On Thu, Oct 26, 2017 at 5:15 AM, Jason Wang <[email protected]> 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 <[email protected]> > Cc: Willem de Bruijn <[email protected]> > Cc: Wei Wei <[email protected]> > Cc: Dmitry Vyukov <[email protected]> > Cc: Mark Rutland <[email protected]> > Reported-by: Wei Wei <[email protected]> > Signed-off-by: Jason Wang <[email protected]> > --- > - 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) Then eventually use skb_reserve() for NET_IP_ALIGN, but I guess it is already done.
