CVE-2025-68178
NoneCVSS
—
EPSS
0.2%
Published
Dec 16, 2025
CISA due date
—
Cloudanix analysis
A locking mistake in the Linux kernel can make the system freeze when disk settings and removal operations happen at the same time.
- Exploitation
- Local Privilege
- Attacker needs
- Low Privilege
- Complexity
- Moderate
- Impact
- Denial Of Service
- Component
- OS kernel
- Class
- Race Condition
- Remediation
- Upgrade
- Effort
- Medium
- Patch risk
- Low
What it actually does
Possible deadlock from circular lock dependency between queue usage counter (held during blkg_conf_prep via blk_queue_enter), rq_qos_mutex, and sysfs_lock during concurrent cgroup policy configuration and queue unregistration or disk deletion.
Why it matters to the business
Local operations involving block device cgroup limits or disk hot-removal can trigger system hangs, requiring reboots and interrupting storage-dependent workloads; low exploitability reduces immediate risk but affects kernel stability in environments managing many containers or virtual disks.
How an attack unfolds
An attacker with local access writes to a cgroup blkio file (tg_set_limit) while a concurrent operation removes a disk (del_gendisk), acquiring locks in an order that violates the expected freeze-before-mutex sequence and deadlocks the system.
How to fix it
Upgrade the Linux kernel to a version containing commit e1729523759cda2c0afb76b1c88e0d2f2ef5b7cb; for affected container images such as http-echo on Chainguard or Wolfi, update to version 1.0.0-r12 or later that incorporates the fix.
How to confirm the fix worked
Verify the running kernel includes commit e1729523759cda2c0afb76b1c88e0d2f2ef5b7cb via git log or package version; confirm absence of the lockdep warning on concurrent cgroup writes and disk removal; test policy configuration under load.
Typical attack path
- Obtain local unprivileged or container access
- Write to blkio cgroup controller files to set I/O limits
- Trigger or race with block device removal or queue unregistration
- Cause lock acquisition order violation leading to deadlock
How to detect it
Review kernel logs for lockdep circular locking warnings involving q->sysfs_lock, rq_qos_mutex, and q_usage_counter; inspect dmesg or journalctl for traces showing blkg_conf_prep, del_gendisk, and tg_set_limit during the same timeframe.
What your security team should do
- Prioritize kernel updates on systems exposing block devices to untrusted containers or users
- Monitor for kernel lockdep warnings related to blk-cgroup and sysfs_lock
- Apply fixed package versions (1.0.0-r12 for http-echo images) in container builds
- Review cgroup blkio usage and limit concurrent policy changes with device hotplug operations
The record
In the Linux kernel, the following vulnerability has been resolved: blk-cgroup: fix possible deadlock while configuring policy Following deadlock can be triggered easily by lockdep: WARNING: possible circular locking dependency detected 6.17.0-rc3-00124-ga12c2658ced0 #1665 Not tainted ------------------------------------------------------ check/1334 is trying to acquire lock: ff1100011d9d0678 (&q->sysfs_lock){+.+.}-{4:4}, at: blk_unregister_queue+0x53/0x180 but task is already holding lock: ff1100011d9d00e0 (&q->q_usage_counter(queue)#3){++++}-{0:0}, at: del_gendisk+0xba/0x110 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&q->q_usage_counter(queue)#3){++++}-{0:0}: blk_queue_enter+0x40b/0x470 blkg_conf_prep+0x7b/0x3c0 tg_set_limit+0x10a/0x3e0 cgroup_file_write+0xc6/0x420 kernfs_fop_write_iter+0x189/0x280 vfs_write+0x256/0x490 ksys_write+0x83/0x190 __x64_sys_write+0x21/0x30 x64_sys_call+0x4608/0x4630 do_syscall_64+0xdb/0x6b0 entry_SYSCALL_64_after_hwframe+0x76/0x7e -> #1 (&q->rq_qos_mutex){+.+.}-{4:4}: __mutex_lock+0xd8/0xf50 mutex_lock_nested+0x2b/0x40 wbt_init+0x17e/0x280 wbt_enable_default+0xe9/0x140 blk_register_queue+0x1da/0x2e0 __add_disk+0x38c/0x5d0 add_disk_fwnode+0x89/0x250 device_add_disk+0x18/0x30 virtblk_probe+0x13a3/0x1800 virtio_dev_probe+0x389/0x610 really_probe+0x136/0x620 __driver_probe_device+0xb3/0x230 driver_probe_device+0x2f/0xe0 __driver_attach+0x158/0x250 bus_for_each_dev+0xa9/0x130 driver_attach+0x26/0x40 bus_add_driver+0x178/0x3d0 driver_register+0x7d/0x1c0 __register_virtio_driver+0x2c/0x60 virtio_blk_init+0x6f/0xe0 do_one_initcall+0x94/0x540 kernel_init_freeable+0x56a/0x7b0 kernel_init+0x2b/0x270 ret_from_fork+0x268/0x4c0 ret_from_fork_asm+0x1a/0x30 -> #0 (&q->sysfs_lock){+.+.}-{4:4}: __lock_acquire+0x1835/0x2940 lock_acquire+0xf9/0x450 __mutex_lock+0xd8/0xf50 mutex_lock_nested+0x2b/0x40 blk_unregister_queue+0x53/0x180 __del_gendisk+0x226/0x690 del_gendisk+0xba/0x110 sd_remove+0x49/0xb0 [sd_mod] device_remove+0x87/0xb0 device_release_driver_internal+0x11e/0x230 device_release_driver+0x1a/0x30 bus_remove_device+0x14d/0x220 device_del+0x1e1/0x5a0 __scsi_remove_device+0x1ff/0x2f0 scsi_remove_device+0x37/0x60 sdev_store_delete+0x77/0x100 dev_attr_store+0x1f/0x40 sysfs_kf_write+0x65/0x90 kernfs_fop_write_iter+0x189/0x280 vfs_write+0x256/0x490 ksys_write+0x83/0x190 __x64_sys_write+0x21/0x30 x64_sys_call+0x4608/0x4630 do_syscall_64+0xdb/0x6b0 entry_SYSCALL_64_after_hwframe+0x76/0x7e other info that might help us debug this: Chain exists of: &q->sysfs_lock --> &q->rq_qos_mutex --> &q->q_usage_counter(queue)#3 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&q->q_usage_counter(queue)#3); lock(&q->rq_qos_mutex); lock(&q->q_usage_counter(queue)#3); lock(&q->sysfs_lock); Root cause is that queue_usage_counter is grabbed with rq_qos_mutex held in blkg_conf_prep(), while queue should be freezed before rq_qos_mutex from other context. The blk_queue_enter() from blkg_conf_prep() is used to protect against policy deactivation, which is already protected with blkcg_mutex, hence convert blk_queue_enter() to blkcg_mutex to fix this problem. Meanwhile, consider that blkcg_mutex is held after queue is freezed from policy deactivation, also convert blkg_alloc() to use GFP_NOIO.
Affected packages
| Ecosystem | Package | Introduced | Fixed |
|---|---|---|---|
| Linux | Kernel | 0 | 6.6.117 |
| Linux | Kernel | 6.5.0 | 6.6.117 |
| Mageia:9 | kernel | 0 | 6.6.120-1.mga9 |
| Mageia:9 | kernel-linus | 0 | 6.6.120-1.mga9 |
| Mageia:9 | kmod-virtualbox | 0 | 7.1.14-14.mga9 |
| Mageia:9 | kmod-xtables-addons | 0 | 3.24-88.mga9 |
| openSUSE:Leap 16.0 | dtb-aarch64 | 0 | 6.12.0-160000.26.1 |
| openSUSE:Leap 16.0 | kernel-64kb | 0 | 6.12.0-160000.26.1 |
| openSUSE:Leap 16.0 | kernel-azure | 0 | 6.12.0-160000.26.1 |
| openSUSE:Leap 16.0 | kernel-default | 0 | 6.12.0-160000.26.1 |
| openSUSE:Leap 16.0 | kernel-default-base | 0 | 6.12.0-160000.26.1.160000.2.7 |
| openSUSE:Leap 16.0 | kernel-docs | 0 | 6.12.0-160000.26.1 |
| openSUSE:Leap 16.0 | kernel-kvmsmall | 0 | 6.12.0-160000.26.1 |
| openSUSE:Leap 16.0 | kernel-obs-build | 0 | 6.12.0-160000.26.1 |
| openSUSE:Leap 16.0 | kernel-obs-qa | 0 | 6.12.0-160000.26.1 |
| openSUSE:Leap 16.0 | kernel-rt | 0 | 6.12.0-160000.26.1 |
| openSUSE:Leap 16.0 | kernel-source | 0 | 6.12.0-160000.26.1 |
| openSUSE:Leap 16.0 | kernel-syms | 0 | 6.12.0-160000.26.1 |
| openSUSE:Leap 16.0 | kernel-zfcpdump | 0 | 6.12.0-160000.26.1 |
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