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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.

Cc: stable@vger.kernel.org
Signed-off-by: Daeho Jeong <daeho.jeong@samsung.com>
Signed-off-by: Hobin Woo <hobin.woo@samsung.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Daeho Jeong 2016-09-05 22:56:10 -04:00 committed by Theodore Ts'o
parent 8913f343cd
commit 93e3b4e663
1 changed files with 4 additions and 4 deletions
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8
fs/ext4/inode.c
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@ -4814,14 +4814,14 @@ 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));