sunrpc/cache: fix off-by-one in qword_get()

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@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index 7de935a..51b23bc 100644 (file)
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -1211,7 +1211,7 @@ int qword_get(char **bpp, char *dest, int bufsize)
        if (bp[0] == '\\' && bp[1] == 'x') {
                /* HEX STRING */
                bp += 2;
        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]);
                        int h, l;
 
                        h = hex_to_bin(bp[0]);