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SubjectRe: [PATCH net] ptr_ring: prevent integer overflow when calculating size
On Sun, Feb 11, 2018 at 11:28:12AM +0800, Jason Wang wrote:
> Switch to use dividing to prevent integer overflow when size is too
> big to calculate allocation size properly.
>
> Reported-by: Eric Biggers <ebiggers3@gmail.com>
> Fixes: 6e6e41c31122 ("ptr_ring: fail early if queue occupies more than KMALLOC_MAX_SIZE")
> Signed-off-by: Jason Wang <jasowang@redhat.com>

Acked-by: Michael S. Tsirkin <mst@redhat.com>

> ---
> include/linux/ptr_ring.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/ptr_ring.h b/include/linux/ptr_ring.h
> index b884b77..e633522 100644
> --- a/include/linux/ptr_ring.h
> +++ b/include/linux/ptr_ring.h
> @@ -469,7 +469,7 @@ static inline int ptr_ring_consume_batched_bh(struct ptr_ring *r,
> */
> static inline void **__ptr_ring_init_queue_alloc(unsigned int size, gfp_t gfp)
> {
> - if (size * sizeof(void *) > KMALLOC_MAX_SIZE)
> + if (size > KMALLOC_MAX_SIZE / sizeof(void *))
> return NULL;
> return kvmalloc_array(size, sizeof(void *), gfp | __GFP_ZERO);
> }
> --
> 2.7.4

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