CVE-2026-45895

/// Technical description

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

quota: fix livelock between quotactl and freeze_super

When a filesystem is frozen, quotactl_block() enters a retry loop

waiting for the filesystem to thaw. It acquires s_umount, checks the

freeze state, drops s_umount and uses sb_start_write() - sb_end_write()

pair to wait for the unfreeze.

However, this retry loop can trigger a livelock issue, specifically on

kernels with preemption disabled.

The mechanism is as follows:

1. freeze_super() sets SB_FREEZE_WRITE and calls sb_wait_write().

2. sb_wait_write() calls percpu_down_write(), which initiates

synchronize_rcu().

3. Simultaneously, quotactl_block() spins in its retry loop, immediately

executing the sb_start_write() - sb_end_write() pair.

4. Because the kernel is non-preemptible and the loop contains no

scheduling points, quotactl_block() never yields the CPU. This

prevents that CPU from reaching an RCU quiescent state.

5. synchronize_rcu() in the fre

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References