Re: [PATCH] nfs client, kernel 2.4.31: readlink result overflow

[Peter Staubach <staubach@redhat.com>]

Assar wrote:

>>The 2.6 kernel code is also broken, but in a different, but once again,
>>similar fashions.
>>    
>>
>
>You mean for length > 1024 ?
>
>diff -u linux-2.6.13.orig/fs/nfs/nfs2xdr.c linux-2.6.13/fs/nfs/nfs2xdr.c
>--- linux-2.6.13.orig/fs/nfs/nfs2xdr.c	2005-08-28 19:41:01.000000000 -0400
>+++ linux-2.6.13/fs/nfs/nfs2xdr.c	2005-09-14 15:40:13.000000000 -0400
>@@ -557,7 +557,7 @@
> 		return -nfs_stat_to_errno(status);
> 	/* Convert length of symlink */
> 	len = ntohl(*p++);
>-	if (len >= rcvbuf->page_len || len <= 0) {
>+	if (len >= rcvbuf->page_len || len <= 0 || len > NFS2_MAXPATHLEN) {
> 		dprintk(KERN_WARNING "nfs: server returned giant symlink!\n");
> 		return -ENAMETOOLONG;
> 	}
>

This code appears to assume that rcvbuf->page_base is zero here, but then
uses rcvbuf->page_base when calculating where to place the null byte.  It
seems to me that it should either use rcvbuf->page_base in both
calculations or neither.

    Thanx...

       ps