gre: refetch erspan header from skb->data after pskb_may_pull()

After pskb_may_pull() we should always refetch the header
pointers from the skb->data in case it got reallocated.

In gre_parse_header(), the erspan header is still fetched
from the 'options' pointer which is fetched before
pskb_may_pull().

Found this during code review of a KMSAN bug report.

Fixes: cb73ee40b1 ("net: ip_gre: use erspan key field for tunnel lookup")
Cc: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Acked-by: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Acked-by: William Tu <u9012063@gmail.com>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Cong Wang 2019-12-05 19:39:02 -08:00 committed by David S. Miller
parent 02a896ca84
commit 0e4940928c

View file

@ -127,7 +127,7 @@ int gre_parse_header(struct sk_buff *skb, struct tnl_ptk_info *tpi,
if (!pskb_may_pull(skb, nhs + hdr_len + sizeof(*ershdr)))
return -EINVAL;
ershdr = (struct erspan_base_hdr *)options;
ershdr = (struct erspan_base_hdr *)(skb->data + nhs + hdr_len);
tpi->key = cpu_to_be32(get_session_id(ershdr));
}