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f79936545f
Previously, if copy_from_kernel_nofault() was called before
boot_cpu_data.x86_virt_bits was set up, then it would trigger undefined
behavior due to a shift by 64.
This ended up causing boot failures in the latest version of ubuntu2204
in the gcp project when using SEV-SNP.
Specifically, this function is called during an early #VC handler which
is triggered by a CPUID to check if NX is implemented.
Fixes: 1aa9aa8ee5 ("x86/sev-es: Setup GHCB-based boot #VC handler")
Suggested-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Adam Dunlap <acdunlap@google.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Jacob Xu <jacobhxu@google.com>
Link: https://lore.kernel.org/r/20230912002703.3924521-2-acdunlap@google.com
33 lines
838 B
C
33 lines
838 B
C
// 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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#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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* 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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