linux-kernel - [PATCH 4.2.y-ckt 197/273] sunrpc/cache: fix off-by-one in qword

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Message-Id: <1457391064-6660-198-git-send-email-kamal@canonical.com>
Date:	Mon,  7 Mar 2016 14:49:48 -0800
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Stefan Hajnoczi <stefanha@...hat.com>,
	"J . Bruce Fields" <bfields@...hat.com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 4.2.y-ckt 197/273] sunrpc/cache: fix off-by-one in qword_get()

4.2.8-ckt5 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

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: Kamal Mostafa <kamal@...onical.com>
---
 net/sunrpc/cache.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index 2928aff..8d79e70 100644
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -1218,7 +1218,7 @@ int qword_get(char **bpp, char *dest, int bufsize)
 	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]);
-- 
2.7.0