Re: [patch] Fix handling of overlength pathname in AF_UNIX sun_path

On Wed, Apr 18, 2012 at 09:17:26AM +0100, David Laight wrote:

quoted

Why not have:

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index d510353..f9f77a7 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c

@@ -216,6 +216,9 @@ static int unix_mkname(struct sockaddr_un

*sunaddr, int len, unsigned *hashp)
                 */
                ((char *)sunaddr)[len] = 0;
                len = strlen(sunaddr->sun_path)+1+sizeof(short);
+               /* No null terminator was found in the path. */
+               if (len > sizeof(*sunaddr))
+                       return -EINVAL;
                return len;

That could generate a kernel page fault!
(Depending on what follows (or rather doesn't follow!) sun_path.)
You'd need to use memchr() not strlen().

	David

Hi, David.

What follows is a 0 byte, because it's set that way in the line before
strlen. Note that len is tested for sizeof(*sunaddr), and there is a
huge comment about that extra byte that was omitted.

The whole function is at net/unix/af_unix.c:203.

Regards,
Cascardo.