CVE-2010-2955 kernel: wireless: fix 64K kernel heap content leak via ioctl

[Eugene Teo <eugene () redhat com>]

On 08/28/2010 05:02 AM, 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. :) 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.
>
> [1] http://forums.grsecurity.net/viewtopic.php?f=3&t=2290&start=0
> [2] http://grsecurity.net/~spender/wireless-infoleak-fix2.patch

http://lkml.org/lkml/2010/8/27/413
http://lkml.org/lkml/2010/8/30/351

fix: http://lkml.org/lkml/2010/8/30/146

Please use CVE-2010-2955.

Eugene

> Reported-by: Brad Spengler<spender () grsecurity net>
> Signed-off-by: Kees Cook<kees.cook () canonical com>
> ---
>   include/net/iw_handler.h |    1 -
>   net/wireless/wext-core.c |   26 ++------------------------
>   2 files changed, 2 insertions(+), 25 deletions(-)
>
> diff --git a/include/net/iw_handler.h b/include/net/iw_handler.h
> index 3afdb21..6c81f29 100644
> --- a/include/net/iw_handler.h
> +++ b/include/net/iw_handler.h
> @@ -277,7 +277,6 @@
>   #define IW_DESCR_FLAG_EVENT   0x0002  /* Generate an event on SET */
>   #define IW_DESCR_FLAG_RESTRICT        0x0004  /* GET : request is ROOT only */
>                                 /* SET : Omit payload from generated iwevent */
> -#define IW_DESCR_FLAG_NOMAX    0x0008  /* GET : no limit on request size */
>   /* Driver level flags */
>   #define IW_DESCR_FLAG_WAIT    0x0100  /* Wait for driver event */
>
> diff --git a/net/wireless/wext-core.c b/net/wireless/wext-core.c
> index 0ef17bc..55b1fd9 100644
> --- a/net/wireless/wext-core.c
> +++ b/net/wireless/wext-core.c
> @@ -82,7 +82,6 @@ static const struct iw_ioctl_description standard_ioctl[] = {
>                 .header_type    = IW_HEADER_TYPE_POINT,
>                 .token_size     = sizeof(struct iw_priv_args),
>                 .max_tokens     = 16,
> -               .flags          = IW_DESCR_FLAG_NOMAX,
>         },
>         [IW_IOCTL_IDX(SIOCSIWSTATS)] = {
>                 .header_type    = IW_HEADER_TYPE_NULL,
> @@ -134,7 +133,6 @@ static const struct iw_ioctl_description standard_ioctl[] = {
>                 .token_size     = sizeof(struct sockaddr) +
>                                   sizeof(struct iw_quality),
>                 .max_tokens     = IW_MAX_AP,
> -               .flags          = IW_DESCR_FLAG_NOMAX,
>         },
>         [IW_IOCTL_IDX(SIOCSIWSCAN)] = {
>                 .header_type    = IW_HEADER_TYPE_POINT,
> @@ -146,7 +144,6 @@ static const struct iw_ioctl_description standard_ioctl[] = {
>                 .header_type    = IW_HEADER_TYPE_POINT,
>                 .token_size     = 1,
>                 .max_tokens     = IW_SCAN_MAX_DATA,
> -               .flags          = IW_DESCR_FLAG_NOMAX,
>         },
>         [IW_IOCTL_IDX(SIOCSIWESSID)] = {
>                 .header_type    = IW_HEADER_TYPE_POINT,
> @@ -737,28 +734,9 @@ static int ioctl_standard_iw_point(struct iw_point *iwp, unsigned int cmd,
>                         return -EFAULT;
>                 /* Save user space buffer size for checking */
>                 user_length = iwp->length;
> -
> -               /* Don't check if user_length>  max to allow forward
> -                * compatibility. The test user_length<  min is
> -                * implied by the test at the end.
> -                */
> -
> -               /* Support for very large requests */
> -               if ((descr->flags&  IW_DESCR_FLAG_NOMAX)&&
> -                   (user_length>  descr->max_tokens)) {
> -                       /* Allow userspace to GET more than max so
> -                        * we can support any size GET requests.
> -                        * There is still a limit : -ENOMEM.
> -                        */
> -                       extra_size = user_length * descr->token_size;
> -
> -                       /* Note : user_length is originally a __u16,
> -                        * and token_size is controlled by us,
> -                        * so extra_size won't get negative and
> -                        * won't overflow...
> -                        */
> -               }
>         }
> +       /* Support for very large requests */
> +       extra_size = max(extra_size, iwp->length * descr->token_size);
>
>         /* kzalloc() ensures NULL-termination for essid_compat. */
>         extra = kzalloc(extra_size, GFP_KERNEL);


--
main(i) { putchar(182623909 >> (i-1) * 5&31|!!(i<7)<<6) && main(++i); }