Patchwork [085/145] ext4: fix overflow when counting used blocks on 32-bit architectures

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Submitter Kamal Mostafa
Date July 17, 2013, 10:46 p.m.
Message ID <1374101277-7915-86-git-send-email-kamal@canonical.com>
Download mbox | patch
Permalink /patch/259851/
State New
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Kamal Mostafa - July 17, 2013, 10:46 p.m.
3.8.13.5 -stable review patch.  If anyone has any objections, please let me know.

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

From: Jan Kara <jack@suse.cz>

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

Patch

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index c0fbd96..1ec8761 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4523,7 +4523,7 @@  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);
@@ -4541,7 +4541,7 @@  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;
 }