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    Subject[PATCH 4.10 69/75] x86, mm: fix gup_pte_range() vs DAX mappings
    Date
    4.10-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Dan Williams <dan.j.williams@intel.com>

    commit ef947b2529f918d9606533eb9c32b187ed6a5ede upstream.

    gup_pte_range() fails to check pte_allows_gup() before translating a DAX
    pte entry, pte_devmap(), to a page. This allows writes to read-only
    mappings, and bypasses the DAX cacheline dirty tracking due to missed
    'mkwrite' faults. The gup_huge_pmd() path and the gup_huge_pud() path
    correctly check pte_allows_gup() before checking for _devmap() entries.

    Fixes: 3565fce3a659 ("mm, x86: get_user_pages() for dax mappings")
    Link: http://lkml.kernel.org/r/148804251312.36605.12665024794196605053.stgit@dwillia2-desk3.amr.corp.intel.com
    Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
    Signed-off-by: Dan Williams <dan.j.williams@intel.com>
    Reported-by: Dave Hansen <dave.hansen@linux.intel.com>
    Reported-by: Ross Zwisler <ross.zwisler@linux.intel.com>
    Cc: Xiong Zhou <xzhou@redhat.com>
    Cc: Ingo Molnar <mingo@redhat.com>
    Cc: "H. Peter Anvin" <hpa@zytor.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/x86/mm/gup.c | 8 ++++++--
    1 file changed, 6 insertions(+), 2 deletions(-)

    --- a/arch/x86/mm/gup.c
    +++ b/arch/x86/mm/gup.c
    @@ -120,6 +120,11 @@ static noinline int gup_pte_range(pmd_t
    return 0;
    }

    + if (!pte_allows_gup(pte_val(pte), write)) {
    + pte_unmap(ptep);
    + return 0;
    + }
    +
    if (pte_devmap(pte)) {
    pgmap = get_dev_pagemap(pte_pfn(pte), pgmap);
    if (unlikely(!pgmap)) {
    @@ -127,8 +132,7 @@ static noinline int gup_pte_range(pmd_t
    pte_unmap(ptep);
    return 0;
    }
    - } else if (!pte_allows_gup(pte_val(pte), write) ||
    - pte_special(pte)) {
    + } else if (pte_special(pte)) {
    pte_unmap(ptep);
    return 0;
    }

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