CVE-2024-27018 — netfilter: br_netfilter: skip conntrack input hook for promisc packets

Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

netfilter: br_netfilter: skip conntrack input hook for promisc packets

For historical reasons, when bridge device is in promisc mode, packets that are directed to the taps follow bridge input hook path. This patch adds a workaround to reset conntrack for these packets.

Jianbo Liu reports warning splats in their test infrastructure where cloned packets reach the br_netfilter input hook to confirm the conntrack object.

Scratch one bit from BR_INPUT_SKB_CB to annotate that this packet has reached the input hook because it is passed up to the bridge device to reach the taps.

[ 57.571874] WARNING: CPU: 1 PID: 0 at net/bridge/br_netfilter_hooks.c:616 br_nf_local_in+0x157/0x180 [br_netfilter] [ 57.572749] Modules linked in: xt_MASQUERADE nf_conntrack_netlink nfnetlink iptable_nat xt_addrtype xt_conntrack nf_nat br_netfilter rpcsec_gss_krb5 auth_rpcgss oid_registry overlay rpcrdma rdma_ucm ib_iser libiscsi scsi_transport_isc si ib_umad rdma_cm ib_ipoib iw_cm ib_cm mlx5_ib ib_uverbs ib_core mlx5ctl mlx5_core [ 57.575158] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 6.8.0+ #19 [ 57.575700] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 [ 57.576662] RIP: 0010:br_nf_local_in+0x157/0x180 [br_netfilter] [ 57.577195] Code: fe ff ff 41 bd 04 00 00 00 be 04 00 00 00 e9 4a ff ff ff be 04 00 00 00 48 89 ef e8 f3 a9 3c e1 66 83 ad b4 00 00 00 04 eb…

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CVE-2024-27018 — netfilter: br_netfilter: skip conntrack input hook for promisc packets