linux-kernel - Re: [PATCH] ubifs: Fix O_TMPFILE corner case in ubifs

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Message-ID: <646ae733-5037-3072-7151-b055a8fa1521@intel.com>
Date:   Thu, 30 Mar 2017 14:57:40 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Richard Weinberger <richard@....at>, linux-mtd@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, dedekind1@...il.com,
        stable@...r.kernel.org,
        Ralph Sennhauser <ralph.sennhauser@...il.com>,
        Amir Goldstein <amir73il@...il.com>
Subject: Re: [PATCH] ubifs: Fix O_TMPFILE corner case in ubifs_link()

On 30/03/17 13:23, Richard Weinberger 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.

Deleting the orphan looks right.  Just need to understand whether the
recovery would do the right thing - actually it looks like O_TMPFILE might
be OK and in other case we might be failing to remove nodes with sequence
numbers greater than the deletion inode.