CVE-2025-38393

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

NFSv4/pNFS: Fix a race to wake on NFS_LAYOUT_DRAIN

We found a few different systems hung up in writeback waiting on the same page lock, and one task waiting on the NFS_LAYOUT_DRAIN bit in pnfs_update_layout(), however the pnfs_layout_hdr's plh_outstanding count was zero.

It seems most likely that this is another race between the waiter and waker similar to commit ed0172af5d6f ("SUNRPC: Fix a race to wake a sync task"). Fix it up by applying the advised barrier.

This vulnerability is rated as Moderate because triggering it depends on winning a specific race condition during asynchronous writeback on NFSv4 mounts utilizing parallel NFS (pNFS), with the impact restricted to a denial of service. The flaw cannot be leveraged for privilege escalation or unauthorized data disclosure. Systems are only susceptible if they actively mount remote shares using pNFS layouts, meaning configurations relying on traditional NFS or local storage remain unaffected.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.