avoid stack overflow when expanding

Fix possible overflow of the buffer used for expanding environment
variables when building file list.

$ 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.

Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Michal Marek <mmarek@...e.cz>
Cc: Brad Spengler <spender@...ecurity.net>
Cc: PaX Team <pageexec@...email.hu>
Cc: stable@...r.kernel.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 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


-- 
Kees Cook
Chrome OS Security
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/