From 967ac8af4475ce45474800709b12137aa7634c77 Mon Sep 17 00:00:00 2001
From: Haogang Chen <haogangchen@gmail.com>
Date: Mon, 28 May 2012 14:21:55 -0400
Subject: [PATCH] ext4: fix potential integer overflow in alloc_flex_gd()

In alloc_flex_gd(), when flexbg_size is large, kmalloc size would
overflow and flex_gd->groups would point to a buffer smaller than
expected, causing OOB accesses when it is used.

Note that in ext4_resize_fs(), flexbg_size is calculated using
sbi->s_log_groups_per_flex, which is read from the disk and only bounded
to [1, 31]. The patch returns NULL for too large flexbg_size.

Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Haogang Chen <haogangchen@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@kernel.org
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