[PATCH 5.10 040/145] bareudp: Fix use of incorrect min_headroom size

Greg Kroah-Hartman
2021-01-11T13:15:23Z

From: Taehee Yoo <ap420073@gmail.com>

[ Upstream commit 10ad3e998fa0c25315f27cf3002ff8b02dc31c38 ]

In the bareudp6_xmit_skb(), it calculates min_headroom.
At that point, it uses struct iphdr, but it's not correct.
So panic could occur.
The struct ipv6hdr should be used.

Test commands:
ip netns add A
ip netns add B
ip link add veth0 netns A type veth peer name veth1 netns B
ip netns exec A ip link set veth0 up
ip netns exec A ip a a 2001:db8:0::1/64 dev veth0
ip netns exec B ip link set veth1 up
ip netns exec B ip a a 2001:db8:0::2/64 dev veth1

for i in {10..1}
do
let A=$i-1
ip netns exec A ip link add bareudp$i type bareudp dstport $i \
ethertype 0x86dd
ip netns exec A ip link set bareudp$i up
ip netns exec A ip -6 a a 2001:db8:$i::1/64 dev bareudp$i
ip netns exec A ip -6 r a 2001:db8:$i::2 encap ip6 src \
2001:db8:$A::1 dst 2001:db8:$A::2 via 2001:db8:$i::2 \
dev bareudp$i

ip netns exec B ip link add bareudp$i type bareudp dstport $i \
ethertype 0x86dd
ip netns exec B ip link set bareudp$i up
ip netns exec B ip -6 a a 2001:db8:$i::2/64 dev bareudp$i
ip netns exec B ip -6 r a 2001:db8:$i::1 encap ip6 src \
2001:db8:$A::2 dst 2001:db8:$A::1 via 2001:db8:$i::1 \
dev bareudp$i
done
ip netns exec A ping 2001:db8:7::2

Splat looks like:
[ 66.436679][ C2] skbuff: skb_under_panic: text:ffffffff928614c8 len:454 put:14 head:ffff88810abb4000 data:ffff88810abb3ffa tail:0x1c0 end:0x3ec0 dev:veth0
[ 66.441626][ C2] ------------[ cut here ]------------
[ 66.443458][ C2] kernel BUG at net/core/skbuff.c:109!
[ 66.445313][ C2] invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN PTI
[ 66.447606][ C2] CPU: 2 PID: 913 Comm: ping Not tainted 5.10.0+ #819
[ 66.450251][ C2] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014
[ 66.453713][ C2] RIP: 0010:skb_panic+0x15d/0x15f
[ 66.455345][ C2] Code: 98 fe 4c 8b 4c 24 10 53 8b 4d 70 45 89 e0 48 c7 c7 60 8b 78 93 41 57 41 56 41 55 48 8b 54 24 20 48 8b 74 24 28 e8 b5 40 f9 ff <0f> 0b 48 8b 6c 24 20 89 34 24 e8 08 c9 98 fe 8b 34 24 48 c7 c1 80
[ 66.462314][ C2] RSP: 0018:ffff888119209648 EFLAGS: 00010286
[ 66.464281][ C2] RAX: 0000000000000089 RBX: ffff888003159000 RCX: 0000000000000000
[ 66.467216][ C2] RDX: 0000000000000089 RSI: 0000000000000008 RDI: ffffed10232412c0
[ 66.469768][ C2] RBP: ffff88810a53d440 R08: ffffed102328018d R09: ffffed102328018d
[ 66.472297][ C2] R10: ffff888119400c67 R11: ffffed102328018c R12: 000000000000000e
[ 66.474833][ C2] R13: ffff88810abb3ffa R14: 00000000000001c0 R15: 0000000000003ec0
[ 66.477361][ C2] FS: 00007f37c0c72f00(0000) GS:ffff888119200000(0000) knlGS:0000000000000000
[ 66.480214][ C2] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 66.482296][ C2] CR2: 000055a058808570 CR3: 000000011039e002 CR4: 00000000003706e0
[ 66.484811][ C2] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 66.487793][ C2] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 66.490424][ C2] Call Trace:
[ 66.491469][ C2] <IRQ>
[ 66.492374][ C2] ? eth_header+0x28/0x190
[ 66.494054][ C2] ? eth_header+0x28/0x190
[ 66.495401][ C2] skb_push.cold.99+0x22/0x22
[ 66.496700][ C2] eth_header+0x28/0x190
[ 66.497867][ C2] neigh_resolve_output+0x3de/0x720
[ 66.499615][ C2] ? __neigh_update+0x7e8/0x20a0
[ 66.501176][ C2] __neigh_update+0x8bd/0x20a0
[ 66.502749][ C2] ndisc_update+0x34/0xc0
[ 66.504010][ C2] ndisc_recv_na+0x8da/0xb80
[ 66.505041][ C2] ? pndisc_redo+0x20/0x20
[ 66.505888][ C2] ? rcu_read_lock_sched_held+0xc0/0xc0
[ 66.506965][ C2] ndisc_rcv+0x3a0/0x470
[ 66.507797][ C2] icmpv6_rcv+0xad9/0x1b00
[ 66.508645][ C2] ip6_protocol_deliver_rcu+0xcd6/0x1560
[ 66.509719][ C2] ip6_input_finish+0x5b/0xf0
[ 66.510615][ C2] ip6_input+0xcd/0x2d0
[ 66.511406][ C2] ? ip6_input_finish+0xf0/0xf0
[ 66.512327][ C2] ? rcu_read_lock_held+0x91/0xa0
[ 66.513279][ C2] ? ip6_protocol_deliver_rcu+0x1560/0x1560
[ 66.514414][ C2] ipv6_rcv+0xe8/0x300
[ ... ]

Acked-by: Guillaume Nault <gnault@redhat.com>
Fixes: 571912c69f0e ("net: UDP tunnel encapsulation module for tunnelling different protocols like MPLS, IP, NSH etc.")
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Link: https://lore.kernel.org/r/20201228152146.24270-1-ap420073@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/bareudp.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/net/bareudp.c
+++ b/drivers/net/bareudp.c
@@ -380,7 +380,7 @@ static int bareudp6_xmit_skb(struct sk_b
goto free_dst;

min_headroom = LL_RESERVED_SPACE(dst->dev) + dst->header_len +
- BAREUDP_BASE_HLEN + info->options_len + sizeof(struct iphdr);
+ BAREUDP_BASE_HLEN + info->options_len + sizeof(struct ipv6hdr);

err = skb_cow_head(skb, min_headroom);
if (unlikely(err))