| // SPDX-License-Identifier: GPL-2.0-only |
| |
| #include <linux/uaccess.h> |
| #include <linux/kernel.h> |
| |
| #include <asm/vsyscall.h> |
| |
| #ifdef CONFIG_X86_64 |
| bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size) |
| { |
| unsigned long vaddr = (unsigned long)unsafe_src; |
| |
| /* |
| * Do not allow userspace addresses. This disallows |
| * normal userspace and the userspace guard page: |
| */ |
| if (vaddr < TASK_SIZE_MAX + PAGE_SIZE) |
| return false; |
| |
| /* |
| * Reading from the vsyscall page may cause an unhandled fault in |
| * certain cases. Though it is at an address above TASK_SIZE_MAX, it is |
| * usually considered as a user space address. |
| */ |
| if (is_vsyscall_vaddr(vaddr)) |
| return false; |
| |
| /* |
| * Allow everything during early boot before 'x86_virt_bits' |
| * is initialized. Needed for instruction decoding in early |
| * exception handlers. |
| */ |
| if (!boot_cpu_data.x86_virt_bits) |
| return true; |
| |
| return __is_canonical_address(vaddr, boot_cpu_data.x86_virt_bits); |
| } |
| #else |
| bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size) |
| { |
| return (unsigned long)unsafe_src >= TASK_SIZE_MAX; |
| } |
| #endif |
