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Message-ID: <2025091145-CVE-2025-39759-fa5f@gregkh> Date: Thu, 11 Sep 2025 18:52:59 +0200 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-cve-announce@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...nel.org> Subject: CVE-2025-39759: btrfs: qgroup: fix race between quota disable and quota rescan ioctl From: Greg Kroah-Hartman <gregkh@...nel.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. The Linux kernel CVE team has assigned CVE-2025-39759 to this issue. Affected and fixed versions =========================== Fixed in 6.1.149 with commit 7cda0fdde5d9890976861421d207870500f9aace Fixed in 6.6.103 with commit b172535ccba12f0cf7d23b3b840989de47fc104d Fixed in 6.12.44 with commit dd0b28d877b293b1d7f8727a7de08ae36b6b9ef0 Fixed in 6.15.11 with commit c38028ce0d0045ca600b6a8345a0ff92bfb47b66 Fixed in 6.16.2 with commit 2fd0f5ceb997f90f4332ccbab6c7e907e6b2d0eb Fixed in 6.17-rc1 with commit e1249667750399a48cafcf5945761d39fa584edf Please see https://www.kernel.org for a full list of currently supported kernel versions by the kernel community. Unaffected versions might change over time as fixes are backported to older supported kernel versions. The official CVE entry at https://cve.org/CVERecord/?id=CVE-2025-39759 will be updated if fixes are backported, please check that for the most up to date information about this issue. Affected files ============== The file(s) affected by this issue are: fs/btrfs/qgroup.c Mitigation ========== The Linux kernel CVE team recommends that you update to the latest stable kernel version for this, and many other bugfixes. Individual changes are never tested alone, but rather are part of a larger kernel release. Cherry-picking individual commits is not recommended or supported by the Linux kernel community at all. If however, updating to the latest release is impossible, the individual changes to resolve this issue can be found at these commits: https://git.kernel.org/stable/c/7cda0fdde5d9890976861421d207870500f9aace https://git.kernel.org/stable/c/b172535ccba12f0cf7d23b3b840989de47fc104d https://git.kernel.org/stable/c/dd0b28d877b293b1d7f8727a7de08ae36b6b9ef0 https://git.kernel.org/stable/c/c38028ce0d0045ca600b6a8345a0ff92bfb47b66 https://git.kernel.org/stable/c/2fd0f5ceb997f90f4332ccbab6c7e907e6b2d0eb https://git.kernel.org/stable/c/e1249667750399a48cafcf5945761d39fa584edf
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