quota: fix livelock between quotactl and freeze_super
Summary
| CVE | CVE-2026-45895 |
|---|---|
| State | PUBLISHED |
| Assigner | Linux |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-05-27 14:17:03 UTC |
| Updated | 2026-05-27 14:48:31 UTC |
| 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 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. |
Risk And Classification
EPSS: 0.000180000 probability, percentile 0.050770000 (date 2026-06-01)
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Linux | Linux | affected 576215cffdefc1f0ceebffd87abb390926e6b037 37ccd48cf35f3c8b9f2ea961a7b486b91eb71a82 git | Not specified |
| CNA | Linux | Linux | affected 576215cffdefc1f0ceebffd87abb390926e6b037 414259caf81a397563fc9baca9c0ef856c4a97cf git | Not specified |
| CNA | Linux | Linux | affected 576215cffdefc1f0ceebffd87abb390926e6b037 02bb1500f1479750e6557c8044f6a2d7e9d30c12 git | Not specified |
| CNA | Linux | Linux | affected 576215cffdefc1f0ceebffd87abb390926e6b037 53b2314b26b6640a3657cc924de63a1a8f26ac4d git | Not specified |
| CNA | Linux | Linux | affected 576215cffdefc1f0ceebffd87abb390926e6b037 77449e453dfc006ad738dec55374c4cbc056fd39 git | Not specified |
| CNA | Linux | Linux | affected 6.5 | Not specified |
| CNA | Linux | Linux | unaffected 6.5 semver | Not specified |
| CNA | Linux | Linux | unaffected 6.6.128 6.6.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.12.75 6.12.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.18.14 6.18.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.19.4 6.19.* semver | Not specified |
| CNA | Linux | Linux | unaffected 7.0 * original_commit_for_fix | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| git.kernel.org/stable/c/02bb1500f1479750e6557c8044f6a2d7e9d30c12 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/77449e453dfc006ad738dec55374c4cbc056fd39 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/414259caf81a397563fc9baca9c0ef856c4a97cf | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/37ccd48cf35f3c8b9f2ea961a7b486b91eb71a82 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/53b2314b26b6640a3657cc924de63a1a8f26ac4d | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
No vendor comments have been submitted for this CVE.
There are currently no legacy QID mappings associated with this CVE.