Patch "x86/kasan: Fix boot crash on AMD processors" has been added to the 4.1-stable tree

This is a note to let you know that I've just added the patch titled

x86/kasan: Fix boot crash on AMD processors

to the 4.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
x86-kasan-fix-boot-crash-on-amd-processors.patch
and it can be found in the queue-4.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Andrey Ryabinin <[email protected]>
Date: Thu, 2 Jul 2015 12:09:36 +0300
Subject: x86/kasan: Fix boot crash on AMD processors

From: Andrey Ryabinin <[email protected]>

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.

---
 arch/x86/mm/kasan_init_64.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

@@ -85,7 +85,7 @@ static int __init zero_pmd_populate(pud_
 	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_
 	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(unsi
 	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);
 	}

Patches currently in stable-queue which might be from [email protected] are

queue-4.1/x86-kasan-fix-kasan-shadow-region-page-tables.patch queue-4.1/x86-kasan-fix-boot-crash-on-amd-processors.patch queue-4.1/x86-init-clear-init_level4_pgt-earlier.patch queue-4.1/x86-kasan-flush-tlbs-after-switching-cr3.patch