Re: [PATCH] net: Fix potential out of bound write in skb_try_coalesce()

[linmiaohe]

Eric Dumazet <edumazet@xxxxxxxxxx> wrote:
>On Tue, Aug 4, 2020 at 4:46 AM linmiaohe <linmiaohe@xxxxxxxxxx> wrote:
>>
>> From: Miaohe Lin <linmiaohe@xxxxxxxxxx>
>>
>> The head_frag of skb would occupy one extra skb_frag_t. Take it into 
>> account or out of bound write to skb frags may happen.
>>
>
>Please share a stack trace if this was a real bug spotted in the wild.
>
>I do not believe this patch is correct.
>
>if (A + B >= MAX)   is equivalent to  if (A + B + 1 > MAX)
>
>Note how the other condition (when there is no bytes in skb header) is coded :
>
>if (A + B > MAX) return false;
>
>In anycase, please always provide a Fixes: tag for any bug fix.
>
>Thanks.

Many thanks for your patient explaination. I compared (A + B >= MAX) with (A + B + 1 > MAX) in skb_gro_receive(),
but I missed the '='. It's my oversight, I'am really sorry about it.

Thanks again.