linux-kernel - [PATCH 3.2 35/62] sunrpc/cache: fix off-by-one in qword

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Message-ID: <lsq.1459279102.802059964@decadent.org.uk>
Date:	Tue, 29 Mar 2016 20:18:22 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Stefan Hajnoczi" <stefanha@...hat.com>,
	"J. Bruce Fields" <bfields@...hat.com>
Subject: [PATCH 3.2 35/62] sunrpc/cache: fix off-by-one in qword_get()

3.2.79-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Stefan Hajnoczi <stefanha@...hat.com>

commit b7052cd7bcf3c1478796e93e3dff2b44c9e82943 upstream.

The qword_get() function NUL-terminates its output buffer.  If the input
string is in hex format \xXXXX... and the same length as the output
buffer, there is an off-by-one:

  int qword_get(char **bpp, char *dest, int bufsize)
  {
      ...
      while (len < bufsize) {
          ...
          *dest++ = (h << 4) | l;
          len++;
      }
      ...
      *dest = '\0';
      return len;
  }

This patch ensures the NUL terminator doesn't fall outside the output
buffer.

Signed-off-by: Stefan Hajnoczi <stefanha@...hat.com>
Signed-off-by: J. Bruce Fields <bfields@...hat.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 net/sunrpc/cache.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -1211,7 +1211,7 @@ int qword_get(char **bpp, char *dest, in
 	if (bp[0] == '\\' && bp[1] == 'x') {
 		/* HEX STRING */
 		bp += 2;
-		while (len < bufsize) {
+		while (len < bufsize - 1) {
 			int h, l;
 
 			h = hex_to_bin(bp[0]);