[ 3.5.y.z extended stable ] Patch "ext4: fix overflow when counting used blocks on 32-bit" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    ext4: fix overflow when counting used blocks on 32-bit

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From ae88846d80236dc945aad8eef9b4141fe34bbce7 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack at suse.cz>
Date: Fri, 31 May 2013 19:39:56 -0400
Subject: [PATCH] ext4: fix overflow when counting used blocks on 32-bit
 architectures

commit 8af8eecc1331dbf5e8c662022272cf667e213da5 upstream.

The arithmetics adding delalloc blocks to the number of used blocks in
ext4_getattr() can easily overflow on 32-bit archs as we first multiply
number of blocks by blocksize and then divide back by 512. Make the
arithmetics more clever and also use proper type (unsigned long long
instead of unsigned long).

Signed-off-by: Jan Kara <jack at suse.cz>
Signed-off-by: Theodore Ts'o <tytso at mit.edu>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 fs/ext4/inode.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 55006fa..8aacdda 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4317,7 +4317,7 @@ int ext4_getattr(struct vfsmount *mnt, struct dentry *dentry,
 		 struct kstat *stat)
 {
 	struct inode *inode;
-	unsigned long delalloc_blocks;
+	unsigned long long delalloc_blocks;

 	inode = dentry->d_inode;
 	generic_fillattr(inode, stat);
@@ -4335,7 +4335,7 @@ int ext4_getattr(struct vfsmount *mnt, struct dentry *dentry,
 	delalloc_blocks = EXT4_C2B(EXT4_SB(inode->i_sb),
 				EXT4_I(inode)->i_reserved_data_blocks);

-	stat->blocks += (delalloc_blocks << inode->i_sb->s_blocksize_bits)>>9;
+	stat->blocks += delalloc_blocks << (inode->i_sb->s_blocksize_bits-9);
 	return 0;
 }

--
1.8.1.2