On Tue, Jul 09, 2013 at 06:10:50PM +0800, Jason Wang wrote: > Userspace may produce vectors greater than MAX_SKB_FRAGS. When we try to > linearize parts of the skb to let the rest of iov to be fit in > the frags, we need count copylen into linear when calling tun_alloc_skb() > instead of partly counting it into data_len. Since this breaks > zerocopy_sg_from_iovec() since its inner counter assumes nr_frags should > be zero at beginning. This cause nr_frags to be increased wrongly without > setting the correct frags. > > This bug were introduced from 0690899b4d4501b3505be069b9a687e68ccbe15b > (tun: experimental zero copy tx support) > > Cc: Michael S. Tsirkin <[email protected]> > Signed-off-by: Jason Wang <[email protected]> > --- > This patch is needed for stable. > --- > drivers/net/tun.c | 3 ++- > 1 files changed, 2 insertions(+), 1 deletions(-) > > diff --git a/drivers/net/tun.c b/drivers/net/tun.c > index 7eab5fc..01d5a86 100644 > --- a/drivers/net/tun.c > +++ b/drivers/net/tun.c > @@ -1109,7 +1109,8 @@ static ssize_t tun_get_user(struct tun_struct *tun, > struct tun_file *tfile, > } else > copylen = len; > > - skb = tun_alloc_skb(tfile, align, copylen, gso.hdr_len, noblock); > + skb = tun_alloc_skb(tfile, align, copylen, > + zerocopy ? copylen : gso.hdr_len, noblock); > if (IS_ERR(skb)) { > if (PTR_ERR(skb) != -EAGAIN) > tun->dev->stats.rx_dropped++;
Good catch, thanks. But let's add a new variable and set it in the if statement above instead of an extra branch here - not for performance but because it's clearer this way. > -- > 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
