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