| 1 | // SPDX-License-Identifier: GPL-2.0-only |
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| 2 | |
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| 3 | #include <linux/uaccess.h> |
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| 4 | #include <linux/kernel.h> |
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| 5 | |
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| 6 | #include <asm/vsyscall.h> |
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| 7 | |
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| 8 | #ifdef CONFIG_X86_64 |
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| 9 | bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size) |
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| 10 | { |
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| 11 | unsigned long vaddr = (unsigned long)unsafe_src; |
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| 12 | |
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| 13 | /* |
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| 14 | * Do not allow userspace addresses. This disallows |
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| 15 | * normal userspace and the userspace guard page: |
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| 16 | */ |
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| 17 | if (vaddr < TASK_SIZE_MAX + PAGE_SIZE) |
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| 18 | return false; |
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| 19 | |
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| 20 | /* |
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| 21 | * Reading from the vsyscall page may cause an unhandled fault in |
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| 22 | * certain cases. Though it is at an address above TASK_SIZE_MAX, it is |
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| 23 | * usually considered as a user space address. |
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| 24 | */ |
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| 25 | if (is_vsyscall_vaddr(vaddr)) |
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| 26 | return false; |
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| 27 | |
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| 28 | /* |
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| 29 | * Allow everything during early boot before 'x86_virt_bits' |
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| 30 | * is initialized. Needed for instruction decoding in early |
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| 31 | * exception handlers. |
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| 32 | */ |
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| 33 | if (!boot_cpu_data.x86_virt_bits) |
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| 34 | return true; |
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| 35 | |
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| 36 | return __is_canonical_address(vaddr, vaddr_bits: boot_cpu_data.x86_virt_bits); |
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| 37 | } |
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| 38 | #else |
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| 39 | bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size) |
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| 40 | { |
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| 41 | return (unsigned long)unsafe_src >= TASK_SIZE_MAX; |
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| 42 | } |
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| 43 | #endif |
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| 44 | |
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