x86/kasan: Fix boot crash on AMD processors

While populating zero shadow wrong bits in upper level page
tables used. __PAGE_KERNEL_RO that was used for pgd/pud/pmd has
_PAGE_BIT_GLOBAL set. Global bit is present only in the lowest
level of the page translation hierarchy (ptes), and it should be
zero in upper levels.

This bug seems doesn't cause any troubles on Intel cpus, while
on AMDs it cause kernel crash on boot.

Use _KERNPG_TABLE bits for pgds/puds/pmds to fix this.

Reported-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>
Cc: <stable@vger.kernel.org> # 4.0+
Cc: Alexander Popov <alpopov@ptsecurity.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <adech.fo@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1435828178-10975-5-git-send-email-a.ryabinin@samsung.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/mm/kasan_init_64.c b/arch/x86/mm/kasan_init_64.c
index 5d26642e4e8a03a1852d46dcc1ae63c0e90affab..9a54dbe980643a41d2ba3dbd9c57db2fdc779a8d 100644 (file)
--- a/arch/x86/mm/kasan_init_64.c
+++ b/arch/x86/mm/kasan_init_64.c
@@ -85,7 +85,7 @@ static int __init zero_pmd_populate(pud_t *pud, unsigned long addr,
        while (IS_ALIGNED(addr, PMD_SIZE) && addr + PMD_SIZE <= end) {
                WARN_ON(!pmd_none(*pmd));
                set_pmd(pmd, __pmd(__pa_nodebug(kasan_zero_pte)
-                                       | __PAGE_KERNEL_RO));
+                                       | _KERNPG_TABLE));
                addr += PMD_SIZE;
                pmd = pmd_offset(pud, addr);
        }
@@ -111,7 +111,7 @@ static int __init zero_pud_populate(pgd_t *pgd, unsigned long addr,
        while (IS_ALIGNED(addr, PUD_SIZE) && addr + PUD_SIZE <= end) {
                WARN_ON(!pud_none(*pud));
                set_pud(pud, __pud(__pa_nodebug(kasan_zero_pmd)
-                                       | __PAGE_KERNEL_RO));
+                                       | _KERNPG_TABLE));
                addr += PUD_SIZE;
                pud = pud_offset(pgd, addr);
        }
@@ -136,7 +136,7 @@ static int __init zero_pgd_populate(unsigned long addr, unsigned long end)
        while (IS_ALIGNED(addr, PGDIR_SIZE) && addr + PGDIR_SIZE <= end) {
                WARN_ON(!pgd_none(*pgd));
                set_pgd(pgd, __pgd(__pa_nodebug(kasan_zero_pud)
-                                       | __PAGE_KERNEL_RO));
+                                       | _KERNPG_TABLE));
                addr += PGDIR_SIZE;
                pgd = pgd_offset_k(addr);
        }