Subject: CVE-2024-26834: netfilter: nft_flow_offload: release dst in case direct xmit path is used

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

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

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

netfilter: nft_flow_offload: release dst in case direct xmit path is used

Direct xmit does not use it since it calls dev_queue_xmit() to send
packets, hence it calls dst_release().

kmemleak reports:

unreferenced object 0xffff88814f440900 (size 184):
  comm "softirq", pid 0, jiffies 4294951896
  hex dump (first 32 bytes):
    00 60 5b 04 81 88 ff ff 00 e6 e8 82 ff ff ff ff  .`[.............
    21 0b 50 82 ff ff ff ff 00 00 00 00 00 00 00 00  !.P.............
  backtrace (crc cb2bf5d6):
    [<000000003ee17107>] kmem_cache_alloc+0x286/0x340
    [<0000000021a5de2c>] dst_alloc+0x43/0xb0
    [<00000000f0671159>] rt_dst_alloc+0x2e/0x190
    [<00000000fe5092c9>] __mkroute_output+0x244/0x980
    [<000000005fb96fb0>] ip_route_output_flow+0xc0/0x160
    [<0000000045367433>] nf_ip_route+0xf/0x30
    [<0000000085da1d8e>] nf_route+0x2d/0x60
    [<00000000d1ecd1cb>] nft_flow_route+0x171/0x6a0 [nft_flow_offload]
    [<00000000d9b2fb60>] nft_flow_offload_eval+0x4e8/0x700 [nft_flow_offload]
    [<000000009f447dbb>] expr_call_ops_eval+0x53/0x330 [nf_tables]
    [<00000000072e1be6>] nft_do_chain+0x17c/0x840 [nf_tables]
    [<00000000d0551029>] nft_do_chain_inet+0xa1/0x210 [nf_tables]
    [<0000000097c9d5c6>] nf_hook_slow+0x5b/0x160
    [<0000000005eccab1>] ip_forward+0x8b6/0x9b0
    [<00000000553a269b>] ip_rcv+0x221/0x230
    [<00000000412872e5>] __netif_receive_skb_one_core+0xfe/0x110

The Linux kernel CVE team has assigned CVE-2024-26834 to this issue.

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

	Issue introduced in 6.5 with commit fa502c865666 and fixed in 6.6.19 with commit 9256ab9232e3
	Issue introduced in 6.5 with commit fa502c865666 and fixed in 6.7.7 with commit 2d17cf10179a
	Issue introduced in 6.5 with commit fa502c865666 and fixed in 6.8 with commit 8762785f459b

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-2024-26834
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/netfilter/nf_flow_table_core.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/13b57b5cd591d5b22f9bbf047b2922967de411f3
	https://git.kernel.org/stable/c/a6cafdb49a7bbf4a88367db209703eee6941e023
	https://git.kernel.org/stable/c/9256ab9232e35a16af9c30fa4e522e6d1bd3605a
	https://git.kernel.org/stable/c/2d17cf10179a7de6d8f0128168b84ad0b4a1863f
	https://git.kernel.org/stable/c/8762785f459be1cfe6fcf7285c123aad6a3703f0