From patchwork Mon Feb 20 22:41:24 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: FS: ext4: fix integer overflow in alloc_flex_gd() Date: Mon, 20 Feb 2012 12:41:24 -0000 From: Haogang Chen X-Patchwork-Id: 142200 Message-Id: <1329777684-18396-1-git-send-email-haogangchen@gmail.com> To: Theodore Tso , Andreas Dilger , linux-ext4@vger.kernel.org Cc: linux-kernel@vger.kernel.org, haogangchen@gmail.com 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. Signed-off-by: Haogang Chen Reviewed-by: Eric Sandeen --- fs/ext4/resize.c | 2 ++ 1 files changed, 2 insertions(+), 0 deletions(-) diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c index f9d948f..8601f4b 100644 --- a/fs/ext4/resize.c +++ b/fs/ext4/resize.c @@ -161,6 +161,8 @@ static struct ext4_new_flex_group_data *alloc_flex_gd(unsigned long flexbg_size) if (flex_gd == NULL) goto out3; + if (flexbg_size >= UINT_MAX / sizeof(struct ext4_new_flex_group_data)) + goto out2; flex_gd->count = flexbg_size; flex_gd->groups = kmalloc(sizeof(struct ext4_new_group_data) *