Linux kernel struct file pointer

Question

Is it guaranteed that a struct file pointer won't be deallocated and reallocated somewhere else in memory during its open to close lifecycle?

I want to uniquely identify file structs that are passed to a device driver (through read/write/open etc) and was wondering if I could just use the pointer to the file struct for identification. The only other alternative I see would be to store a unique identifier in private_data, if it is not guaranteed that the struct file pointer will not change.

Answer 1

Nothing will happen to the pointer. But you have to make sure that if this pointer is being passed across the kernel-user boundary (or computer-network), you actually check that the pointer you get is one of the valid pointers and perhaps an appropriate one (expected from this particular caller, if you can identify them). Otherwise you will have a huge security hole.