[PATCH] ubifs: Fix O_TMPFILE corner case in ubifs_link()

[Amir Goldstein]

On Thu, Mar 30, 2017 at 1:23 PM, Richard Weinberger <richard at nod.at> wrote:
> Am 30.03.2017 um 11:49 schrieb Richard Weinberger:
>> Am 30.03.2017 um 11:32 schrieb Adrian Hunter:
>>>> diff --git a/fs/ubifs/dir.c b/fs/ubifs/dir.c
>>>> index 0858213a4e63..0139155045fe 100644
>>>> --- a/fs/ubifs/dir.c
>>>> +++ b/fs/ubifs/dir.c
>>>> @@ -748,6 +748,11 @@ static int ubifs_link(struct dentry *old_dentry, struct inode *dir,
>>>>             goto out_fname;
>>>>
>>>>     lock_2_inodes(dir, inode);
>>>> +
>>>> +   /* Handle O_TMPFILE corner case, it is allowed to link a O_TMPFILE. */
>>>> +   if (inode->i_nlink == 0)
>>>> +           ubifs_delete_orphan(c, inode->i_ino);
>>>
>>> Isn't there also a deletion inode in the journal?  If the recovery sees that
>>> won't it delete the file data?
>>
>> Yes, but ubifs_link() adds a new journal entry which revives the inode.
>> This should cancel out the deletion, right?
>> You know the UBIFS journal better than I do. :-)
>
> Reading deeper into the proved that I was wrong.
> AFAIKT UBIFS' journal has currently no way to revive a deleted inode.
> So, we have to think about a new solution.
>

Not that I know anything about ubifs, but why do you need the deleted
inode record in the first place for an O_TMPFILE.
vfs ensures you that you can only link back an O_TMPFILE, not a deleted
inode.

It does not appear to be the right thing to do to pass deletion=1 to
ubifs_jnl_update(), but deletion=0 doesn't look right as well..