Re: [PATCH] wireless: fix 64K kernel heap content leak via ioctl

Luis R. Rodriguez
2010-08-27T22:35:41Z

On Fri, Aug 27, 2010 at 2:22 PM, Jean Tourrilhes <jt@hpl.hp.com> wrote:
> On Fri, Aug 27, 2010 at 02:02:41PM -0700, Kees Cook wrote:
>> This problem was originally tracked down by Brad Spengler.
>>
>> When calling wireless ioctls, if a driver does not correctly
>> validate/shrink iwp->length, the resulting copy_to_user can leak up to
>> 64K of kernel heap contents.
>>
>> It seems that this is triggerable[1] in 2.6.32 at least on ath5k, but
>> I was not able to track down how. The twisty maze of ioctl handlers
>> stumped me. :)
>
>        You can always ask.
>
>> Other drivers I checked did not appear to have any problems,
>> but the potential remains. I'm not sure if this patch is the right approach;
>> it was fixed differently[2] in grsecurity.
>
>        Did you tried your patch for real ? With large scan request ?
>        I ask because at first glance, it looks incorrect, asI believe
> it kills large request. But someone would need to test, for sure.
>
>> [1] http://forums.grsecurity.net/viewtopic.php?f=3&t=2290&start=0
>> [2] http://grsecurity.net/~spender/wireless-infoleak-fix2.patch
>
>        I believe this patch would make the situation worse.
>
>        Would you mind validating the following patch ? I've just
> verified that it compiles and I believe it does what you are asking in
> a much more predictable way.
>        Regards,
>
>        Jean
>
> diff -u -p wext.j2.c wext.c
> --- wext.j2.c 2010-08-27 14:17:26.000000000 -0700
> +++ wext.c 2010-08-27 14:19:33.000000000 -0700
> @@ -800,9 +800,12 @@ static int ioctl_standard_iw_point(struc
> goto out;
> }
>
> - if (copy_to_user(iwp->pointer, extra,
> - iwp->length *
> - descr->token_size)) {
> + /* Verify how much we should return. Some driver
> + * may abuse iwp->length... */
> + if((iwp->length * descr->token_size) < extra_size)
> + extra_size = iwp->length * descr->token_size;
> +
> + if (copy_to_user(iwp->pointer, extra, extra_size)) {
> err = -EFAULT;
> goto out;
> }

Jean, can you submit in a new thread and right before the SOB add in
the commit log Cc: stable@kernel.org [2.6.32+]

Luis