[Lucid, Karmic, Hardy] [PATCH] filter: make sure filters dont read uninitialized memory, CVE-2010-4158

[John Johansen]

On 02/18/2011 08:41 AM, Stefan Bader wrote:
> From: David S. Miller <davem at davemloft.net>
> 
> CVE-2010-4158
> BugLink: http://bugs.launchpad.net/bugs/721282
> 
> There is a possibility malicious users can get limited information about
> uninitialized stack mem array. Even if sk_run_filter() result is bound
> to packet length (0 .. 65535), we could imagine this can be used by
> hostile user.
> 
> Initializing mem[] array, like Dan Rosenberg suggested in his patch is
> expensive since most filters dont even use this array.
> 
> Its hard to make the filter validation in sk_chk_filter(), because of
> the jumps. This might be done later.
> 
> In this patch, I use a bitmap (a single long var) so that only filters
> using mem[] loads/stores pay the price of added security checks.
> 
> For other filters, additional cost is a single instruction.
> 
> [ Since we access fentry->k a lot now, cache it in a local variable
>   and mark filter entry pointer as const. -DaveM ]
> 
> Reported-by: Dan Rosenberg <drosenberg at vsecurity.com>
> Signed-off-by: Eric Dumazet <eric.dumazet at gmail.com>
> Signed-off-by: David S. Miller <davem at davemloft.net>
> 
> (backported from commit 57fe93b374a6b8711995c2d466c502af9f3a08bb upstream)
> Signed-off-by: Stefan Bader <stefan.bader at canonical.com>
Acked-by: John Johansen <john.johansen at canonical.com>