CVE-2024-27058

What it actually does

Race condition in tmpfs dquot rbtree handling allows concurrent modification of the tree root without consistent dqio_sem protection, causing shmem_release_dquot to search from an invalid location after a rebalance and trigger a warning.

Why it matters to the business

Kernel warnings or potential instability in tmpfs environments handling disk quotas, increasing operational overhead for systems using shared memory with quotas; low immediate risk but requires patching across Linux deployments.

How an attack unfolds

An attacker triggers concurrent shmem acquire/release dquot operations; one thread fetches the tree root unprotected while another acquires the semaphore, rebalances the tree, and releases it, causing the first thread to miss the node and log a warning upon acquiring the lock.

How to fix it

Update the Linux kernel to a version containing commit c7077f43f30d817d10a9f8245e51576ac114b2f0 or later; rebuild and deploy updated kernels on affected systems.

How to confirm the fix worked

Confirm kernel source includes the referenced commit; test concurrent dquot operations on tmpfs mounts to verify absence of the race warning; monitor for stable rb_tree root handling under load.

Typical attack path

1. Identify tmpfs mounts with dquot enabled
2. Spawn concurrent threads performing shmem acquire and release dquot operations
3. Time operations to race on rb_tree root fetch versus rebalance under dqio_sem
4. Trigger warning in shmem_release_dquot due to missed node search

How to detect it

Search kernel logs for shmem_release_dquot warnings referencing missing rbtree nodes; inspect for concurrent tmpfs dquot activity patterns around the time of any warnings.

What your security team should do

• Prioritize kernel updates on systems using tmpfs with disk quotas
• Review tmpfs configurations for unnecessary quota usage until patched
• Monitor kernel logs for related warnings post-update