CVE-2024-46780

What it actually does

Race condition in nilfs2 sysfs attribute handlers that read superblock buffers without holding the ns_sem reader/writer semaphore, allowing concurrent modifications, swaps, or deallocation during resize or device degradation and resulting in invalid pointer dereferences or memory access violations.

Why it matters to the business

Systems using the nilfs2 filesystem may experience kernel instability, crashes, or unpredictable behavior during routine operations such as resizing or device errors, increasing operational risk for organizations with widespread Linux kernel deployments.

How an attack unfolds

An attacker with local access mounts a nilfs2 filesystem, then triggers concurrent sysfs reads of superblock attributes while initiating resize, repair, or backing-device failure scenarios that swap or invalidate the buffers, bypassing the required ns_sem exclusion and causing memory-safety violations.

How to fix it

Update the Linux kernel to commit b90beafac05931cbfcb6b1bd4f67c1923f47040e or later; apply the corresponding stable branch patches that enforce ns_sem protection around all superblock sysfs readers.

How to confirm the fix worked

Verify the running kernel contains commit b90beafac05931cbfcb6b1bd4f67c1923f47040e, confirm sysfs show methods for nilfs2 superblock attributes now acquire ns_sem, and test under concurrent resize and attribute read workloads for absence of memory faults.

Typical attack path

1. Mount nilfs2 filesystem on target system
2. Access exposed sysfs attributes for superblock parameters
3. Concurrently trigger filesystem resize, superblock modification, or backing device degradation
4. Cause ns_sem to be bypassed leading to invalid buffer access

How to detect it

Review kernel logs for oops, panic, or warning messages referencing nilfs2 superblock sysfs access without ns_sem; correlate with processes performing filesystem resize or attribute reads around the time of the event.

What your security team should do

• Apply the kernel fix immediately on all systems using nilfs2
• Audit environments for nilfs2 usage and prioritize patching where filesystem resizing or multi-device configurations are active
• Monitor for kernel oops or panic reports involving nilfs2 sysfs paths until patches are deployed