CVE-2025-39759
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2025-09-11

Last updated on: 2025-11-03

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: btrfs: qgroup: fix race between quota disable and quota rescan ioctl There's a race between a task disabling quotas and another running the rescan ioctl that can result in a use-after-free of qgroup records from the fs_info->qgroup_tree rbtree. This happens as follows: 1) Task A enters btrfs_ioctl_quota_rescan() -> btrfs_qgroup_rescan(); 2) Task B enters btrfs_quota_disable() and calls btrfs_qgroup_wait_for_completion(), which does nothing because at that point fs_info->qgroup_rescan_running is false (it wasn't set yet by task A); 3) Task B calls btrfs_free_qgroup_config() which starts freeing qgroups from fs_info->qgroup_tree without taking the lock fs_info->qgroup_lock; 4) Task A enters qgroup_rescan_zero_tracking() which starts iterating the fs_info->qgroup_tree tree while holding fs_info->qgroup_lock, but task B is freeing qgroup records from that tree without holding the lock, resulting in a use-after-free. Fix this by taking fs_info->qgroup_lock at btrfs_free_qgroup_config(). Also at btrfs_qgroup_rescan() don't start the rescan worker if quotas were already disabled.
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Meta Information
Published
2025-09-11
Last Modified
2025-11-03
Generated
2026-05-07
AI Q&A
2025-09-11
EPSS Evaluated
2026-05-05
NVD
CVE-2025-39759
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel 6.1.153
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-UNKNOWN
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AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability is a race condition in the Linux kernel's btrfs filesystem quota management. It occurs when one task disables quotas while another task is running a quota rescan ioctl. Due to improper locking, this can lead to a use-after-free situation where quota group records are freed while still being accessed, potentially causing system instability or crashes. The issue arises because one task frees quota group data without holding the necessary lock, while another task simultaneously iterates over that data holding the lock.


How can this vulnerability impact me? :

This vulnerability can lead to use-after-free conditions in the kernel, which may cause system crashes, data corruption, or potential escalation of privileges if exploited. It affects the stability and reliability of systems using the btrfs filesystem with quota management enabled, potentially impacting system availability and data integrity.


What immediate steps should I take to mitigate this vulnerability?

To mitigate this vulnerability, update the Linux kernel to a version where the race condition between quota disable and quota rescan ioctl in btrfs has been fixed. The fix involves proper locking in btrfs_free_qgroup_config() and preventing the rescan worker from starting if quotas are disabled. Until the update is applied, avoid running quota disable and quota rescan ioctl operations concurrently on btrfs filesystems.


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