2016-08-22 05:50:46

by Daeho Jeong

Subject: [PATCH RESEND] ext4: reinforce check of i_dtime when clearing high fields of uid and gid

Now, ext4_do_update_inode() clears high 16-bit fields of uid/gid
of deleted and evicted inode to fix up interoperability with old
kernels. However, it checks only i_dtime of an inode to determine
whether the inode was deleted and evicted, and this is very risky,
because i_dtime can be used for the pointer maintaining orphan inode
list, too. We need to further check whether the i_dtime is being
used for the orphan inode list even if the i_dtime is not NULL.

We found that high 16-bit fields of uid/gid of inode are unintentionally
and permanently cleared when the inode truncation is just triggered,
but not finished, and the inode metadata, whose high uid/gid bits are
cleared, is written on disk, and the sudden power-off follows that
in order.

Signed-off-by: Daeho Jeong <[email protected]>
Signed-off-by: Hobin Woo <[email protected]>
---
fs/ext4/inode.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index f7140ca..bb5aede 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4785,14 +4785,14 @@ static int ext4_do_update_inode(handle_t *handle,
* Fix up interoperability with old kernels. Otherwise, old inodes get
* re-used with the upper 16 bits of the uid/gid intact
*/
- if (!ei->i_dtime) {
+ if (ei->i_dtime && list_empty(&ei->i_orphan)) {
+ raw_inode->i_uid_high = 0;
+ raw_inode->i_gid_high = 0;
+ } else {
raw_inode->i_uid_high =
cpu_to_le16(high_16_bits(i_uid));
raw_inode->i_gid_high =
cpu_to_le16(high_16_bits(i_gid));
- } else {
- raw_inode->i_uid_high = 0;
- raw_inode->i_gid_high = 0;
}
} else {
raw_inode->i_uid_low = cpu_to_le16(fs_high2lowuid(i_uid));
--
1.7.9.5

2016-09-06 03:02:10

by Theodore Ts'o

Subject: Re: [PATCH RESEND] ext4: reinforce check of i_dtime when clearing high fields of uid and gid

On Mon, Aug 22, 2016 at 02:51:25PM +0900, Daeho Jeong wrote:
> Now, ext4_do_update_inode() clears high 16-bit fields of uid/gid
> of deleted and evicted inode to fix up interoperability with old
> kernels. However, it checks only i_dtime of an inode to determine
> whether the inode was deleted and evicted, and this is very risky,
> because i_dtime can be used for the pointer maintaining orphan inode
> list, too. We need to further check whether the i_dtime is being
> used for the orphan inode list even if the i_dtime is not NULL.
>
> We found that high 16-bit fields of uid/gid of inode are unintentionally
> and permanently cleared when the inode truncation is just triggered,
> but not finished, and the inode metadata, whose high uid/gid bits are
> cleared, is written on disk, and the sudden power-off follows that
> in order.
>
> Signed-off-by: Daeho Jeong <[email protected]>
> Signed-off-by: Hobin Woo <[email protected]>

Thanks, applied.

- Ted