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Subject[PATCH NET v4 5/7] vrf: use skb_expand_head in vrf_finish_output
Date
Unlike skb_realloc_headroom, new helper skb_expand_head
does not allocate a new skb if possible.

Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
---
v4: fixes null pointer dereference reported by Julian Wiedmann,
replace skb->dev by dev = skb_dst(skb)->dev
vrf_finish_output() is only called from vrf_output(),
it set skb->dev to skb_dst(skb)->dev and calls POSTROUTING netfilter
hooks, where output device should not be changed.
---
drivers/net/vrf.c | 23 ++++++++---------------
1 file changed, 8 insertions(+), 15 deletions(-)

diff --git a/drivers/net/vrf.c b/drivers/net/vrf.c
index 2b1b944..168d4ef 100644
--- a/drivers/net/vrf.c
+++ b/drivers/net/vrf.c
@@ -857,30 +857,24 @@ static int vrf_finish_output(struct net *net, struct sock *sk, struct sk_buff *s
unsigned int hh_len = LL_RESERVED_SPACE(dev);
struct neighbour *neigh;
bool is_v6gw = false;
- int ret = -EINVAL;

nf_reset_ct(skb);

/* Be paranoid, rather than too clever. */
if (unlikely(skb_headroom(skb) < hh_len && dev->header_ops)) {
- struct sk_buff *skb2;
-
- skb2 = skb_realloc_headroom(skb, LL_RESERVED_SPACE(dev));
- if (!skb2) {
- ret = -ENOMEM;
- goto err;
+ skb = skb_expand_head(skb, hh_len);
+ if (!skb) {
+ dev->stats.tx_errors++;
+ return -ENOMEM;
}
- if (skb->sk)
- skb_set_owner_w(skb2, skb->sk);
-
- consume_skb(skb);
- skb = skb2;
}

rcu_read_lock_bh();

neigh = ip_neigh_for_gw(rt, skb, &is_v6gw);
if (!IS_ERR(neigh)) {
+ int ret;
+
sock_confirm_neigh(skb, neigh);
/* if crossing protocols, can not use the cached header */
ret = neigh_output(neigh, skb, is_v6gw);
@@ -889,9 +883,8 @@ static int vrf_finish_output(struct net *net, struct sock *sk, struct sk_buff *s
}

rcu_read_unlock_bh();
-err:
- vrf_tx_error(skb->dev, skb);
- return ret;
+ vrf_tx_error(dev, skb);
+ return -EINVAL;
}

static int vrf_output(struct net *net, struct sock *sk, struct sk_buff *skb)
--
1.8.3.1
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