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Subject[PATCH 5.4 115/142] xfrm: call xfrm_output_gso when inner_protocol is set in xfrm_output
Date
From: Xin Long <lucien.xin@gmail.com>

commit a204aef9fd77dce1efd9066ca4e44eede99cd858 upstream.

An use-after-free crash can be triggered when sending big packets over
vxlan over esp with esp offload enabled:

[] BUG: KASAN: use-after-free in ipv6_gso_pull_exthdrs.part.8+0x32c/0x4e0
[] Call Trace:
[] dump_stack+0x75/0xa0
[] kasan_report+0x37/0x50
[] ipv6_gso_pull_exthdrs.part.8+0x32c/0x4e0
[] ipv6_gso_segment+0x2c8/0x13c0
[] skb_mac_gso_segment+0x1cb/0x420
[] skb_udp_tunnel_segment+0x6b5/0x1c90
[] inet_gso_segment+0x440/0x1380
[] skb_mac_gso_segment+0x1cb/0x420
[] esp4_gso_segment+0xae8/0x1709 [esp4_offload]
[] inet_gso_segment+0x440/0x1380
[] skb_mac_gso_segment+0x1cb/0x420
[] __skb_gso_segment+0x2d7/0x5f0
[] validate_xmit_skb+0x527/0xb10
[] __dev_queue_xmit+0x10f8/0x2320 <---
[] ip_finish_output2+0xa2e/0x1b50
[] ip_output+0x1a8/0x2f0
[] xfrm_output_resume+0x110e/0x15f0
[] __xfrm4_output+0xe1/0x1b0
[] xfrm4_output+0xa0/0x200
[] iptunnel_xmit+0x5a7/0x920
[] vxlan_xmit_one+0x1658/0x37a0 [vxlan]
[] vxlan_xmit+0x5e4/0x3ec8 [vxlan]
[] dev_hard_start_xmit+0x125/0x540
[] __dev_queue_xmit+0x17bd/0x2320 <---
[] ip6_finish_output2+0xb20/0x1b80
[] ip6_output+0x1b3/0x390
[] ip6_xmit+0xb82/0x17e0
[] inet6_csk_xmit+0x225/0x3d0
[] __tcp_transmit_skb+0x1763/0x3520
[] tcp_write_xmit+0xd64/0x5fe0
[] __tcp_push_pending_frames+0x8c/0x320
[] tcp_sendmsg_locked+0x2245/0x3500
[] tcp_sendmsg+0x27/0x40

As on the tx path of vxlan over esp, skb->inner_network_header would be
set on vxlan_xmit() and xfrm4_tunnel_encap_add(), and the later one can
overwrite the former one. It causes skb_udp_tunnel_segment() to use a
wrong skb->inner_network_header, then the issue occurs.

This patch is to fix it by calling xfrm_output_gso() instead when the
inner_protocol is set, in which gso_segment of inner_protocol will be
done first.

While at it, also improve some code around.

Fixes: 7862b4058b9f ("esp: Add gso handlers for esp4 and esp6")
Reported-by: Xiumei Mu <xmu@redhat.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
net/xfrm/xfrm_output.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)

--- a/net/xfrm/xfrm_output.c
+++ b/net/xfrm/xfrm_output.c
@@ -586,18 +586,20 @@ int xfrm_output(struct sock *sk, struct
xfrm_state_hold(x);

if (skb_is_gso(skb)) {
- skb_shinfo(skb)->gso_type |= SKB_GSO_ESP;
+ if (skb->inner_protocol)
+ return xfrm_output_gso(net, sk, skb);

- return xfrm_output2(net, sk, skb);
+ skb_shinfo(skb)->gso_type |= SKB_GSO_ESP;
+ goto out;
}

if (x->xso.dev && x->xso.dev->features & NETIF_F_HW_ESP_TX_CSUM)
goto out;
+ } else {
+ if (skb_is_gso(skb))
+ return xfrm_output_gso(net, sk, skb);
}

- if (skb_is_gso(skb))
- return xfrm_output_gso(net, sk, skb);
-
if (skb->ip_summed == CHECKSUM_PARTIAL) {
err = skb_checksum_help(skb);
if (err) {

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