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    Subject[PATCH 3.16 114/233] drivers: char: mem: Fix wraparound check to allow mappings up to the end
    3.16.48-rc1 review patch.  If anyone has any objections, please let me know.

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

    From: Julius Werner <jwerner@chromium.org>

    commit 32829da54d9368103a2f03269a5120aa9ee4d5da upstream.

    A recent fix to /dev/mem prevents mappings from wrapping around the end
    of physical address space. However, the check was written in a way that
    also prevents a mapping reaching just up to the end of physical address
    space, which may be a valid use case (especially on 32-bit systems).
    This patch fixes it by checking the last mapped address (instead of the
    first address behind that) for overflow.

    Fixes: b299cde245 ("drivers: char: mem: Check for address space wraparound with mmap()")
    Reported-by: Nico Huber <nico.h@gmx.de>
    Signed-off-by: Julius Werner <jwerner@chromium.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    drivers/char/mem.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/drivers/char/mem.c
    +++ b/drivers/char/mem.c
    @@ -332,7 +332,7 @@ static int mmap_mem(struct file *file, s
    phys_addr_t offset = (phys_addr_t)vma->vm_pgoff << PAGE_SHIFT;

    /* It's illegal to wrap around the end of the physical address space. */
    - if (offset + (phys_addr_t)size < offset)
    + if (offset + (phys_addr_t)size - 1 < offset)
    return -EINVAL;

    if (!valid_mmap_phys_addr_range(vma->vm_pgoff, size))
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