[hardy,maverick CVE 1/1] agp: fix OOM and buffer overflow

[Tim Gardner]

On 05/26/2011 10:22 AM, Andy Whitcroft wrote:
> From: Vasiliy Kulikov<segoon at openwall.com>
>
> page_count is copied from userspace.  agp_allocate_memory() tries to
> check whether this number is too big, but doesn't take into account the
> wrap case.  Also agp_create_user_memory() doesn't check whether
> alloc_size is calculated from num_agp_pages variable without overflow.
> This may lead to allocation of too small buffer with following buffer
> overflow.
>
> Another problem in agp code is not addressed in the patch - kernel memory
> exhaustion (AGPIOC_RESERVE and AGPIOC_ALLOCATE ioctls).  It is not checked
> whether requested pid is a pid of the caller (no check in agpioc_reserve_wrap()).
> Each allocation is limited to 16KB, though, there is no per-process limit.
> This might lead to OOM situation, which is not even solved in case of the
> caller death by OOM killer - the memory is allocated for another (faked) process.
>
> Signed-off-by: Vasiliy Kulikov<segoon at openwall.com>
> Signed-off-by: Dave Airlie<airlied at redhat.com>
>
> CVE-2011-1747
> BugLink: http://bugs.launchpad.net/bugs/788700
> (cherry picked from commit b522f02184b413955f3bc952e3776ce41edc6355)
> Signed-off-by: Andy Whitcroft<apw at canonical.com>
> ---
>   drivers/char/agp/generic.c |    8 +++++++-
>   1 files changed, 7 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/char/agp/generic.c b/drivers/char/agp/generic.c
> index d2abf51..3d852bf 100644
> --- a/drivers/char/agp/generic.c
> +++ b/drivers/char/agp/generic.c
> @@ -122,6 +122,9 @@ static struct agp_memory *agp_create_user_memory(unsigned long num_agp_pages)
>   	struct agp_memory *new;
>   	unsigned long alloc_size = num_agp_pages*sizeof(struct page *);
>
> +	if (INT_MAX/sizeof(struct page *)<  num_agp_pages)
> +		return NULL;
> +
>   	new = kzalloc(sizeof(struct agp_memory), GFP_KERNEL);
>   	if (new == NULL)
>   		return NULL;
> @@ -241,11 +244,14 @@ struct agp_memory *agp_allocate_memory(struct agp_bridge_data *bridge,
>   	int scratch_pages;
>   	struct agp_memory *new;
>   	size_t i;
> +	int cur_memory;
>
>   	if (!bridge)
>   		return NULL;
>
> -	if ((atomic_read(&bridge->current_memory_agp) + page_count)>  bridge->max_memory_agp)
> +	cur_memory = atomic_read(&bridge->current_memory_agp);
> +	if ((cur_memory + page_count>  bridge->max_memory_agp) ||
> +	    (cur_memory + page_count<  page_count))
>   		return NULL;
>
>   	if (type>= AGP_USER_TYPES) {

Acked-by: Tim Gardner <tim.gardner at canonical.com>

-- 
Tim Gardner tim.gardner at canonical.com