diff options
| author | Andrey Ryabinin <aryabinin@virtuozzo.com> | 2019-06-14 17:31:49 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-06-19 08:21:00 +0200 |
| commit | 488beeebddaf563aed96c27aa78c520a00f1a30f (patch) | |
| tree | b6a98a490e127f4bfccd68cecd92b2b475487f47 /arch | |
| parent | 9e7018426849aebaddbd48fe5d16727ead98f711 (diff) | |
x86/kasan: Fix boot with 5-level paging and KASAN
commit f3176ec9420de0c385023afa3e4970129444ac2f upstream.
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
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch')
| -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 af6f2f9c6a26..5813950b5877 100644 --- a/arch/x86/mm/kasan_init_64.c +++ b/arch/x86/mm/kasan_init_64.c @@ -194,7 +194,7 @@ static inline p4d_t *early_p4d_offset(pgd_t *pgd, unsigned long addr) if (!IS_ENABLED(CONFIG_X86_5LEVEL)) 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); } |