From: Eric Dumazet I added skb_vlan_inet_prepare() helper in the cited commit, hinting that we would need to use it more broadly. syzbot confirmed this was the case in ip6_gre. uninit-value in ip6table_mangle_hook+0x97d/0x9c0 net/ipv6/netfilter/ip6table_mangle.c:72 ip6t_mangle_out net/ipv6/netfilter/ip6table_mangle.c:56 [inline] ip6table_mangle_hook+0x97d/0x9c0 net/ipv6/netfilter/ip6table_mangle.c:72 nf_hook_entry_hookfn include/linux/netfilter.h:154 [inline] nf_hook_slow+0xf4/0x400 net/netfilter/core.c:626 nf_hook include/linux/netfilter.h:269 [inline] __ip6_local_out+0x5ac/0x640 net/ipv6/output_core.c:143 ip6_local_out+0x4c/0x210 net/ipv6/output_core.c:153 ip6tunnel_xmit+0x129/0x460 include/net/ip6_tunnel.h:161 ip6_tnl_xmit+0x341a/0x3860 net/ipv6/ip6_tunnel.c:1281 Uninit was stored to memory at: ip6_tnl_xmit+0x34f7/0x3860 net/ipv6/ip6_tunnel.c:1277 __gre6_xmit+0x14b9/0x1550 net/ipv6/ip6_gre.c:815 ip6gre_xmit_ipv4 net/ipv6/ip6_gre.c:839 [inline] ip6gre_tunnel_xmit+0x18f7/0x2030 net/ipv6/ip6_gre.c:922 Uninit was created at: slab_post_alloc_hook mm/slub.c:4091 [inline] slab_alloc_node mm/slub.c:4134 [inline] __do_kmalloc_node mm/slub.c:4263 [inline] __kmalloc_node_track_caller_noprof+0x6c7/0xf90 mm/slub.c:4283 kmalloc_reserve+0x23e/0x4a0 net/core/skbuff.c:609 pskb_expand_head+0x226/0x1a60 net/core/skbuff.c:2275 skb_realloc_headroom+0x140/0x2b0 net/core/skbuff.c:2355 ip6_tnl_xmit+0x2106/0x3860 net/ipv6/ip6_tunnel.c:1227 __gre6_xmit+0x14b9/0x1550 net/ipv6/ip6_gre.c:815 ip6gre_xmit_ipv4 net/ipv6/ip6_gre.c:839 [inline] ip6gre_tunnel_xmit+0x18f7/0x2030 net/ipv6/ip6_gre.c:922 Fixes: d8a6213d70ac ("geneve: fix header validation in geneve[6]_xmit_skb") Reported-by: syzbot+6023ea32e206eef7920a@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=6023ea32e206eef7920a Signed-off-by: Eric Dumazet Cc: Mazin Al Haddad Signed-off-by: Florian Westphal --- v3: pass 'true' argument to skb_vlan_inet_prepare to not change network header offset. net/ipv6/ip6_gre.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c index d19d86ed4376..9e214c355e6c 100644 --- a/net/ipv6/ip6_gre.c +++ b/net/ipv6/ip6_gre.c @@ -881,7 +881,7 @@ static netdev_tx_t ip6gre_tunnel_xmit(struct sk_buff *skb, __be16 payload_protocol; int ret; - if (!pskb_inet_may_pull(skb)) + if (skb_vlan_inet_prepare(skb, true)) goto tx_err; if (!ip6_tnl_xmit_ctl(t, &t->parms.laddr, &t->parms.raddr)) @@ -929,7 +929,7 @@ static netdev_tx_t ip6erspan_tunnel_xmit(struct sk_buff *skb, __u32 mtu; int nhoff; - if (!pskb_inet_may_pull(skb)) + if (skb_vlan_inet_prepare(skb, true)) goto tx_err; if (!ip6_tnl_xmit_ctl(t, &t->parms.laddr, &t->parms.raddr)) -- 2.52.0