CVE-2023-54177: 
Linux Kernel vulnerability analysis and mitigation

CVE-2023-54177 is a Linux kernel vulnerability in the quota subsystem, specifically a race condition that triggers a kernel warning in dqgrab() during concurrent filesystem reconfiguration operations. It affects the Linux kernel and was publicly disclosed on December 30, 2025, when it was assigned a CVE and published to NVD. The vulnerability has a CVSS v3.1 base score of 5.5 (Medium), with a local attack vector requiring low privileges (Red Hat Bugzilla, Red Hat CVE).

The root cause is a race condition (CWE-362) in the Linux kernel's disk quota subsystem (fs/quota/). The issue arises when three concurrent processes interact: one suspends quota via dquot_suspend, a second resumes quota via dquot_resume (calling dquot_load_quota_sb → add_dquot_ref), and a third opens a file with O_RDWR, triggering dquot_initialize → dqget, which increments dquot->dq_count without the DQ_ACTIVE_B flag being set. When dquot_disable subsequently calls invalidate_dquots and finds a non-zero dq_count, it calls dqgrab(), which asserts DQ_ACTIVE_B is set via WARN_ON_ONCE, triggering the kernel warning. The fix replaces the dqgrab() call in invalidate_dquots() with a direct atomic_inc(&dquot->dq_count) to avoid the incorrect assertion (Red Hat Bugzilla).

Successful triggering of this vulnerability results in a kernel WARN_ON_ONCE warning, which can cause availability impact on affected Linux systems — particularly those using disk quotas with ext4 or similar filesystems. The warning is triggered in dquot_disable+0x13b7/0x18c0 and may lead to system instability or denial of service under specific concurrent workload conditions. There is no confidentiality or integrity impact; the vulnerability is limited to availability (CVSS availability impact: High) (Red Hat CVE).

The fix is available in the upstream Linux kernel via patches committed to the stable kernel tree (commits 3f378783c47b, 6f4e543d277a, 579d814de87c, 965bad2bf1af). Users should update to a patched kernel version that includes the quota fix for dqgrab(). Red Hat has tracked this issue in Bugzilla (Bug 2426252) with severity rated as low; users of Red Hat Enterprise Linux should monitor for updated kernel packages. As a workaround, disabling disk quotas on affected filesystems would prevent the race condition from being triggered (Red Hat Bugzilla).