linux-kernel - [PATCH 3.16 035/370] ext4: fix stack memory corruption with 64k block size

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Message-ID: <lsq.1489146382.294629642@decadent.org.uk>
Date:   Fri, 10 Mar 2017 11:46:22 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Chandan Rajendra" <chandan@...ux.vnet.ibm.com>,
        "Jan Kara" <jack@...e.cz>, "Theodore Ts'o" <tytso@....edu>
Subject: [PATCH 3.16 035/370] ext4: fix stack memory corruption with 64k
 block size

3.16.42-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Chandan Rajendra <chandan@...ux.vnet.ibm.com>

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@...ux.vnet.ibm.com>
Signed-off-by: Theodore Ts'o <tytso@....edu>
Reviewed-by: Jan Kara <jack@...e.cz>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 fs/ext4/mballoc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2252,7 +2252,7 @@ static int ext4_mb_seq_groups_show(struc
 	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--;