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: v3.12.70~207
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c4c0dbd27c8f3c775b65a8bf75dd2e0aee6d1160;p=thirdparty%2Fkernel%2Fstable.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: Jiri Slaby <jslaby@suse.cz>
---

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index d775b7b02dd0a..2b4ed2bf9569a 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2243,7 +2243,7 @@ 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--;