linux-kernel - Re: [PATCH] net: sock: validate data_len before allocating skb in sock_alloc_send

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Date:	Thu, 31 May 2012 14:00:14 +0800
From:	Jason Wang <jasowang@...hat.com>
To:	David Miller <davem@...emloft.net>
CC:	eric.dumazet@...il.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	mst@...hat.com
Subject: Re: [PATCH] net: sock: validate data_len before allocating skb in
 sock_alloc_send_pskb()

On 05/30/2012 03:02 PM, David Miller wrote:
> From: Eric Dumazet<eric.dumazet@...il.com>
> Date: Wed, 30 May 2012 08:46:23 +0200
>
>> Why doing this test in the while (1) block, it should be done before the
>> loop...
>>
>> Or even in the caller, note net/unix/af_unix.c does this right.
>>
>>          if (len>  SKB_MAX_ALLOC)
>>                  data_len = min_t(size_t,
>>                                   len - SKB_MAX_ALLOC,
>>                                   MAX_SKB_FRAGS * PAGE_SIZE);
>>
>>          skb = sock_alloc_send_pskb(sk, len - data_len, data_len,
>>                                     msg->msg_flags&  MSG_DONTWAIT,&err);
> My impression is that the callers should be fixed to.  It makes no sense
> to penalize the call sites that get this right.
>
> And yes, if we do check it in sock_alloc_send_pskb() it should be done
> at function entry, not inside the loop.

Sure, so is it ok for me to send a V2 that just do the fixing in 
sock_alloc_sned_pskb() as it's simple and easy to be accepted by stable 
version?

For the fix of callers, I want to post fixes on top as I find there's 
some code duplication of {tun|macvtap|packet}_alloc_skb() and I want to 
unify them to a common helper in sock.c. Then I can fix this issue in 
the new helper.
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