Bug 2396384 (CVE-2022-50379)

Summary: CVE-2022-50379 kernel: Linux kernel (btrfs): Use-after-free vulnerability leads to Denial of Service
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: low    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's btrfs filesystem. A race condition during quota enablement can lead to a use-after-free vulnerability. This occurs when the quota rescan worker fails to initialize, causing a freed memory region to be improperly referenced. A local user could exploit this to trigger a system crash, resulting in a Denial of Service (DoS).
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Description OSIDB Bzimport 2025-09-18 14:01:56 UTC 
In the Linux kernel, the following vulnerability has been resolved:

btrfs: fix race between quota enable and quota rescan ioctl

When enabling quotas, at btrfs_quota_enable(), after committing the
transaction, we change fs_info->quota_root to point to the quota root we
created and set BTRFS_FS_QUOTA_ENABLED at fs_info->flags. Then we try
to start the qgroup rescan worker, first by initializing it with a call
to qgroup_rescan_init() - however if that fails we end up freeing the
quota root but we leave fs_info->quota_root still pointing to it, this
can later result in a use-after-free somewhere else.

We have previously set the flags BTRFS_FS_QUOTA_ENABLED and
BTRFS_QGROUP_STATUS_FLAG_ON, so we can only fail with -EINPROGRESS at
btrfs_quota_enable(), which is possible if someone already called the
quota rescan ioctl, and therefore started the rescan worker.

So fix this by ignoring an -EINPROGRESS and asserting we can't get any
other error.
Comment 1 Keith Grant 2025-09-18 15:05:52 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025091851-CVE-2022-50379-a7c6@gregkh/T