Re: [PATCH] splice: fix user pointer access in get_iovec_page_array()

["Oliver Pinter" <oliver.pntr@gmail.com>]

Signed-off-by: Oliver Pinter <oliver.pntr@gmail.com>

----8<----

Linux pancs 2.6.22.17-opt2-cve2 #1 SMP Sun Feb 10 16:22:37 CET 2008
i686 GNU/Linux
-----------------------------------
 Linux vmsplice Local Root Exploit
 By qaaz
-----------------------------------
[+] mmap: 0x0 .. 0x1000
[+] page: 0x0
[+] page: 0x20
[+] mmap: 0x4000 .. 0x5000
[+] page: 0x4000
[+] page: 0x4020
[+] mmap: 0x1000 .. 0x2000
[+] page: 0x1000
[+] mmap: 0xb7f2d000 .. 0xb7f5f000
[-] vmsplice: Bad address

-----

oliver@pancs:/tmp$ uname -a && ./2623_2624_root_exploit
Linux pancs 2.6.22.17-opt2-cve2 #1 SMP Sun Feb 10 16:22:37 CET 2008
i686 GNU/Linux
-----------------------------------
 Linux vmsplice Local Root Exploit
 By qaaz
-----------------------------------
[+] addr: 0xc01112e9
[-] wtf


---->8----
On 2/10/08, Bastian Blank <bastian@waldi.eu.org> wrote:
> On Sun, Feb 10, 2008 at 04:47:57PM +0200, Pekka J Enberg wrote:
> > From: Bastian Blank <bastian@waldi.eu.org>
> >
> > The commit 8811930dc74a503415b35c4a79d14fb0b408a361 ("splice: missing user
> > pointer access verification") added access_ok() to
> copy_from_user_mmap_sem()
> > which only ensures we can copy the struct iovecs from userspace to the
> kernel
> > but we also must check whether we can access the actual memory region
> pointed
> > to by the struct iovec to close the local root exploit.
> >
> > Cc: <stable@kernel.org>
> > Cc: Jens Axboe <jens.axboe@oracle.com>
> > Cc: Andrew Morton <akpm@linux-foundation.org>
> > Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
> Signed-off-by: Bastian Blank <waldi@debian.org>
>
> > Index: linux-2.6/fs/splice.c
> > ===================================================================
> > --- linux-2.6.orig/fs/splice.c
> > +++ linux-2.6/fs/splice.c
> > @@ -1237,6 +1237,9 @@ static int get_iovec_page_array(const st
> >  		if (unlikely(!base))
> >  			break;
> >
> > +		if (unlikely(!access_ok(VERIFY_READ, base, len)))
> > +			break;
> > +
> >  		/*
> >  		 * Get this base offset and number of pages, then map
> >  		 * in the user pages.
>
> --
> Those who hate and fight must stop themselves -- otherwise it is not
> stopped.
> 		-- Spock, "Day of the Dove", stardate unknown
>


-- 
Thanks,
Oliver