Re: [PATCH V4 1/2] ptr_ring: fail early if queue occupies more than KMALLOC_MAX_SIZE

[Jason Wang <jasowang@redhat.com>]

On 2018年02月11日 03:32, Eric Biggers wrote:
> 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

Good catch.

Will post a fix.

Thanks