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    Subject[024/143] agp: fix OOM and buffer overflow
    2.6.32-longterm review patch.  If anyone has any objections, please let us know.


    From: Vasiliy Kulikov <>

    commit b522f02184b413955f3bc952e3776ce41edc6355 upstream.

    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

    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 <>
    Signed-off-by: Dave Airlie <>
    Signed-off-by: Greg Kroah-Hartman <>

    drivers/char/agp/generic.c | 8 +++++++-
    1 file changed, 7 insertions(+), 1 deletion(-)

    --- a/drivers/char/agp/generic.c
    +++ b/drivers/char/agp/generic.c
    @@ -123,6 +123,9 @@ static struct agp_memory *agp_create_use
    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;
    @@ -242,11 +245,14 @@ struct agp_memory *agp_allocate_memory(s
    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) {

     \ /
      Last update: 2011-05-06 02:27    [W:0.021 / U:2.904 seconds]
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