Re: [PATCH net V3 2/2] ptr_ring: fail on large queue size (>64K)

From: Jason Wang <jasowang@redhat.com>
To: David Miller <davem@davemloft.net>
Cc: mst@redhat.com, netdev@vger.kernel.org
Subject: Re: [PATCH net V3 2/2] ptr_ring: fail on large queue size (>64K)
Date: Fri, 9 Feb 2018 11:51:02 +0800	[thread overview]
Message-ID: <b5edecb1-f81a-2cb1-e394-6bfde6d82640@redhat.com> (raw)
In-Reply-To: <20180208.140959.1771270473230462281.davem@davemloft.net>

On 2018年02月09日 03:09, David Miller wrote:
> From: Jason Wang <jasowang@redhat.com>
> Date: Thu,  8 Feb 2018 11:59:25 +0800
>
>> We need limit the maximum size of queue, otherwise it may cause
>> several side effects e.g slab will warn when the size exceeds
>> KMALLOC_MAX_SIZE. Using KMALLOC_MAX_SIZE still looks too so this patch
>> tries to limit it to 64K. This value could be revisited if we found a
>> real case that needs more.
>>
>> Reported-by: syzbot+e4d4f9ddd4295539735d@syzkaller.appspotmail.com
>> Fixes: 2e0ab8ca83c12 ("ptr_ring: array based FIFO for pointers")
>> Signed-off-by: Jason Wang <jasowang@redhat.com>
>   ...
>> @@ -466,6 +468,8 @@ 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 > PTR_RING_MAX_ALLOC)
>> +		return NULL;
>>   	return kvmalloc_array(size, sizeof(void *), gfp | __GFP_ZERO);
>>   }
> This doesn't limit the allocation to 64K.  It limits it to 64K * sizeof(void *).

Right, will fix this.

Thanks