In the Linux kernel, the following vulnerability has been resolved: cachefiles: Fix NULL pointer dereference in object->file At present, the object->file has the NULL pointer dereference problem in ondemand-mode. The root cause is that the allocated fd and object->file lifetime are inconsistent, and the user-space invocation to anonfd uses object->file. Following is the process that triggers the issue: [write fd] [umount] cachefilesondemandfdwriteiter fscachecookiestatemachine cachefileswithdrawcookie if (!file) return -ENOBUFS cachefilescleanupobject cachefilesunmarkinodeinuse fput(object->file) object->file = NULL // file NULL pointer dereference! _cachefiles_write(..., file, ...) Fix this issue by add an additional reference count to the object->file before write/llseek, and decrement after it finished.