From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AC5B12FA65D; Tue, 17 Jun 2025 16:49:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750178971; cv=none; b=dhjlpELrs4L4EAhBB+JxsOizQQrzOzdIUwyPrnNOciK7EBgqvCax7tURhf4NkdHpZRRw47JoeWrcALKL6SSq6zs2w8UsLCJXLZRJNDC2Sdi7XEx3y9NabAuJlE2Xe7vVGvqag596uOCxvwehYl4qtHb+5Cs7lXtFTNDmwwndCN4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750178971; c=relaxed/simple; bh=6606mQYbC17H9PL1cE/rOjGbEjhS/105n3VfS2otA9g=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=IbDSjiapC4GLOGlppvSknNQVo2vxeO11Q1sAHzzVgoZBBd0VO5L8KqfeXx06nKlVqrF0YUmW7dAJxOFw0YueRu9Uh3Qz8n9ckjtsr/aPWZXKOseI78brollB2+ntJoGG3M3TpLjFUvZkVPmWl8JhQNG1hp5edWbOg8KnYgPXaB4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=aGc+4W6d; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="aGc+4W6d" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1E4C1C4CEE7; Tue, 17 Jun 2025 16:49:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1750178971; bh=6606mQYbC17H9PL1cE/rOjGbEjhS/105n3VfS2otA9g=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=aGc+4W6dQkddT+EV0APK2ACYrjPtztSbZwPy9agSJk12qVzZjuZtDwkgNIC59Qyou Z2vtaZlgmPGNni5bNGMRb7Iv9hOjUTQ6UVIAR2Oi76PslCj2wq5jv4/YhzQ7rbSJ/b i9Q8FZZ1Klllezgz8960TfA3pKNyqNjcelXaY0mM= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Paul Chaignon , Daniel Borkmann , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.15 579/780] net: Fix checksum update for ILA adj-transport Date: Tue, 17 Jun 2025 17:24:47 +0200 Message-ID: <20250617152515.063247026@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250617152451.485330293@linuxfoundation.org> References: <20250617152451.485330293@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Paul Chaignon [ Upstream commit 6043b794c7668c19dabc4a93c75b924a19474d59 ] 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: 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 Acked-by: Daniel Borkmann Link: https://patch.msgid.link/b5539869e3550d46068504feb02d37653d939c0b.1748509484.git.paul.chaignon@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- 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(-) diff --git a/include/net/checksum.h b/include/net/checksum.h index 243f972267b8d..be9356d4b67a1 100644 --- a/include/net/checksum.h +++ b/include/net/checksum.h @@ -164,7 +164,7 @@ void inet_proto_csum_replace16(__sum16 *sum, struct sk_buff *skb, 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, diff --git a/net/core/filter.c b/net/core/filter.c index 577a4504e26fa..3c93765742c9c 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -1987,7 +1987,7 @@ BPF_CALL_5(bpf_l4_csum_replace, struct sk_buff *, skb, u32, offset, 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); diff --git a/net/core/utils.c b/net/core/utils.c index 27f4cffaae05d..b8c21a859e27b 100644 --- a/net/core/utils.c +++ b/net/core/utils.c @@ -473,11 +473,11 @@ void inet_proto_csum_replace16(__sum16 *sum, struct sk_buff *skb, 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) { csum_replace_by_diff(sum, diff); - if (skb->ip_summed == CHECKSUM_COMPLETE && pseudohdr) + if (skb->ip_summed == CHECKSUM_COMPLETE && pseudohdr && !ipv6) skb->csum = ~csum_sub(diff, skb->csum); } else if (pseudohdr) { *sum = ~csum_fold(csum_add(diff, csum_unfold(*sum))); diff --git a/net/ipv6/ila/ila_common.c b/net/ipv6/ila/ila_common.c index 95e9146918cc6..b8d43ed4689db 100644 --- a/net/ipv6/ila/ila_common.c +++ b/net/ipv6/ila/ila_common.c @@ -86,7 +86,7 @@ static void ila_csum_adjust_transport(struct sk_buff *skb, 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(struct sk_buff *skb, 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(struct sk_buff *skb, diff = get_csum_diff(ip6h, p); inet_proto_csum_replace_by_diff(&ih->icmp6_cksum, skb, - diff, true); + diff, true, true); } break; } -- 2.39.5