• Johannes Thumshirn's avatar
    btrfs: ensure that a DUP or RAID1 block group has exactly two stripes · 349ae63f
    Johannes Thumshirn authored
    We recently had a customer issue with a corrupted filesystem. When
    trying to mount this image btrfs panicked with a division by zero in
    calc_stripe_length().
    
    The corrupt chunk had a 'num_stripes' value of 1. calc_stripe_length()
    takes this value and divides it by the number of copies the RAID profile
    is expected to have to calculate the amount of data stripes. As a DUP
    profile is expected to have 2 copies this division resulted in 1/2 = 0.
    Later then the 'data_stripes' variable is used as a divisor in the
    stripe length calculation which results in a division by 0 and thus a
    kernel panic.
    
    When encountering a filesystem with a DUP block group and a
    'num_stripes' value unequal to 2, refuse mounting as the image is
    corrupted and will lead to unexpected behaviour.
    
    Code inspection showed a RAID1 block group has the same issues.
    
    Fixes: e06cd3dd ("Btrfs: add validadtion checks for chunk loading")
    CC: stable@vger.kernel.org # 4.4+
    Reviewed-by: default avatarQu Wenruo <wqu@suse.com>
    Reviewed-by: default avatarNikolay Borisov <nborisov@suse.com>
    Signed-off-by: default avatarJohannes Thumshirn <jthumshirn@suse.de>
    Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
    Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
    349ae63f
volumes.c 210 KB