Subject: CVE-2024-40957: seg6: fix parameter passing when calling NF_HOOK() in End.DX4 and End.DX6 behaviors

From: Greg Kroah-Hartman <[email-masked]>

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

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

seg6: fix parameter passing when calling NF_HOOK() in End.DX4 and End.DX6 behaviors

input_action_end_dx4() and input_action_end_dx6() are called NF_HOOK() for
PREROUTING hook, in PREROUTING hook, we should passing a valid indev,
and a NULL outdev to NF_HOOK(), otherwise may trigger a NULL pointer
dereference, as below:

    [74830.647293] BUG: kernel NULL pointer dereference, address: 0000000000000090
    [74830.655633] #PF: supervisor read access in kernel mode
    [74830.657888] #PF: error_code(0x0000) - not-present page
    [74830.659500] PGD 0 P4D 0
    [74830.660450] Oops: 0000 [#1] PREEMPT SMP PTI
    ...
    [74830.664953] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
    [74830.666569] RIP: 0010:rpfilter_mt+0x44/0x15e [ipt_rpfilter]
    ...
    [74830.689725] Call Trace:
    [74830.690402]  <IRQ>
    [74830.690953]  ? show_trace_log_lvl+0x1c4/0x2df
    [74830.692020]  ? show_trace_log_lvl+0x1c4/0x2df
    [74830.693095]  ? ipt_do_table+0x286/0x710 [ip_tables]
    [74830.694275]  ? __die_body.cold+0x8/0xd
    [74830.695205]  ? page_fault_oops+0xac/0x140
    [74830.696244]  ? exc_page_fault+0x62/0x150
    [74830.697225]  ? asm_exc_page_fault+0x22/0x30
    [74830.698344]  ? rpfilter_mt+0x44/0x15e [ipt_rpfilter]
    [74830.699540]  ipt_do_table+0x286/0x710 [ip_tables]
    [74830.700758]  ? ip6_route_input+0x19d/0x240
    [74830.701752]  nf_hook_slow+0x3f/0xb0
    [74830.702678]  input_action_end_dx4+0x19b/0x1e0
    [74830.703735]  ? input_action_end_t+0xe0/0xe0
    [74830.704734]  seg6_local_input_core+0x2d/0x60
    [74830.705782]  lwtunnel_input+0x5b/0xb0
    [74830.706690]  __netif_receive_skb_one_core+0x63/0xa0
    [74830.707825]  process_backlog+0x99/0x140
    [74830.709538]  __napi_poll+0x2c/0x160
    [74830.710673]  net_rx_action+0x296/0x350
    [74830.711860]  __do_softirq+0xcb/0x2ac
    [74830.713049]  do_softirq+0x63/0x90

input_action_end_dx4() passing a NULL indev to NF_HOOK(), and finally
trigger a NULL dereference in rpfilter_mt()->rpfilter_is_loopback():

    static bool
    rpfilter_is_loopback(const struct sk_buff *skb,
          	       const struct net_device *in)
    {
            // in is NULL
            return skb->pkt_type == PACKET_LOOPBACK ||
          	 in->flags & IFF_LOOPBACK;
    }

The Linux kernel CVE team has assigned CVE-2024-40957 to this issue.

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

	Issue introduced in 5.15 with commit 7a3f5b0de364 and fixed in 5.15.162 with commit af90e3d73dc4
	Issue introduced in 5.15 with commit 7a3f5b0de364 and fixed in 6.1.96 with commit ec4d970b597e
	Issue introduced in 5.15 with commit 7a3f5b0de364 and fixed in 6.6.36 with commit d62df86c1720
	Issue introduced in 5.15 with commit 7a3f5b0de364 and fixed in 6.9.7 with commit 561475d53aa7
	Issue introduced in 5.15 with commit 7a3f5b0de364 and fixed in 6.10 with commit 9a3bc8d16e0a

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-2024-40957
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/ipv6/seg6_local.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/af90e3d73dc45778767b2fb6e7edd57ebe34380d
	https://git.kernel.org/stable/c/ec4d970b597ee5e17b0d8d73b7875197ce9a04d4
	https://git.kernel.org/stable/c/d62df86c172033679d744f07d89e93e367dd11f6
	https://git.kernel.org/stable/c/561475d53aa7e4511ee7cdba8728ded81cf1db1c
	https://git.kernel.org/stable/c/9a3bc8d16e0aacd65c31aaf23a2bced3288a7779