4.9-stable review patch. If anyone has any objections, please let me know.
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From: Willem de Bruijn willemb@google.com
[ Upstream commit 9aad13b087ab0a588cd68259de618f100053360e ]
Commit b84bbaf7a6c8 ("packet: in packet_snd start writing at link layer allocation") ensures that packet_snd always starts writing the link layer header in reserved headroom allocated for this purpose.
This is needed because packets may be shorter than hard_header_len, in which case the space up to hard_header_len may be zeroed. But that necessary padding is not accounted for in skb->len.
The fix, however, is buggy. It calls skb_push, which grows skb->len when moving skb->data back. But in this case packet length should not change.
Instead, call skb_reserve, which moves both skb->data and skb->tail back, without changing length.
Fixes: b84bbaf7a6c8 ("packet: in packet_snd start writing at link layer allocation") Reported-by: Tariq Toukan tariqt@mellanox.com Signed-off-by: Willem de Bruijn willemb@google.com Acked-by: Soheil Hassas Yeganeh soheil@google.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/packet/af_packet.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -2918,7 +2918,7 @@ static int packet_snd(struct socket *soc if (unlikely(offset < 0)) goto out_free; } else if (reserve) { - skb_push(skb, reserve); + skb_reserve(skb, -reserve); }
/* Returns -EFAULT on error */