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    Subject[patch 21/29] x86: NX bit handling in change_page_attr()
    2.6.23-stable review patch.  If anyone has any objections, please let us
    know.

    ------------------
    From: Huang, Ying <ying.huang@intel.com>

    patch 84e0fdb1754d066dd0a8b257de7299f392d1e727 in mainline.

    x86: NX bit handling in change_page_attr()

    This patch fixes a bug of change_page_attr/change_page_attr_addr on
    Intel x86_64 CPUs. After changing page attribute to be executable with
    these functions, the page remains un-executable on Intel x86_64 CPU.
    Because on Intel x86_64 CPU, only if the "NX" bits of all four level
    page tables are cleared, the corresponding page is executable (refer to
    section 4.13.2 of Intel 64 and IA-32 Architectures Software Developer's
    Manual). So, the bug is fixed through clearing the "NX" bit of PMD when
    splitting the huge PMD.

    Signed-off-by: Huang Ying <ying.huang@intel.com>
    Cc: Andi Kleen <ak@suse.de>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    arch/x86_64/mm/pageattr.c | 1 +
    1 file changed, 1 insertion(+)

    --- a/arch/x86_64/mm/pageattr.c
    +++ b/arch/x86_64/mm/pageattr.c
    @@ -148,6 +148,7 @@ __change_page_attr(unsigned long address
    split = split_large_page(address, prot, ref_prot2);
    if (!split)
    return -ENOMEM;
    + pgprot_val(ref_prot2) &= ~_PAGE_NX;
    set_pte(kpte, mk_pte(split, ref_prot2));
    kpte_page = split;
    }
    --
    -
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