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    Subject[tip:x86/urgent] x86/kasan: Fix boot crash on AMD processors
    Commit-ID:  d4f86beacc21d538dc41e1fc75a22e084f547edf
    Gitweb: http://git.kernel.org/tip/d4f86beacc21d538dc41e1fc75a22e084f547edf
    Author: Andrey Ryabinin <a.ryabinin@samsung.com>
    AuthorDate: Thu, 2 Jul 2015 12:09:36 +0300
    Committer: Ingo Molnar <mingo@kernel.org>
    CommitDate: Mon, 6 Jul 2015 14:53:14 +0200

    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>
    ---
    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 5d26642..9a54dbe 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);
    }

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