tee: add overflow check in register_shm_helper()

In the Linux kernel, the following vulnerability has been resolved:

tee: add overflow check in register_shm_helper()

With special lengths supplied by user space, register_shm_helper() has

an integer overflow when calculating the number of pages covered by a

supplied user space memory region.

This causes internal_get_user_pages_fast() a helper function of

pin_user_pages_fast() to do a NULL pointer dereference:

Unable to handle kernel NULL pointer dereference at virtual address 0000000000000010

Modules linked in:

CPU: 1 PID: 173 Comm: optee_example_a Not tainted 5.19.0 #11

Hardware name: QEMU QEMU Virtual Machine, BIOS 0.0.0 02/06/2015

pc : internal_get_user_pages_fast+0x474/0xa80

Call trace:

internal_get_user_pages_fast+0x474/0xa80

pin_user_pages_fast+0x24/0x4c

register_shm_helper+0x194/0x330

tee_shm_register_user_buf+0x78/0x120

tee_ioctl+0xd0/0x11a0

__arm64_sys_ioctl+0xa8/0xec

invoke_syscall+0x48/0x114

Fix this by adding an an explicit call to access_ok() in

tee_shm_register_user_buf() to catch an invalid user space address

early.