mirror of https://gitee.com/openkylin/linux.git
x86/kasan: Fix boot with 5-level paging and KASAN
Since commitd52888aa27
("x86/mm: Move LDT remap out of KASLR region on 5-level paging") kernel doesn't boot with KASAN on 5-level paging machines. The bug is actually in early_p4d_offset() and introduced by commit12a8cc7fcf
("x86/kasan: Use the same shadow offset for 4- and 5-level paging") early_p4d_offset() tries to convert pgd_val(*pgd) value to a physical address. This doesn't make sense because pgd_val() already contains the physical address. It did work prior to commitd52888aa27
because the result of "__pa_nodebug(pgd_val(*pgd)) & PTE_PFN_MASK" was the same as "pgd_val(*pgd) & PTE_PFN_MASK". __pa_nodebug() just set some high bits which were masked out by applying PTE_PFN_MASK. After the change of the PAGE_OFFSET offset in commitd52888aa27
__pa_nodebug(pgd_val(*pgd)) started to return a value with more high bits set and PTE_PFN_MASK wasn't enough to mask out all of them. So it returns a wrong not even canonical address and crashes on the attempt to dereference it. Switch back to pgd_val() & PTE_PFN_MASK to cure the issue. Fixes:12a8cc7fcf
("x86/kasan: Use the same shadow offset for 4- and 5-level paging") Reported-by: Kirill A. Shutemov <kirill@shutemov.name> Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Borislav Petkov <bp@alien8.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Alexander Potapenko <glider@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: kasan-dev@googlegroups.com Cc: stable@vger.kernel.org Cc: <stable@vger.kernel.org> Link: https://lkml.kernel.org/r/20190614143149.2227-1-aryabinin@virtuozzo.com
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@ -199,7 +199,7 @@ static inline p4d_t *early_p4d_offset(pgd_t *pgd, unsigned long addr)
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if (!pgtable_l5_enabled())
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return (p4d_t *)pgd;
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p4d = __pa_nodebug(pgd_val(*pgd)) & PTE_PFN_MASK;
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p4d = pgd_val(*pgd) & PTE_PFN_MASK;
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p4d += __START_KERNEL_map - phys_base;
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return (p4d_t *)p4d + p4d_index(addr);
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}
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