linux-cve-announce - CVE-2025-38165: bpf, sockmap: Fix panic when calling skb

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Message-ID: <2025070341-CVE-2025-38165-0d70@gregkh>
Date: Thu,  3 Jul 2025 10:36:21 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-38165: bpf, sockmap: Fix panic when calling skb_linearize

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

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

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

bpf, sockmap: Fix panic when calling skb_linearize

The panic can be reproduced by executing the command:
./bench sockmap -c 2 -p 1 -a --rx-verdict-ingress --rx-strp 100000

Then a kernel panic was captured:
'''
[  657.460555] kernel BUG at net/core/skbuff.c:2178!
[  657.462680] Tainted: [W]=WARN
[  657.463287] Workqueue: events sk_psock_backlog
...
[  657.469610]  <TASK>
[  657.469738]  ? die+0x36/0x90
[  657.469916]  ? do_trap+0x1d0/0x270
[  657.470118]  ? pskb_expand_head+0x612/0xf40
[  657.470376]  ? pskb_expand_head+0x612/0xf40
[  657.470620]  ? do_error_trap+0xa3/0x170
[  657.470846]  ? pskb_expand_head+0x612/0xf40
[  657.471092]  ? handle_invalid_op+0x2c/0x40
[  657.471335]  ? pskb_expand_head+0x612/0xf40
[  657.471579]  ? exc_invalid_op+0x2d/0x40
[  657.471805]  ? asm_exc_invalid_op+0x1a/0x20
[  657.472052]  ? pskb_expand_head+0xd1/0xf40
[  657.472292]  ? pskb_expand_head+0x612/0xf40
[  657.472540]  ? lock_acquire+0x18f/0x4e0
[  657.472766]  ? find_held_lock+0x2d/0x110
[  657.472999]  ? __pfx_pskb_expand_head+0x10/0x10
[  657.473263]  ? __kmalloc_cache_noprof+0x5b/0x470
[  657.473537]  ? __pfx___lock_release.isra.0+0x10/0x10
[  657.473826]  __pskb_pull_tail+0xfd/0x1d20
[  657.474062]  ? __kasan_slab_alloc+0x4e/0x90
[  657.474707]  sk_psock_skb_ingress_enqueue+0x3bf/0x510
[  657.475392]  ? __kasan_kmalloc+0xaa/0xb0
[  657.476010]  sk_psock_backlog+0x5cf/0xd70
[  657.476637]  process_one_work+0x858/0x1a20
'''

The panic originates from the assertion BUG_ON(skb_shared(skb)) in
skb_linearize(). A previous commit(see Fixes tag) introduced skb_get()
to avoid race conditions between skb operations in the backlog and skb
release in the recvmsg path. However, this caused the panic to always
occur when skb_linearize is executed.

The "--rx-strp 100000" parameter forces the RX path to use the strparser
module which aggregates data until it reaches 100KB before calling sockmap
logic. The 100KB payload exceeds MAX_MSG_FRAGS, triggering skb_linearize.

To fix this issue, just move skb_get into sk_psock_skb_ingress_enqueue.

'''
sk_psock_backlog:
    sk_psock_handle_skb
       skb_get(skb) <== we move it into 'sk_psock_skb_ingress_enqueue'
       sk_psock_skb_ingress____________
                                       ↓
                                       |
                                       | → sk_psock_skb_ingress_self
                                       |      sk_psock_skb_ingress_enqueue
sk_psock_verdict_apply_________________↑          skb_linearize
'''

Note that for verdict_apply path, the skb_get operation is unnecessary so
we add 'take_ref' param to control it's behavior.

The Linux kernel CVE team has assigned CVE-2025-38165 to this issue.


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

	Issue introduced in 6.1.54 with commit 923877254f002ae87d441382bb1096d9e773d56d and fixed in 6.1.142 with commit 9718ba6490732dbe70190d42c21deb1440834402
	Issue introduced in 6.6 with commit a454d84ee20baf7bd7be90721b9821f73c7d23d9 and fixed in 6.6.94 with commit db1d15a26f21f97459508c42ae87cabe8d3afc3b
	Issue introduced in 6.6 with commit a454d84ee20baf7bd7be90721b9821f73c7d23d9 and fixed in 6.12.34 with commit 3d25fa2d7f127348c818e1dab9e58534f7ac56cc
	Issue introduced in 6.6 with commit a454d84ee20baf7bd7be90721b9821f73c7d23d9 and fixed in 6.15.3 with commit e9c1299d813fc04668042690f2c3cc76d013959a
	Issue introduced in 6.6 with commit a454d84ee20baf7bd7be90721b9821f73c7d23d9 and fixed in 6.16-rc1 with commit 5ca2e29f6834c64c0e5a9ccf1278c21fb49b827e
	Issue introduced in 6.5.4 with commit e6b5e47adb9166e732cdf7e6e034946e3f89f36d

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-2025-38165
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/skmsg.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/9718ba6490732dbe70190d42c21deb1440834402
	https://git.kernel.org/stable/c/db1d15a26f21f97459508c42ae87cabe8d3afc3b
	https://git.kernel.org/stable/c/3d25fa2d7f127348c818e1dab9e58534f7ac56cc
	https://git.kernel.org/stable/c/e9c1299d813fc04668042690f2c3cc76d013959a
	https://git.kernel.org/stable/c/5ca2e29f6834c64c0e5a9ccf1278c21fb49b827e