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: v3.2.87~186
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ede1905be38b46ece20bf4b5af11080863b85a6a;p=pandora-kernel.git

ext4: fix stack memory corruption with 64k block size

commit 30a9d7afe70ed6bd9191d3000e2ef1a34fb58493 upstream.

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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 3338f353687f..ebc50aa7347c 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2134,7 +2134,7 @@ static int ext4_mb_seq_groups_show(struct seq_file *seq, void *v)
 	struct ext4_buddy e4b;
 	struct sg {
 		struct ext4_group_info info;
-		ext4_grpblk_t counters[16];
+		ext4_grpblk_t counters[EXT4_MAX_BLOCK_LOG_SIZE + 2];
 	} sg;
 
 	group--;