Linux Kernel fscache Invalidation Lookup Race Vulnerability

A vulnerability in the Linux kernel's fscache mechanism can lead to NFS file corruption. When an NFS file opened for writing is closed, the fscache_invalidate() function is called to invalidate the file. However, if the associated cookie is in the LOOKING_UP or CREATING state, the invalidation request is not properly recorded for the fscache_cookie_state_machine() to process. This oversight can cause cache contents to become outdated, allowing locally modified files to be incorrectly read, as the cached data may not reflect recent changes.

Impact

This vulnerability can cause NFS files to become corrupted by allowing outdated cache contents to be read, despite local modifications not being properly reflected.