CVE-2022-49655 Information

Description

In the Linux kernel the following vulnerability has been resolved:

fscache: Fix invalidation/lookup race

If an NFS file is opened for writing and closed fscache_invalidate() will be asked to invalidate the file - however if the cookie is in the LOOKING_UP state (or the CREATING state) then request to invalidate doesn’t get recorded for fscache_cookie_state_machine() to do something with.

Fix this by making __fscache_invalidate() set a flag if it sees the cookie is in the LOOKING_UP state to indicate that we need to go to invalidation. Note that this requires a count on the n_accesses counter for the state machine which that will release when it’s done.

fscache_cookie_state_machine() then shifts to the INVALIDATING state if it sees the flag.

Without this an nfs file can get corrupted if it gets modified locally and then read locally as the cache contents may not get updated.

Reference

https://git.kernel.org/stable/c/85e4ea1049c70fb99de5c6057e835d151fb647da https://git.kernel.org/stable/c/b1ae9f617f8a5c848d9205b8e228c6f0d1af754b