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| author | Andrey Ryabinin <aryabinin@virtuozzo.com> | 2019-06-14 17:31:49 +0300 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2019-06-14 16:37:30 +0200 |
| commit | f3176ec9420de0c385023afa3e4970129444ac2f (patch) | |
| tree | 4686a935b15da786848c46f9e5f41ffd326284b7 | |
| parent | 8d3289f2fa1e0c7e2f72c7352f1efb75d2ad7c76 (diff) | |
| download | lwn-f3176ec9420de0c385023afa3e4970129444ac2f.tar.gz lwn-f3176ec9420de0c385023afa3e4970129444ac2f.zip | |
x86/kasan: Fix boot with 5-level paging and KASAN
Since commit d52888aa2753 ("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 commit
12a8cc7fcf54 ("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 commit d52888aa2753 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 commit d52888aa2753
__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: 12a8cc7fcf54 ("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
| -rw-r--r-- | arch/x86/mm/kasan_init_64.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/mm/kasan_init_64.c b/arch/x86/mm/kasan_init_64.c index 8dc0fc0b1382..296da58f3013 100644 --- a/arch/x86/mm/kasan_init_64.c +++ b/arch/x86/mm/kasan_init_64.c @@ -199,7 +199,7 @@ static inline p4d_t *early_p4d_offset(pgd_t *pgd, unsigned long addr) if (!pgtable_l5_enabled()) return (p4d_t *)pgd; - p4d = __pa_nodebug(pgd_val(*pgd)) & PTE_PFN_MASK; + p4d = pgd_val(*pgd) & PTE_PFN_MASK; p4d += __START_KERNEL_map - phys_base; return (p4d_t *)p4d + p4d_index(addr); } |