Messages in this thread | | | Subject | Re: [PATCH net] tuntap: properly align skb->head before building skb | From | Jason Wang <> | Date | Fri, 27 Oct 2017 11:03:57 +0800 |
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On 2017年10月26日 22:11, Eric Dumazet wrote: > On Thu, Oct 26, 2017 at 5:15 AM, Jason Wang <jasowang@redhat.com> wrote: >> An unaligned alloc_frag->offset caused by previous allocation will >> result an unaligned skb->head. This will lead unaligned >> skb_shared_info and then unaligned dataref which requires to be >> aligned for accessing on some architecture. Fix this by aligning >> alloc_frag->offset before the frag refilling. >> >> Fixes: 0bbd7dad34f8 ("tun: make tun_build_skb() thread safe") >> Cc: Eric Dumazet <edumazet@google.com> >> Cc: Willem de Bruijn <willemdebruijn.kernel@gmail.com> >> Cc: Wei Wei <dotweiba@gmail.com> >> Cc: Dmitry Vyukov <dvyukov@google.com> >> Cc: Mark Rutland <mark.rutland@arm.com> >> Reported-by: Wei Wei <dotweiba@gmail.com> >> Signed-off-by: Jason Wang <jasowang@redhat.com> >> --- >> - The patch is needed for -stable. >> - Wei, can you try this patch to see if it solves your issue? >> --- >> drivers/net/tun.c | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/drivers/net/tun.c b/drivers/net/tun.c >> index b9973fb..60e44f2 100644 >> --- a/drivers/net/tun.c >> +++ b/drivers/net/tun.c >> @@ -1286,6 +1286,7 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun, >> buflen += SKB_DATA_ALIGN(len + pad); >> rcu_read_unlock(); >> >> + alloc_frag->offset = ALIGN((u64)alloc_frag->offset, TUN_RX_PAD); > You have to align to one cache line (SMP_CACHE_BYTES), or SKB_DATA_ALIGN(1)
Oh right.
> Then eventually use skb_reserve() for NET_IP_ALIGN, but I guess it is > already done.
Yes.
Thanks
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