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Subject[PATCH 4.20 130/183] sctp: call gso_reset_checksum when computing checksum in sctp_gso_segment
Date
4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Xin Long <lucien.xin@gmail.com>

[ Upstream commit fc228abc2347e106a44c0e9b29ab70b712c4ca51 ]

Jianlin reported a panic when running sctp gso over gre over vlan device:

[ 84.772930] RIP: 0010:do_csum+0x6d/0x170
[ 84.790605] Call Trace:
[ 84.791054] csum_partial+0xd/0x20
[ 84.791657] gre_gso_segment+0x2c3/0x390
[ 84.792364] inet_gso_segment+0x161/0x3e0
[ 84.793071] skb_mac_gso_segment+0xb8/0x120
[ 84.793846] __skb_gso_segment+0x7e/0x180
[ 84.794581] validate_xmit_skb+0x141/0x2e0
[ 84.795297] __dev_queue_xmit+0x258/0x8f0
[ 84.795949] ? eth_header+0x26/0xc0
[ 84.796581] ip_finish_output2+0x196/0x430
[ 84.797295] ? skb_gso_validate_network_len+0x11/0x80
[ 84.798183] ? ip_finish_output+0x169/0x270
[ 84.798875] ip_output+0x6c/0xe0
[ 84.799413] ? ip_append_data.part.50+0xc0/0xc0
[ 84.800145] iptunnel_xmit+0x144/0x1c0
[ 84.800814] ip_tunnel_xmit+0x62d/0x930 [ip_tunnel]
[ 84.801699] gre_tap_xmit+0xac/0xf0 [ip_gre]
[ 84.802395] dev_hard_start_xmit+0xa5/0x210
[ 84.803086] sch_direct_xmit+0x14f/0x340
[ 84.803733] __dev_queue_xmit+0x799/0x8f0
[ 84.804472] ip_finish_output2+0x2e0/0x430
[ 84.805255] ? skb_gso_validate_network_len+0x11/0x80
[ 84.806154] ip_output+0x6c/0xe0
[ 84.806721] ? ip_append_data.part.50+0xc0/0xc0
[ 84.807516] sctp_packet_transmit+0x716/0xa10 [sctp]
[ 84.808337] sctp_outq_flush+0xd7/0x880 [sctp]

It was caused by SKB_GSO_CB(skb)->csum_start not set in sctp_gso_segment.
sctp_gso_segment() calls skb_segment() with 'feature | NETIF_F_HW_CSUM',
which causes SKB_GSO_CB(skb)->csum_start not to be set in skb_segment().

For TCP/UDP, when feature supports HW_CSUM, CHECKSUM_PARTIAL will be set
and gso_reset_checksum will be called to set SKB_GSO_CB(skb)->csum_start.

So SCTP should do the same as TCP/UDP, to call gso_reset_checksum() when
computing checksum in sctp_gso_segment.

Reported-by: Jianlin Shi <jishi@redhat.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/sctp/offload.c | 1 +
1 file changed, 1 insertion(+)

--- a/net/sctp/offload.c
+++ b/net/sctp/offload.c
@@ -36,6 +36,7 @@ static __le32 sctp_gso_make_checksum(str
{
skb->ip_summed = CHECKSUM_NONE;
skb->csum_not_inet = 0;
+ gso_reset_checksum(skb, ~0);
return sctp_compute_cksum(skb, skb_transport_offset(skb));
}


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