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    PM / Hibernate: Fix free_unnecessary_pages() · 4d4cf23c
    Rafael J. Wysocki 提交于
    There is a bug in free_unnecessary_pages() that causes it to
    attempt to free too many pages in some cases, which triggers the
    BUG_ON() in memory_bm_clear_bit() for copy_bm.  Namely, if
    count_data_pages() is initially greater than alloc_normal, we get
    to_free_normal equal to 0 and "save" greater from 0.  In that case,
    if the sum of "save" and count_highmem_pages() is greater than
    alloc_highmem, we subtract a positive number from to_free_normal.
    Hence, since to_free_normal was 0 before the subtraction and is
    an unsigned int, the result is converted to a huge positive number
    that is used as the number of pages to free.
    
    Fix this bug by checking if to_free_normal is actually greater
    than or equal to the number we're going to subtract from it.
    Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
    Reported-and-tested-by: NMatthew Garrett <mjg@redhat.com>
    Cc: stable@kernel.org
    4d4cf23c
snapshot.c 59.9 KB