From: Chandan Rajendra <chandan@linux.vnet.ibm.com>
Date: Tue, 15 Nov 2016 02:26:26 +0000 (-0500)
Subject: ext4: fix stack memory corruption with 64k block size
X-Git-Tag: v4.10-rc1~130^2~45
X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=30a9d7afe70ed6bd9191d3000e2ef1a34fb58493;p=linux.git

ext4: fix stack memory corruption with 64k block size

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
---

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index a937ac7ef99f..7ae43c59bc79 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2287,7 +2287,7 @@ 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--;