[PATCH 4.19 51/57] net: geneve: check skb is large enough for IPv4/IPv6 header

From: Greg Kroah-Hartman
Date: Mon Apr 26 2021 - 03:45:33 EST

From: Phillip Potter <phil@xxxxxxxxxxxxxxxx>

[ Upstream commit 6628ddfec7580882f11fdc5c194a8ea781fdadfa ]

Check within geneve_xmit_skb/geneve6_xmit_skb that sk_buff structure
is large enough to include IPv4 or IPv6 header, and reject if not. The
geneve_xmit_skb portion and overall idea was contributed by Eric Dumazet.
Fixes a KMSAN-found uninit-value bug reported by syzbot at:

Suggested-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Reported-by: syzbot+2e406a9ac75bb71d4b7a@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Phillip Potter <phil@xxxxxxxxxxxxxxxx>
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
drivers/net/geneve.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/drivers/net/geneve.c b/drivers/net/geneve.c
index 2e2afc824a6a..ce6fecf421f8 100644
--- a/drivers/net/geneve.c
+++ b/drivers/net/geneve.c
@@ -839,6 +839,9 @@ static int geneve_xmit_skb(struct sk_buff *skb, struct net_device *dev,
__be16 df;
int err;

+ if (!pskb_network_may_pull(skb, sizeof(struct iphdr)))
+ return -EINVAL;
sport = udp_flow_src_port(geneve->net, skb, 1, USHRT_MAX, true);
rt = geneve_get_v4_rt(skb, dev, gs4, &fl4, info,
geneve->info.key.tp_dst, sport);
@@ -882,6 +885,9 @@ static int geneve6_xmit_skb(struct sk_buff *skb, struct net_device *dev,
__be16 sport;
int err;

+ if (!pskb_network_may_pull(skb, sizeof(struct ipv6hdr)))
+ return -EINVAL;
sport = udp_flow_src_port(geneve->net, skb, 1, USHRT_MAX, true);
dst = geneve_get_v6_dst(skb, dev, gs6, &fl6, info,
geneve->info.key.tp_dst, sport);