# CVE-2023-52897: linux: In the Linux kernel, the following vulnerability has been resolved:  btrfs: qgroup: do not warn on record without old...

CVE-2023-52897 is fixed in linux on 1 platform, first by DEBIAN-CVE-2023-52897, released August 21, 2024. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2023-52897
- Priority: Routine
- CVSS: 4.7 (medium)
- EPSS: 0.0020
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Aug 21, 2024

## Description

In the Linux kernel, the following vulnerability has been resolved:  btrfs: qgroup: do not warn on record without old_roots populated  [BUG] There are some reports from the mailing list that since v6.1 kernel, the WARN_ON() inside btrfs_qgroup_account_extent() gets triggered during rescan:    WARNING: CPU: 3 PID: 6424 at fs/btrfs/qgroup.c:2756 btrfs_qgroup_account_extents+0x1ae/0x260 [btrfs]   CPU: 3 PID: 6424 Comm: snapperd Tainted: P           OE      6.1.2-1-default #1 openSUSE Tumbleweed 05c7a1b1b61d5627475528f71f50444637b5aad7   RIP: 0010:btrfs_qgroup_account_extents+0x1ae/0x260 [btrfs]   Call Trace:    <TASK>   btrfs_commit_transaction+0x30c/0xb40 [btrfs c39c9c546c241c593f03bd6d5f39ea1b676250f6]    ? start_transaction+0xc3/0x5b0 [btrfs c39c9c546c241c593f03bd6d5f39ea1b676250f6]   btrfs_qgroup_rescan+0x42/0xc0 [btrfs c39c9c546c241c593f03bd6d5f39ea1b676250f6]    btrfs_ioctl+0x1ab9/0x25c0 [btrfs c39c9c546c241c593f03bd6d5f39ea1b676250f6]    ? __rseq_handle_notify_resume+0xa9/0x4a0    ? mntput_no_expire+0x4a/0x240    ? __seccomp_filter+0x319/0x4d0    __x64_sys_ioctl+0x90/0xd0    do_syscall_64+0x5b/0x80    ? syscall_exit_to_user_mode+0x17/0x40    ? do_syscall_64+0x67/0x80   entry_SYSCALL_64_after_hwframe+0x63/0xcd   RIP: 0033:0x7fd9b790d9bf    </TASK>  [CAUSE] Since commit e15e9f43c7ca ("btrfs: introduce BTRFS_QGROUP_RUNTIME_FLAG_NO_ACCOUNTING to skip qgroup accounting"), if our qgroup is already in inconsistent state, we will no longer do the time-consuming backref walk.  This can leave some qgroup records without a valid old_roots ulist. Normally this is fine, as btrfs_qgroup_account_extents() would also skip those records if we have NO_ACCOUNTING flag set.  But there is a small window, if we have NO_ACCOUNTING flag set, and inserted some qgroup_record without a old_roots ulist, but then the user triggered a qgroup rescan.  During btrfs_qgroup_rescan(), we firstly clear NO_ACCOUNTING flag, then commit current transaction.  And since we have a qgroup_record with old_roots = NULL, we trigger the WARN_ON() during btrfs_qgroup_account_extents().  [FIX] Unfortunately due to the introduction of NO_ACCOUNTING flag, the assumption that every qgroup_record would have its old_roots populated is no longer correct.  Fix the false alerts and drop the WARN_ON().

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 6.1.8-1 | [DEBIAN-CVE-2023-52897](https://patchblox.com/security/data/fix/linux/debian-cve-2023-52897.md) | Aug 21, 2024 |
| Linux | linux Debian 13.5 (trixie) | 6.1.8-1 | [DEBIAN-CVE-2023-52897](https://patchblox.com/security/data/fix/linux/debian-cve-2023-52897.md) | Aug 21, 2024 |
| Linux | linux Debian 14 | 6.1.8-1 | [DEBIAN-CVE-2023-52897](https://patchblox.com/security/data/fix/linux/debian-cve-2023-52897.md) | Aug 21, 2024 |

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