* skb allocation size question
@ 2010-09-01 18:51 Aaron Williams
2010-09-01 19:04 ` Eric Dumazet
0 siblings, 1 reply; 2+ messages in thread
From: Aaron Williams @ 2010-09-01 18:51 UTC (permalink / raw)
To: netdev
Hi,
I have been trying to track down an issue in one of our drivers with SKB
allocation and in my research I came across something that seems a bit
strange. In __alloc_skb, a block for the data allocates size + sizeof(struct
skb_shared_info) bytes, yet skb->truesize is set to size + sizeof(struct
sk_buff). Is there a reason for this discrepancy?
-Aaron Williams
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: skb allocation size question
2010-09-01 18:51 skb allocation size question Aaron Williams
@ 2010-09-01 19:04 ` Eric Dumazet
0 siblings, 0 replies; 2+ messages in thread
From: Eric Dumazet @ 2010-09-01 19:04 UTC (permalink / raw)
To: Aaron Williams; +Cc: netdev
Le mercredi 01 septembre 2010 à 11:51 -0700, Aaron Williams a écrit :
> Hi,
>
> I have been trying to track down an issue in one of our drivers with SKB
> allocation and in my research I came across something that seems a bit
> strange. In __alloc_skb, a block for the data allocates size + sizeof(struct
> skb_shared_info) bytes, yet skb->truesize is set to size + sizeof(struct
> sk_buff). Is there a reason for this discrepancy?
Hi Aaron
Not really. We also could add in truesize the sizeof(struct
skb_shared_info).
Including sizeof(struct sk_buff) is enough to prevent a malicious user
filling kernel memory with skb of one byte of payload.
Problem is, adding this extra overhead could slowdown some applications,
using too small RCVBUF / SNDBUF settings.
^ permalink raw reply [flat|nested] 2+ messages in thread
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