+++ /dev/null
-From 6043b794c7668c19dabc4a93c75b924a19474d59 Mon Sep 17 00:00:00 2001
-From: Paul Chaignon <paul.chaignon@gmail.com>
-Date: Thu, 29 May 2025 12:28:05 +0200
-Subject: net: Fix checksum update for ILA adj-transport
-
-From: Paul Chaignon <paul.chaignon@gmail.com>
-
-commit 6043b794c7668c19dabc4a93c75b924a19474d59 upstream.
-
-During ILA address translations, the L4 checksums can be handled in
-different ways. One of them, adj-transport, consist in parsing the
-transport layer and updating any found checksum. This logic relies on
-inet_proto_csum_replace_by_diff and produces an incorrect skb->csum when
-in state CHECKSUM_COMPLETE.
-
-This bug can be reproduced with a simple ILA to SIR mapping, assuming
-packets are received with CHECKSUM_COMPLETE:
-
- $ ip a show dev eth0
- 14: eth0@if15: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
- link/ether 62:ae:35:9e:0f:8d brd ff:ff:ff:ff:ff:ff link-netnsid 0
- inet6 3333:0:0:1::c078/64 scope global
- valid_lft forever preferred_lft forever
- inet6 fd00:10:244:1::c078/128 scope global nodad
- valid_lft forever preferred_lft forever
- inet6 fe80::60ae:35ff:fe9e:f8d/64 scope link proto kernel_ll
- valid_lft forever preferred_lft forever
- $ ip ila add loc_match fd00:10:244:1 loc 3333:0:0:1 \
- csum-mode adj-transport ident-type luid dev eth0
-
-Then I hit [fd00:10:244:1::c078]:8000 with a server listening only on
-[3333:0:0:1::c078]:8000. With the bug, the SYN packet is dropped with
-SKB_DROP_REASON_TCP_CSUM after inet_proto_csum_replace_by_diff changed
-skb->csum. The translation and drop are visible on pwru [1] traces:
-
- IFACE TUPLE FUNC
- eth0:9 [fd00:10:244:3::3d8]:51420->[fd00:10:244:1::c078]:8000(tcp) ipv6_rcv
- eth0:9 [fd00:10:244:3::3d8]:51420->[fd00:10:244:1::c078]:8000(tcp) ip6_rcv_core
- eth0:9 [fd00:10:244:3::3d8]:51420->[fd00:10:244:1::c078]:8000(tcp) nf_hook_slow
- eth0:9 [fd00:10:244:3::3d8]:51420->[fd00:10:244:1::c078]:8000(tcp) inet_proto_csum_replace_by_diff
- eth0:9 [fd00:10:244:3::3d8]:51420->[3333:0:0:1::c078]:8000(tcp) tcp_v6_early_demux
- eth0:9 [fd00:10:244:3::3d8]:51420->[3333:0:0:1::c078]:8000(tcp) ip6_route_input
- eth0:9 [fd00:10:244:3::3d8]:51420->[3333:0:0:1::c078]:8000(tcp) ip6_input
- eth0:9 [fd00:10:244:3::3d8]:51420->[3333:0:0:1::c078]:8000(tcp) ip6_input_finish
- eth0:9 [fd00:10:244:3::3d8]:51420->[3333:0:0:1::c078]:8000(tcp) ip6_protocol_deliver_rcu
- eth0:9 [fd00:10:244:3::3d8]:51420->[3333:0:0:1::c078]:8000(tcp) raw6_local_deliver
- eth0:9 [fd00:10:244:3::3d8]:51420->[3333:0:0:1::c078]:8000(tcp) ipv6_raw_deliver
- eth0:9 [fd00:10:244:3::3d8]:51420->[3333:0:0:1::c078]:8000(tcp) tcp_v6_rcv
- eth0:9 [fd00:10:244:3::3d8]:51420->[3333:0:0:1::c078]:8000(tcp) __skb_checksum_complete
- eth0:9 [fd00:10:244:3::3d8]:51420->[3333:0:0:1::c078]:8000(tcp) kfree_skb_reason(SKB_DROP_REASON_TCP_CSUM)
- eth0:9 [fd00:10:244:3::3d8]:51420->[3333:0:0:1::c078]:8000(tcp) skb_release_head_state
- eth0:9 [fd00:10:244:3::3d8]:51420->[3333:0:0:1::c078]:8000(tcp) skb_release_data
- eth0:9 [fd00:10:244:3::3d8]:51420->[3333:0:0:1::c078]:8000(tcp) skb_free_head
- eth0:9 [fd00:10:244:3::3d8]:51420->[3333:0:0:1::c078]:8000(tcp) kfree_skbmem
-
-This is happening because inet_proto_csum_replace_by_diff is updating
-skb->csum when it shouldn't. The L4 checksum is updated such that it
-"cancels" the IPv6 address change in terms of checksum computation, so
-the impact on skb->csum is null.
-
-Note this would be different for an IPv4 packet since three fields
-would be updated: the IPv4 address, the IP checksum, and the L4
-checksum. Two would cancel each other and skb->csum would still need
-to be updated to take the L4 checksum change into account.
-
-This patch fixes it by passing an ipv6 flag to
-inet_proto_csum_replace_by_diff, to skip the skb->csum update if we're
-in the IPv6 case. Note the behavior of the only other user of
-inet_proto_csum_replace_by_diff, the BPF subsystem, is left as is in
-this patch and fixed in the subsequent patch.
-
-With the fix, using the reproduction from above, I can confirm
-skb->csum is not touched by inet_proto_csum_replace_by_diff and the TCP
-SYN proceeds to the application after the ILA translation.
-
-Link: https://github.com/cilium/pwru [1]
-Fixes: 65d7ab8de582 ("net: Identifier Locator Addressing module")
-Signed-off-by: Paul Chaignon <paul.chaignon@gmail.com>
-Acked-by: Daniel Borkmann <daniel@iogearbox.net>
-Link: https://patch.msgid.link/b5539869e3550d46068504feb02d37653d939c0b.1748509484.git.paul.chaignon@gmail.com
-Signed-off-by: Jakub Kicinski <kuba@kernel.org>
-[ Fixed conflict due to unrelated change in inet_proto_csum_replace_by_diff. ]
-Signed-off-by: Paul Chaignon <paul.chaignon@gmail.com>
-Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
----
- include/net/checksum.h | 2 +-
- net/core/filter.c | 2 +-
- net/core/utils.c | 4 ++--
- net/ipv6/ila/ila_common.c | 6 +++---
- 4 files changed, 7 insertions(+), 7 deletions(-)
-
---- a/include/net/checksum.h
-+++ b/include/net/checksum.h
-@@ -152,7 +152,7 @@ void inet_proto_csum_replace16(__sum16 *
- const __be32 *from, const __be32 *to,
- bool pseudohdr);
- void inet_proto_csum_replace_by_diff(__sum16 *sum, struct sk_buff *skb,
-- __wsum diff, bool pseudohdr);
-+ __wsum diff, bool pseudohdr, bool ipv6);
-
- static __always_inline
- void inet_proto_csum_replace2(__sum16 *sum, struct sk_buff *skb,
---- a/net/core/filter.c
-+++ b/net/core/filter.c
-@@ -1949,7 +1949,7 @@ BPF_CALL_5(bpf_l4_csum_replace, struct s
- if (unlikely(from != 0))
- return -EINVAL;
-
-- inet_proto_csum_replace_by_diff(ptr, skb, to, is_pseudo);
-+ inet_proto_csum_replace_by_diff(ptr, skb, to, is_pseudo, false);
- break;
- case 2:
- inet_proto_csum_replace2(ptr, skb, from, to, is_pseudo);
---- a/net/core/utils.c
-+++ b/net/core/utils.c
-@@ -473,11 +473,11 @@ void inet_proto_csum_replace16(__sum16 *
- EXPORT_SYMBOL(inet_proto_csum_replace16);
-
- void inet_proto_csum_replace_by_diff(__sum16 *sum, struct sk_buff *skb,
-- __wsum diff, bool pseudohdr)
-+ __wsum diff, bool pseudohdr, bool ipv6)
- {
- if (skb->ip_summed != CHECKSUM_PARTIAL) {
- *sum = csum_fold(csum_add(diff, ~csum_unfold(*sum)));
-- if (skb->ip_summed == CHECKSUM_COMPLETE && pseudohdr)
-+ if (skb->ip_summed == CHECKSUM_COMPLETE && pseudohdr && !ipv6)
- skb->csum = ~csum_add(diff, ~skb->csum);
- } else if (pseudohdr) {
- *sum = ~csum_fold(csum_add(diff, csum_unfold(*sum)));
---- a/net/ipv6/ila/ila_common.c
-+++ b/net/ipv6/ila/ila_common.c
-@@ -86,7 +86,7 @@ static void ila_csum_adjust_transport(st
-
- diff = get_csum_diff(ip6h, p);
- inet_proto_csum_replace_by_diff(&th->check, skb,
-- diff, true);
-+ diff, true, true);
- }
- break;
- case NEXTHDR_UDP:
-@@ -97,7 +97,7 @@ static void ila_csum_adjust_transport(st
- if (uh->check || skb->ip_summed == CHECKSUM_PARTIAL) {
- diff = get_csum_diff(ip6h, p);
- inet_proto_csum_replace_by_diff(&uh->check, skb,
-- diff, true);
-+ diff, true, true);
- if (!uh->check)
- uh->check = CSUM_MANGLED_0;
- }
-@@ -111,7 +111,7 @@ static void ila_csum_adjust_transport(st
-
- diff = get_csum_diff(ip6h, p);
- inet_proto_csum_replace_by_diff(&ih->icmp6_cksum, skb,
-- diff, true);
-+ diff, true, true);
- }
- break;
- }
projects / thirdparty / kernel / stable-queue.git / commitdiff
