CVE-2023-52896

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

btrfs: fix race between quota rescan and disable leading to NULL pointer deref

If we have one task trying to start the quota rescan worker while another

one is trying to disable quotas, we can end up hitting a race that results

in the quota rescan worker doing a NULL pointer dereference. The steps for

this are the following:

1) Quotas are enabled;

2) Task A calls the quota rescan ioctl and enters btrfs_qgroup_rescan().

It calls qgroup_rescan_init() which returns 0 (success) and then joins a

transaction and commits it;

3) Task B calls the quota disable ioctl and enters btrfs_quota_disable().

It clears the bit BTRFS_FS_QUOTA_ENABLED from fs_info->flags and calls

btrfs_qgroup_wait_for_completion(), which returns immediately since the

rescan worker is not yet running.

Then it starts a transaction and locks fs_info->qgroup_ioctl_lock;

4) Task A queues the rescan worker, by calling btrfs_queue_work();

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References