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    Subject[PATCH 5.0 095/238] btrfs: ensure that a DUP or RAID1 block group has exactly two stripes
    Date
    5.0-stable review patch.  If anyone has any objections, please let me know.

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

    From: Johannes Thumshirn <jthumshirn@suse.de>

    commit 349ae63f40638a28c6fce52e8447c2d14b84cc0c upstream.

    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: e06cd3dd7cea ("Btrfs: add validadtion checks for chunk loading")
    CC: stable@vger.kernel.org # 4.4+
    Reviewed-by: Qu Wenruo <wqu@suse.com>
    Reviewed-by: Nikolay Borisov <nborisov@suse.com>
    Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
    Reviewed-by: David Sterba <dsterba@suse.com>
    Signed-off-by: David Sterba <dsterba@suse.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/btrfs/volumes.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    --- a/fs/btrfs/volumes.c
    +++ b/fs/btrfs/volumes.c
    @@ -6782,10 +6782,10 @@ static int btrfs_check_chunk_valid(struc
    }

    if ((type & BTRFS_BLOCK_GROUP_RAID10 && sub_stripes != 2) ||
    - (type & BTRFS_BLOCK_GROUP_RAID1 && num_stripes < 1) ||
    + (type & BTRFS_BLOCK_GROUP_RAID1 && num_stripes != 2) ||
    (type & BTRFS_BLOCK_GROUP_RAID5 && num_stripes < 2) ||
    (type & BTRFS_BLOCK_GROUP_RAID6 && num_stripes < 3) ||
    - (type & BTRFS_BLOCK_GROUP_DUP && num_stripes > 2) ||
    + (type & BTRFS_BLOCK_GROUP_DUP && num_stripes != 2) ||
    ((type & BTRFS_BLOCK_GROUP_PROFILE_MASK) == 0 &&
    num_stripes != 1)) {
    btrfs_err(fs_info,

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