ext4: fix stack memory corruption with 64k block size

[ Upstream commit 30a9d7afe70ed6bd9191d3000e2ef1a34fb58493 ]

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: c9de560ded61f
Signed-off-by: Chandan Rajendra <chandan@linux.vnet.ibm.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: stable@vger.kernel.org
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index ad2fa476ce59ad5aa89d239579a47b3bb94af63f..e6798ca34928774eb5e59279960f04704e10f489 100644 (file)
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2254,7 +2254,7 @@ static int ext4_mb_seq_groups_show(struct seq_file *seq, void *v)
        struct ext4_group_info *grinfo;
        struct sg {
                struct ext4_group_info info;
-               ext4_grpblk_t counters[16];
+               ext4_grpblk_t counters[EXT4_MAX_BLOCK_LOG_SIZE + 2];
        } sg;
 
        group--;