Patchwork [4/4] ext4: Fix overflow when counting used blocks on 32-bit architectures

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Submitter Jan Kara
Date May 29, 2013, 12:05 p.m.
Message ID <1369829133-4307-5-git-send-email-jack@suse.cz>
Download mbox | patch
Permalink /patch/247258/
State Accepted
Headers show

Comments

Jan Kara - May 29, 2013, 12:05 p.m.
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>
---
 fs/ext4/inode.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
Theodore Ts'o - May 31, 2013, 11:42 p.m.
On Wed, May 29, 2013 at 02:05:33PM +0200, Jan Kara wrote:
> 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>

I've applied these four patches to the ext4 tree, thanks!!

     	     	   		       - Ted
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Patch

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index d6382b8..83d9e69 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4805,7 +4805,7 @@  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);
@@ -4823,7 +4823,7 @@  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;
 }