linux-kernel - [ 04/54] 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 for Android: free password hash cracker in your pocket

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

Message-Id: <20121029213803.239923186@linuxfoundation.org>
Date:	Mon, 29 Oct 2012 14:40:05 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	alan@...rguk.ukuu.org.uk, Kees Cook <keescook@...omium.org>,
	Michal Marek <mmarek@...e.cz>,
	Brad Spengler <spender@...ecurity.net>,
	PaX Team <pageexec@...email.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [ 04/54] gen_init_cpio: avoid stack overflow when expanding

3.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Kees Cook <keescook@...omium.org>

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 <keescook@...omium.org>
Cc: Michal Marek <mmarek@...e.cz>
Cc: Brad Spengler <spender@...ecurity.net>
Cc: PaX Team <pageexec@...email.hu>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 usr/gen_init_cpio.c |   41 ++++++++++++++++++++++-------------------
 1 file changed, 22 insertions(+), 19 deletions(-)

--- a/usr/gen_init_cpio.c
+++ b/usr/gen_init_cpio.c
@@ -303,7 +303,7 @@ static int cpio_mkfile(const char *name,
 	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, "${")); ) {
-               end = strchr(start, '}');
-               if (start < end) {
-                       *env_var = *expanded = '\0';
-                       strncat(env_var, start + 2, end - start - 2);
-                       strncat(expanded, new_location, start - new_location);
-                       strncat(expanded, getenv(env_var), PATH_MAX);
-                       strncat(expanded, end + 1, PATH_MAX);
-                       strncpy(new_location, expanded, PATH_MAX);
-               } else
-                       break;
-       }
+	char expanded[PATH_MAX + 1];
+	char env_var[PATH_MAX + 1];
+	char *start;
+	char *end;
+
+	for (start = NULL; (start = strstr(new_location, "${")); ) {
+		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;
+	return new_location;
 }
 
 


--
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/