Executive brief
The Linux kernel's network filesystem (netfs) layer contains a race condition in write request handling that can cause cache operations to be skipped when asynchronous cache initialization is in progress. This could lead to data consistency issues, cache bypass scenarios, or potential data loss in systems relying on network filesystem caching for data durability and performance.
Technical details
The vulnerability is a race condition in the `netfs_create_write_req()` function in `fs/netfs/write_issue.c`. The function checks if the fscache cookie is disabled before calling `fscache_begin_write_operation()`, but this check fails to account for asynchronous cache object creation that may not yet have completed. When the check runs while async initialization is still in progress, the function incorrectly skips caching operations. The fix removes the premature cookie-state check and delegates validation to `fscache_begin_write_operation()` itself. The vulnerability affects Linux kernel network filesystem code paths and is triggered during write request processing; no special authentication or user interaction is required beyond normal filesystem write operations.
Affected products
- Linux Linux kernel multiple versions from 2.6 through 6.x and beyond
Timeline
- 2026-08-15: disclosed: Published in NVD
- 2026-06-25: patched: Upstream commit dbd6f56d975b23241b7bbb11bb8f562af548a0aa by David Howells