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SubjectRe: [PATCH V4 1/2] ptr_ring: fail early if queue occupies more than KMALLOC_MAX_SIZE
Hi Jason,

On Fri, Feb 09, 2018 at 05:45:49PM +0800, Jason Wang wrote:
> To avoid slab to warn about exceeded size, fail early if queue
> occupies more than KMALLOC_MAX_SIZE.
>
> Reported-by: syzbot+e4d4f9ddd4295539735d@syzkaller.appspotmail.com
> Fixes: 2e0ab8ca83c12 ("ptr_ring: array based FIFO for pointers")
> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---
> include/linux/ptr_ring.h | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/include/linux/ptr_ring.h b/include/linux/ptr_ring.h
> index 1883d61..6051a5f 100644
> --- a/include/linux/ptr_ring.h
> +++ b/include/linux/ptr_ring.h
> @@ -466,6 +466,8 @@ 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)
> + return NULL;

Are you sure that size can't be over 0x40000000? The proper way to write this
(safe from integer overflow) would be:

if (size > KMALLOC_MAX_SIZE / sizeof(void *))
return NULL;

- Eric

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