Google: sys-kernel/csql-kernel-6_6: security update to 19165.0.0

medium Tenable Cloud Security Plugin ID 454909

Description

There are packages installed that are affected by a vulnerability referenced in the following CVE:

- In the Linux kernel, the following vulnerability has been resolved: bpf: Cancel the running bpf_timer
through kworker for PREEMPT_RT During the update procedure, when overwrite element in a pre-allocated
htab, the freeing of old_element is protected by the bucket lock. The reason why the bucket lock is
necessary is that the old_element has already been stashed in htab->extra_elems after alloc_htab_elem()
returns. If freeing the old_element after the bucket lock is unlocked, the stashed element may be reused
by concurrent update procedure and the freeing of old_element will run concurrently with the reuse of the
old_element. However, the invocation of check_and_free_fields() may acquire a spin-lock which violates the
lockdep rule because its caller has already held a raw-spin-lock (bucket lock). The following warning will
be reported when such race happens: BUG: scheduling while atomic: test_progs/676/0x00000003 3 locks held
by test_progs/676: #0: ffffffff864b0240 (rcu_read_lock_trace){....}-{0:0}, at:
bpf_prog_test_run_syscall+0x2c0/0x830 #1: ffff88810e961188 (&htab->lockdep_key){....}-{2:2}, at:
htab_map_update_elem+0x306/0x1500 #2: ffff8881f4eac1b8 (&base->softirq_expiry_lock){....}-{2:2}, at:
hrtimer_cancel_wait_running+0xe9/0x1b0 Modules linked in: bpf_testmod(O) Preemption disabled at:
[<ffffffff817837a3>] htab_map_update_elem+0x293/0x1500 CPU: 0 UID: 0 PID: 676 Comm: test_progs Tainted: G
... 6.12.0+ #11 Tainted: [W]=WARN, [O]=OOT_MODULE Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)...
Call Trace: <TASK> dump_stack_lvl+0x57/0x70 dump_stack+0x10/0x20 __schedule_bug+0x120/0x170
__schedule+0x300c/0x4800 schedule_rtlock+0x37/0x60 rtlock_slowlock_locked+0x6d9/0x54c0
rt_spin_lock+0x168/0x230 hrtimer_cancel_wait_running+0xe9/0x1b0 hrtimer_cancel+0x24/0x30
bpf_timer_delete_work+0x1d/0x40 bpf_timer_cancel_and_free+0x5e/0x80 bpf_obj_free_fields+0x262/0x4a0
check_and_free_fields+0x1d0/0x280 htab_map_update_elem+0x7fc/0x1500
bpf_prog_9f90bc20768e0cb9_overwrite_cb+0x3f/0x43 bpf_prog_ea601c4649694dbd_overwrite_timer+0x5d/0x7e
bpf_prog_test_run_syscall+0x322/0x830 __sys_bpf+0x135d/0x3ca0 __x64_sys_bpf+0x75/0xb0
x64_sys_call+0x1b5/0xa10 do_syscall_64+0x3b/0xc0 entry_SYSCALL_64_after_hwframe+0x4b/0x53 ... </TASK> It
seems feasible to break the reuse and refill of per-cpu extra_elems into two independent parts: reuse the
per-cpu extra_elems with bucket lock being held and refill the old_element as per-cpu extra_elems after
the bucket lock is unlocked. However, it will make the concurrent overwrite procedures on the same CPU
return unexpected -E2BIG error when the map is full. Therefore, the patch fixes the lock problem by
breaking the cancelling of bpf_timer into two steps for PREEMPT_RT: 1) use hrtimer_try_to_cancel() and
check its return value 2) if the timer is running, use hrtimer_cancel() through a kworker to cancel it
again Considering that the current implementation of hrtimer_cancel() will try to acquire a being held
softirq_expiry_lock when the current timer is running, these steps above are reasonable. However, it also
has downside. When the timer is running, the cancelling of the timer is delayed when releasing the last
map uref. The delay is also fixable (e.g., break the cancelling of bpf timer into two parts: one part in
locked scope, another one in unlocked scope), it can be revised later if necessary. It is a bit hard to
decide the right fix tag. One reason is that the problem depends on PREEMPT_RT which is enabled in v6.12.
Considering the softirq_expiry_lock lock exists since v5.4 and bpf_timer is introduced in v5.15, the
bpf_timer commit is used in the fixes tag and an extra depends-on tag is added to state the dependency on
PREEMPT_RT. Depends-on: v6.12+ with PREEMPT_RT enabled (CVE-2025-21825)

Solution

Update the sys-kernel/csql-kernel-6_6 library and its related packages to version 19165.0.0 or later.

Plugin Details

Severity: Medium

ID: 454909

Version: Revision 1.1

Type: Local

Family: Google COS Security Checks

Published: 10/1/2026

Updated: 10/1/2026

Risk Information

VPR

Risk Factor: Low

Score: 3

Percentile: 23.18

Vendor

Vendor Severity: MEDIUM

CVSS v2

Risk Factor: Low

Base Score: 3.8

Temporal Score: 2.8

Vector: CVSS2#AV:L/AC:H/Au:S/C:N/I:N/A:C

CVSS Score Source: CVE-2025-21825

CVSS v3

Risk Factor: Medium

Base Score: 4.7

Temporal Score: 4.1

Vector: CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

Exploit Ease: No known exploits are available

Vulnerability Publication Date: 3/6/2025

Reference Information

CVE: CVE-2025-21825

Detections

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