[PATCH 09/11] esp: Fix GRO when the headers not fully in the linear part of the skb.

[Steffen Klassert <steffen.klassert@secunet.com>]

The GRO layer does not necessarily pull the complete headers
into the linear part of the skb, a part may remain on the
first page fragment. This can lead to a crash if we try to
pull the headers, so make sure we have them on the linear
part before pulling.

Fixes: 7785bba299a8 ("esp: Add a software GRO codepath")
Reported-by: syzbot+82bbd65569c49c6c0c4d@syzkaller.appspotmail.com
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
---
 net/ipv4/esp4_offload.c | 3 ++-
 net/ipv6/esp6_offload.c | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/esp4_offload.c b/net/ipv4/esp4_offload.c
index f8b918c766b0..b1338e576d00 100644
--- a/net/ipv4/esp4_offload.c
+++ b/net/ipv4/esp4_offload.c
@@ -38,7 +38,8 @@ static struct sk_buff **esp4_gro_receive(struct sk_buff **head,
 	__be32 spi;
 	int err;
 
-	skb_pull(skb, offset);
+	if (!pskb_pull(skb, offset))
+		return NULL;
 
 	if ((err = xfrm_parse_spi(skb, IPPROTO_ESP, &spi, &seq)) != 0)
 		goto out;
diff --git a/net/ipv6/esp6_offload.c b/net/ipv6/esp6_offload.c
index 333a478aa161..dd9627490c7c 100644
--- a/net/ipv6/esp6_offload.c
+++ b/net/ipv6/esp6_offload.c
@@ -60,7 +60,8 @@ static struct sk_buff **esp6_gro_receive(struct sk_buff **head,
 	int nhoff;
 	int err;
 
-	skb_pull(skb, offset);
+	if (!pskb_pull(skb, offset))
+		return NULL;
 
 	if ((err = xfrm_parse_spi(skb, IPPROTO_ESP, &spi, &seq)) != 0)
 		goto out;
-- 
2.14.1