Message-ID: <2025052004-CVE-2025-37959-1d15@gregkh>
Date: Tue, 20 May 2025 18:02:13 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-37959: bpf: Scrub packet on bpf_redirect_peer

From: Greg Kroah-Hartman <gregkh@...nel.org>

Description
===========

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

bpf: Scrub packet on bpf_redirect_peer

When bpf_redirect_peer is used to redirect packets to a device in
another network namespace, the skb isn't scrubbed. That can lead skb
information from one namespace to be "misused" in another namespace.

As one example, this is causing Cilium to drop traffic when using
bpf_redirect_peer to redirect packets that just went through IPsec
decryption to a container namespace. The following pwru trace shows (1)
the packet path from the host's XFRM layer to the container's XFRM
layer where it's dropped and (2) the number of active skb extensions at
each function.

    NETNS       MARK  IFACE  TUPLE                                FUNC
    4026533547  d00   eth0   10.244.3.124:35473->10.244.2.158:53  xfrm_rcv_cb
                             .active_extensions = (__u8)2,
    4026533547  d00   eth0   10.244.3.124:35473->10.244.2.158:53  xfrm4_rcv_cb
                             .active_extensions = (__u8)2,
    4026533547  d00   eth0   10.244.3.124:35473->10.244.2.158:53  gro_cells_receive
                             .active_extensions = (__u8)2,
    [...]
    4026533547  0     eth0   10.244.3.124:35473->10.244.2.158:53  skb_do_redirect
                             .active_extensions = (__u8)2,
    4026534999  0     eth0   10.244.3.124:35473->10.244.2.158:53  ip_rcv
                             .active_extensions = (__u8)2,
    4026534999  0     eth0   10.244.3.124:35473->10.244.2.158:53  ip_rcv_core
                             .active_extensions = (__u8)2,
    [...]
    4026534999  0     eth0   10.244.3.124:35473->10.244.2.158:53  udp_queue_rcv_one_skb
                             .active_extensions = (__u8)2,
    4026534999  0     eth0   10.244.3.124:35473->10.244.2.158:53  __xfrm_policy_check
                             .active_extensions = (__u8)2,
    4026534999  0     eth0   10.244.3.124:35473->10.244.2.158:53  __xfrm_decode_session
                             .active_extensions = (__u8)2,
    4026534999  0     eth0   10.244.3.124:35473->10.244.2.158:53  security_xfrm_decode_session
                             .active_extensions = (__u8)2,
    4026534999  0     eth0   10.244.3.124:35473->10.244.2.158:53  kfree_skb_reason(SKB_DROP_REASON_XFRM_POLICY)
                             .active_extensions = (__u8)2,

In this case, there are no XFRM policies in the container's network
namespace so the drop is unexpected. When we decrypt the IPsec packet,
the XFRM state used for decryption is set in the skb extensions. This
information is preserved across the netns switch. When we reach the
XFRM policy check in the container's netns, __xfrm_policy_check drops
the packet with LINUX_MIB_XFRMINNOPOLS because a (container-side) XFRM
policy can't be found that matches the (host-side) XFRM state used for
decryption.

This patch fixes this by scrubbing the packet when using
bpf_redirect_peer, as is done on typical netns switches via veth
devices except skb->mark and skb->tstamp are not zeroed.

The Linux kernel CVE team has assigned CVE-2025-37959 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 5.10 with commit 9aa1206e8f48222f35a0c809f33b2f4aaa1e2661 and fixed in 6.1.139 with commit de1067cc8cf0e8c11ae20cbe5c467aef19d04ded
	Issue introduced in 5.10 with commit 9aa1206e8f48222f35a0c809f33b2f4aaa1e2661 and fixed in 6.6.91 with commit 355b0526336c0bf2bf7feaca033568ede524f763
	Issue introduced in 5.10 with commit 9aa1206e8f48222f35a0c809f33b2f4aaa1e2661 and fixed in 6.12.29 with commit b37e54259cab4f78b53953d6f6268b85f07bef3e
	Issue introduced in 5.10 with commit 9aa1206e8f48222f35a0c809f33b2f4aaa1e2661 and fixed in 6.14.7 with commit 9e15ef33ba39fb6d9d1f51445957f16983a9437a
	Issue introduced in 5.10 with commit 9aa1206e8f48222f35a0c809f33b2f4aaa1e2661 and fixed in 6.15-rc6 with commit c4327229948879814229b46aa26a750718888503

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2025-37959
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	net/core/filter.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/de1067cc8cf0e8c11ae20cbe5c467aef19d04ded
	https://git.kernel.org/stable/c/355b0526336c0bf2bf7feaca033568ede524f763
	https://git.kernel.org/stable/c/b37e54259cab4f78b53953d6f6268b85f07bef3e
	https://git.kernel.org/stable/c/9e15ef33ba39fb6d9d1f51445957f16983a9437a
	https://git.kernel.org/stable/c/c4327229948879814229b46aa26a750718888503

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