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

[Assar <assar@permabit.com>]

Hi, Marcelo.

Marcelo Tosatti <marcelo.tosatti@cyclades.com> writes:
> > diff -u linux-2.4.31.orig/fs/nfs/nfs2xdr.c linux-2.4.31/fs/nfs/nfs2xdr.c
> > --- linux-2.4.31.orig/fs/nfs/nfs2xdr.c	2002-11-28 18:53:15.000000000 -0500
> > +++ linux-2.4.31/fs/nfs/nfs2xdr.c	2005-09-12 16:12:30.000000000 -0400
> > @@ -571,8 +571,8 @@
> >  	strlen = (u32*)kmap(rcvbuf->pages[0]);
> >  	/* Convert length of symlink */
> >  	len = ntohl(*strlen);
> > -	if (len > rcvbuf->page_len)
> > -		len = rcvbuf->page_len;
> > +	if (len > rcvbuf->page_len - sizeof(*strlen) - 1)
> > +		len = rcvbuf->page_len - sizeof(*strlen) - 1;
> 
> So the problem is that the "len" variable encapsulated in (u32 *)rcvbuf->pages[0]
> does not account for its own length (4 bytes)? 

That's one problem.

> If thats the reason, you don't need the "-1" there?

It also writes a 0 byte.  I think it looks like this:

---- ------------ -
len  string...    0

-
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