CVE-2024-40935 Information

Description

In the Linux kernel the following vulnerability has been resolved:

cachefiles: flush all requests after setting CACHEFILES_DEAD

In ondemand mode when the daemon is processing an open request if the kernel flags the cache as CACHEFILES_DEAD the cachefiles_daemon_write() will always return -EIO so the daemon can’t pass the copen to the kernel. Then the kernel process that is waiting for the copen triggers a hung_task.

Since the DEAD state is irreversible it can only be exited by closing /dev/cachefiles. Therefore after calling cachefiles_io_error() to mark the cache as CACHEFILES_DEAD if in ondemand mode flush all requests to avoid the above hungtask. We may still be able to read some of the cached data before closing the fd of /dev/cachefiles.

Note that this relies on the patch that adds reference counting to the req otherwise it may UAF.

Reference

https://git.kernel.org/stable/c/320ba9cbca78be79c912143bbba1d1b35ca55cf0 https://git.kernel.org/stable/c/3bf0b8030296e9ee60d3d4c15849ad9ac0b47081 https://git.kernel.org/stable/c/e73fac95084839c5178d97e81c6a2051251bdc00 https://git.kernel.org/stable/c/85e833cd7243bda7285492b0653c3abb1e2e757b