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    Subject[PATCH 4.9 180/329] ia64/err-inject: Use get_user_pages_fast()
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

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

    From: Davidlohr Bueso <dave@stgolabs.net>

    [ Upstream commit 69c907022a7d9325cdc5c9dd064571e445df9a47 ]

    At the point of sysfs callback, the call to gup is
    done without mmap_sem (or any lock for that matter).
    This is racy. As such, use the get_user_pages_fast()
    alternative and safely avoid taking the lock, if possible.

    Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
    Signed-off-by: Tony Luck <tony.luck@intel.com>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    arch/ia64/kernel/err_inject.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/arch/ia64/kernel/err_inject.c
    +++ b/arch/ia64/kernel/err_inject.c
    @@ -142,7 +142,7 @@ store_virtual_to_phys(struct device *dev
    u64 virt_addr=simple_strtoull(buf, NULL, 16);
    int ret;

    - ret = get_user_pages(virt_addr, 1, FOLL_WRITE, NULL, NULL);
    + ret = get_user_pages_fast(virt_addr, 1, FOLL_WRITE, NULL);
    if (ret<=0) {
    #ifdef ERR_INJ_DEBUG
    printk("Virtual address %lx is not existing.\n",virt_addr);

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