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Message-ID: <2026011313-CVE-2025-68815-2112@gregkh>
Date: Tue, 13 Jan 2026 16:29:41 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-68815: net/sched: ets: Remove drr class from the active list if it changes to strict
From: Greg Kroah-Hartman <gregkh@...nel.org>
Description
===========
In the Linux kernel, the following vulnerability has been resolved:
net/sched: ets: Remove drr class from the active list if it changes to strict
Whenever a user issues an ets qdisc change command, transforming a
drr class into a strict one, the ets code isn't checking whether that
class was in the active list and removing it. This means that, if a
user changes a strict class (which was in the active list) back to a drr
one, that class will be added twice to the active list [1].
Doing so with the following commands:
tc qdisc add dev lo root handle 1: ets bands 2 strict 1
tc qdisc add dev lo parent 1:2 handle 20: \
tbf rate 8bit burst 100b latency 1s
tc filter add dev lo parent 1: basic classid 1:2
ping -c1 -W0.01 -s 56 127.0.0.1
tc qdisc change dev lo root handle 1: ets bands 2 strict 2
tc qdisc change dev lo root handle 1: ets bands 2 strict 1
ping -c1 -W0.01 -s 56 127.0.0.1
Will trigger the following splat with list debug turned on:
[ 59.279014][ T365] ------------[ cut here ]------------
[ 59.279452][ T365] list_add double add: new=ffff88801d60e350, prev=ffff88801d60e350, next=ffff88801d60e2c0.
[ 59.280153][ T365] WARNING: CPU: 3 PID: 365 at lib/list_debug.c:35 __list_add_valid_or_report+0x17f/0x220
[ 59.280860][ T365] Modules linked in:
[ 59.281165][ T365] CPU: 3 UID: 0 PID: 365 Comm: tc Not tainted 6.18.0-rc7-00105-g7e9f13163c13-dirty #239 PREEMPT(voluntary)
[ 59.281977][ T365] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[ 59.282391][ T365] RIP: 0010:__list_add_valid_or_report+0x17f/0x220
[ 59.282842][ T365] Code: 89 c6 e8 d4 b7 0d ff 90 0f 0b 90 90 31 c0 e9 31 ff ff ff 90 48 c7 c7 e0 a0 22 9f 48 89 f2 48 89 c1 4c 89 c6 e8 b2 b7 0d ff 90 <0f> 0b 90 90 31 c0 e9 0f ff ff ff 48 89 f7 48 89 44 24 10 4c 89 44
...
[ 59.288812][ T365] Call Trace:
[ 59.289056][ T365] <TASK>
[ 59.289224][ T365] ? srso_alias_return_thunk+0x5/0xfbef5
[ 59.289546][ T365] ets_qdisc_change+0xd2b/0x1e80
[ 59.289891][ T365] ? __lock_acquire+0x7e7/0x1be0
[ 59.290223][ T365] ? __pfx_ets_qdisc_change+0x10/0x10
[ 59.290546][ T365] ? srso_alias_return_thunk+0x5/0xfbef5
[ 59.290898][ T365] ? __mutex_trylock_common+0xda/0x240
[ 59.291228][ T365] ? __pfx___mutex_trylock_common+0x10/0x10
[ 59.291655][ T365] ? srso_alias_return_thunk+0x5/0xfbef5
[ 59.291993][ T365] ? srso_alias_return_thunk+0x5/0xfbef5
[ 59.292313][ T365] ? trace_contention_end+0xc8/0x110
[ 59.292656][ T365] ? srso_alias_return_thunk+0x5/0xfbef5
[ 59.293022][ T365] ? srso_alias_return_thunk+0x5/0xfbef5
[ 59.293351][ T365] tc_modify_qdisc+0x63a/0x1cf0
Fix this by always checking and removing an ets class from the active list
when changing it to strict.
[1] https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git/tree/net/sched/sch_ets.c?id=ce052b9402e461a9aded599f5b47e76bc727f7de#n663
The Linux kernel CVE team has assigned CVE-2025-68815 to this issue.
Affected and fixed versions
===========================
Issue introduced in 5.14 with commit cd9b50adc6bb9ad3f7d244590a389522215865c4 and fixed in 6.1.160 with commit 8067db5c95aab9461d23117679338cd8869831fa
Issue introduced in 5.14 with commit cd9b50adc6bb9ad3f7d244590a389522215865c4 and fixed in 6.6.120 with commit 2f125ebe47d6369e562f3cbd9b6227cff51eaf34
Issue introduced in 5.14 with commit cd9b50adc6bb9ad3f7d244590a389522215865c4 and fixed in 6.12.64 with commit cca2ed931b734fe48139bc6f020e47367346630f
Issue introduced in 5.14 with commit cd9b50adc6bb9ad3f7d244590a389522215865c4 and fixed in 6.18.3 with commit 43d9a530c8c094d137159784e7c951c65f11ec6c
Issue introduced in 5.14 with commit cd9b50adc6bb9ad3f7d244590a389522215865c4 and fixed in 6.19-rc2 with commit b1e125ae425aba9b45252e933ca8df52a843ec70
Issue introduced in 5.10.62 with commit f517335a61ff8037b18ba1b0a002c1f82926a934
Issue introduced in 5.13.14 with commit d05330672afe2e142ba97e63bd7c1faef76781bb
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-2025-68815
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/sched/sch_ets.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/8067db5c95aab9461d23117679338cd8869831fa
https://git.kernel.org/stable/c/2f125ebe47d6369e562f3cbd9b6227cff51eaf34
https://git.kernel.org/stable/c/cca2ed931b734fe48139bc6f020e47367346630f
https://git.kernel.org/stable/c/43d9a530c8c094d137159784e7c951c65f11ec6c
https://git.kernel.org/stable/c/b1e125ae425aba9b45252e933ca8df52a843ec70
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