The number of 'counters' elements needed in 'struct sg' is
super_block->s_blocksize_bits + 2. Presently we have 16 'counters'
elements in the array. This is insufficient for block sizes >= 32k. In
such cases the memcpy operation performed in ext4_mb_seq_groups_show()
would cause stack memory corruption.

Fixes: c9de560dSigned-off-by: NChandan Rajendra <chandan@linux.vnet.ibm.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>
Reviewed-by: NJan Kara <jack@suse.cz>
Cc: stable@vger.kernel.org