CVE-2026-45895 (GCVE-0-2026-45895)

Vulnerability from cvelistv5 – Published: 2026-05-27 12:17 – Updated: 2026-05-27 12:17
VLAI
Title
quota: fix livelock between quotactl and freeze_super
Summary
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 freezer thread waits indefinitely for the quotactl_block() CPU to report a quiescent state. 6. quotactl_block() spins indefinitely waiting for the freezer to advance, which it cannot do as it is blocked on the RCU sync. This results in a hang of the freezer process and 100% CPU usage by the quota process. While this can occur intermittently on multi-core systems, it is reliably reproducing on a node with the following script, running both the freezer and the quota toggle on the same CPU: # mkfs.ext4 -O quota /dev/sda 2g && mkdir a_mount # mount /dev/sda -o quota,usrquota,grpquota a_mount # taskset -c 3 bash -c "while true; do xfs_freeze -f a_mount; \ xfs_freeze -u a_mount; done" & # taskset -c 3 bash -c "while true; do quotaon a_mount; \ quotaoff a_mount; done" & Adding cond_resched() to the retry loop fixes the issue. It acts as an RCU quiescent state, allowing synchronize_rcu() in percpu_down_write() to complete.
Severity
5.5 (Medium)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6971 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 576215cffdefc1f0ceebffd87abb390926e6b037 , < 37ccd48cf35f3c8b9f2ea961a7b486b91eb71a82 (git)
Affected: 576215cffdefc1f0ceebffd87abb390926e6b037 , < 414259caf81a397563fc9baca9c0ef856c4a97cf (git)
Affected: 576215cffdefc1f0ceebffd87abb390926e6b037 , < 02bb1500f1479750e6557c8044f6a2d7e9d30c12 (git)
Affected: 576215cffdefc1f0ceebffd87abb390926e6b037 , < 53b2314b26b6640a3657cc924de63a1a8f26ac4d (git)
Affected: 576215cffdefc1f0ceebffd87abb390926e6b037 , < 77449e453dfc006ad738dec55374c4cbc056fd39 (git)
guessed Create a notification for this product.
Linux Linux Affected: 6.5
Unaffected: 0 , < 6.5 (semver)
Unaffected: 6.6.128 , ≤ 6.6.* (semver)
Unaffected: 6.12.75 , ≤ 6.12.* (semver)
Unaffected: 6.18.14 , ≤ 6.18.* (semver)
Unaffected: 6.19.4 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
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Show details on NVD website
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      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-45895",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/2026/cve-2026-45895.json",
      "version": "10"
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}



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How durations are calculated

Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.

Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.

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