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Date: Fri, 19 Aug 2011 23:28:31 +0800
From: Eugene Teo <eugene@...hat.com>
To: oss-security@...ts.openwall.com
CC: Timo Warns <warns@...-sense.de>
Subject: Re: CVE request: Linux: ZERO_SIZE_PTR dereference
 for long symlinks in Be FS

On 08/19/2011 03:18 PM, Timo Warns wrote:
> The Linux kernel contains a vulnerability in the driver for Be file
> systems that may lead to a kernel oops via a corrupted Be file system.
> 
> In fs/befs/linuxvfs.c, befs_follow_link() reads a length attribute for
> a long symlink from a data stream of a Be file system.
> 
>     befs_data_stream *data = &befs_ino->i_data.ds;
>     befs_off_t len = data->size;
> 
> The data->size / len value is not validated and can be 0 on a corrupted
> file system.
> 
> befs_follow_link() allocates some memory based on len. Effectively,
> kmalloc returns ZERO_SIZE_PTR in this case.
> 
>         link = kmalloc(len, GFP_NOFS);
> 
> Subsequently, an assignment dereferences ZERO_SIZE_PTR causing a kernel
> oops:
> 
> 			link[len - 1] = '\0';
> 
> A patch is available at
> http://git.kernel.org/linus/338d0f0a6fbc82407864606f5b64b75aeb3c70f2

Please use CVE-2011-2928.

Eugene

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