linux-kernel - [PATCH v3] hex2bin: fix access beyond string end

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-prev] [day] [month] [year] [list]

Message-ID: <alpine.LRH.2.02.2204271112080.20348@file01.intranet.prod.int.rdu2.redhat.com>
Date:   Wed, 27 Apr 2022 11:26:40 -0400 (EDT)
From:   Mikulas Patocka <mpatocka@...hat.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
cc:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        device-mapper development <dm-devel@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Mike Snitzer <msnitzer@...hat.com>,
        Milan Broz <gmazyland@...il.com>
Subject: [PATCH v3] hex2bin: fix access beyond string end

If we pass too short string to "hex2bin" (and the string size without the
terminating NUL character is even), "hex2bin" reads one byte after the
terminating NUL character. This patch fixes it.

Note that hex_to_bin returns -1 on error and hex2bin return -EINVAL on
error - so we can't just return the variable "hi" or "lo" on error. This
inconsistency may be fixed in the next merge window, but for the purpose
of fixing this bug, we just preserve the existing behavior and return -1
and -EINVAL.

Signed-off-by: Mikulas Patocka <mpatocka@...hat.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>
Fixes: b78049831ffe ("lib: add error checking to hex2bin")
Cc: stable@...r.kernel.org

---
 lib/hexdump.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

Index: linux-2.6/lib/hexdump.c
===================================================================
--- linux-2.6.orig/lib/hexdump.c	2022-04-24 18:51:16.000000000 +0200
+++ linux-2.6/lib/hexdump.c	2022-04-27 17:16:38.000000000 +0200
@@ -45,10 +45,13 @@ EXPORT_SYMBOL(hex_to_bin);
 int hex2bin(u8 *dst, const char *src, size_t count)
 {
 	while (count--) {
-		int hi = hex_to_bin(*src++);
-		int lo = hex_to_bin(*src++);
+		int hi, lo;
 
-		if ((hi < 0) || (lo < 0))
+		hi = hex_to_bin(*src++);
+		if (unlikely(hi < 0))
+			return -EINVAL;
+		lo = hex_to_bin(*src++);
+		if (unlikely(lo < 0))
 			return -EINVAL;
 
 		*dst++ = (hi << 4) | lo;