linux-kernel - Re: Buffer overflow in CIFS VFS.

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Message-ID: <20071108222824.GD18903@lazybastard.org>
Date:	Thu, 8 Nov 2007 23:28:24 +0100
From:	Jörn Engel <joern@...fs.org>
To:	Przemyslaw Wegrzyn <czajnik@...jsoft.pl>
Cc:	linux-kernel@...r.kernel.org, Steve French <smfrench@...tin.rr.com>
Subject: Re: Buffer overflow in CIFS VFS.

Not everyone has the time to read lkml.  Added Steve to Cc:, just in
case.

On Thu, 8 November 2007 22:20:03 +0100, Przemyslaw Wegrzyn wrote:
> 
> I was looking at CIFS VFS code recently, trying to solve other issue,
> just to find something that looks like a buffer overflow  bug.
> The problem is in SendReceive() function in transport.c - it memcpy's
> message payload into a buffer passed via out_buf param. The function
> assumes that all buffers are of size (CIFSMaxBufSize +
> MAX_CIFS_HDR_SIZE) , unfortunately it is also called with smaller
> (MAX_CIFS_SMALL_BUFFER_SIZE) buffers.
> 
> To check this finding I patched Samba server to send oversized logoffX
> messages. With ~ 16kB messages the client running 2.6.23.1 crashed upon
> unmounting.
> 
> I've done a quick fix, available here:
> http://czajnick.sitenet.pl/cifs-buffer-overflow-fix.patch.gz

Jörn

-- 
When in doubt, punt.  When somebody actually complains, go back and fix it...
The 90% solution is a good thing.
-- Rob Landley
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