oss-security - Re: CVE request - kernel: cifs: Fix a kernel BUG with remote OS/2 server

Openwall GNU/*/Linux - a small security-enhanced Linux distro for servers

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Date: Mon, 28 Jun 2010 16:23:37 -0400 (EDT)
From: Josh Bressers <bressers@...hat.com>
To: oss-security@...ts.openwall.com
Cc: "Steven M. Christey" <coley@...us.mitre.org>
Subject: Re: CVE request - kernel: cifs: Fix a kernel BUG
 with remote OS/2 server

Please use CVE-2010-2248

Thanks.

-- 
    JB


----- "Eugene Teo" <eugeneteo@...nel.sg> wrote:

> "This was known to trigger with a OS/2 server. The server sets 
> pSMBr->CountHigh to a incorrect value even in case of normal writes. 
> This results in 'nbytes' being computed wrongly and triggers a kernel
> 
> BUG at mm/filemap.c.
> 
>      void iov_iter_advance(struct iov_iter *i, size_t bytes)
>      {
>              BUG_ON(i->count < bytes);    <--- BUG here
> 
> Why the server is setting 'CountHigh' is not clear but only does so 
> after writing 64k bytes. Though this looks like the server bug, the 
> client side crash may not be acceptable.
> 
> The workaround is to mask off high 16 bits if the number of bytes 
> written as returned by the server is greater than the bytes requested
> by 
> the client."
> 
> https://bugzilla.redhat.com/show_bug.cgi?id=608583
> http://git.kernel.org/linus/6513a81e9325d712f1bfb9a1d7b750134e49ff18
> 
> -- 
> main(i) { putchar(182623909 >> (i-1) * 5&31|!!(i<7)<<6) && main(++i);
> }

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