[Devel] [PATCH 38/39] x86/kasan: Fix boot crash on AMD processors

[Andrey Ryabinin]

From: Andrey Ryabinin <a.ryabinin at samsung.com>

commit d4f86beacc21d538dc41e1fc75a22e084f547edf upstream.

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 at alien8.de>
Signed-off-by: Andrey Ryabinin <a.ryabinin at samsung.com>
Cc: <stable at vger.kernel.org> # 4.0+
Cc: Alexander Popov <alpopov at ptsecurity.com>
Cc: Alexander Potapenko <glider at google.com>
Cc: Andrey Konovalov <adech.fo at gmail.com>
Cc: Dmitry Vyukov <dvyukov at google.com>
Cc: Linus Torvalds <torvalds at linux-foundation.org>
Cc: Peter Zijlstra <peterz at infradead.org>
Cc: Thomas Gleixner <tglx at linutronix.de>
Link: http://lkml.kernel.org/r/1435828178-10975-5-git-send-email-a.ryabinin@samsung.com
Signed-off-by: Ingo Molnar <mingo at kernel.org>
Signed-off-by: Andrey Ryabinin <aryabinin at odin.com>
---
 arch/x86/mm/kasan_init_64.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/mm/kasan_init_64.c b/arch/x86/mm/kasan_init_64.c
index 0ada6cc..ef3dea9 100644
--- 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);
 	}
-- 
2.4.6