VMCI: check context->notify_page after call to get_user_pages_fast() to avoid GPF

In the Linux kernel, the following vulnerability has been resolved: VMCI: check context->notify_page after call to get_user_pages_fast() to avoid GPF The call to get_user_pages_fast() in vmci_host_setup_notify() can return NULL context->notify_page causing a GPF. To avoid GPF check if context->notify_page == NULL and return error if so. general protection fault, probably for non-canonical address 0xe0009d1000000060: 0000 [#1] PREEMPT SMP KASAN NOPTI KASAN: maybe wild-memory-access in range [0x0005088000000300- 0x0005088000000307] CPU: 2 PID: 26180 Comm: repro_34802241 Not tainted 6.1.0-rc4 #1 Hardware name: Red Hat KVM, BIOS 1.15.0-2.module+el8.6.0 04/01/2014 RIP: 0010:vmci_ctx_check_signal_notify+0x91/0xe0 Call Trace: <TASK> vmci_host_unlocked_ioctl+0x362/0x1f40 __x64_sys_ioctl+0x1a1/0x230 do_syscall_64+0x3a/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd