linux-kernel - Re: [PATCH] ubifs: Fix a potential space leak problem while linking tmpfile

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Message-ID: <a3421498-e3a5-f7dc-50c6-15ef3cdfb51b@huawei.com>
Date:   Sat, 11 Jul 2020 14:44:53 +0800
From:   Zhihao Cheng <chengzhihao1@...wei.com>
To:     Richard Weinberger <richard@....at>
CC:     Richard Weinberger <richard.weinberger@...il.com>,
        linux-mtd <linux-mtd@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        yi zhang <yi.zhang@...wei.com>
Subject: Re: [PATCH] ubifs: Fix a potential space leak problem while linking
 tmpfile

在 2020/7/11 14:37, Zhihao Cheng 写道:
> 在 2020/7/7 20:47, Richard Weinberger 写道:
>> ----- Ursprüngliche Mail -----
>>>>> Perhaps I misunderstood what commit 32fe905c17f001 ("ubifs: Fix
>>>>> O_TMPFILE corner case in ubifs_link()") wanted to fix.
>>>>> I think orphan area is used to remind filesystem don't forget to 
>>>>> delete
>>>>> inodes (whose nlink is 0) in next unclean rebooting. Generally, 
>>>>> the file
>>>>> system is not corrupted caused by replaying orphan nodes.
>>>>> Ralph reported a filesystem corruption in combination with overlayfs.
>>>>> Can you tell me the details about that problem? Thanks.
>>>> On my test bed I didn't see a fs corruption, what I saw was a 
>>>> failing orphan
>>>> self test while playing with O_TMPFILE and linkat().
>>> Do we have a reproducer, or can I get the fail testcase? Is it a 
>>> xfstest
>>> case?
>> I think xfstests triggered it, yes.
>> Later today I can check. :)
>>
>> Thanks,
>> //richard
>>
>> .
>
> I think I have found the testcases, overlay/006 and overlay/041.
>
> The 'mv' and 'rm' operations will put lowertestfile into orphan list 
> twice, so we must reseve the orphan deletion operation in 
> ubifs_link(), otherwise the testcase fails and we will see the 
> following msg:
>
>   overlay/006 2s ... - output mismatch (see 
> /root/git/xfstests-dev/results//overlay/006.out.bad)
>     --- tests/overlay/006.out    2020-07-07 21:42:57.737000000 +0800
>     +++ /root/git/xfstests-dev/results//overlay/006.out.bad 2020-07-11 
> 14:31:55.340000000 +0800
>     @@ -1,2 +1,4 @@
>      QA output created by 006
>      Silence is golden
>     +rm: cannot remove 
> '/tmp/scratch/ovl-mnt/uppertestdir/lowertestfile': Invalid argument
>     +lowertestfile
>     ...
>
>   [  382.258210] UBIFS error (ubi0:1 pid 11896): orphan_add [ubifs]: 
> orphaned twice
>   [  382.352535] UBIFS error (ubi0:1 pid 11930): free_orphans [ubifs]: 
> orphan list not empty at unmount
>
>
> So, how about moving ubifs_delete_orphan() after ubifs_jnl_update() in 
> function ubifs_link(). Following modifications applied in linux-5.8 
> has been tested by overlay/041, overlay/006 and  other tmpfile cases 
> (generic/531, generic/530, generic/509, generic/389, generic/004).
>
Results for testcases generic/530, generic/509, generic/389 and 
generic/004 are still "not run".
> diff --git a/fs/ubifs/dir.c b/fs/ubifs/dir.c
> index ef85ec167a84..fd4443a5e8c6 100644
> --- a/fs/ubifs/dir.c
> +++ b/fs/ubifs/dir.c
> @@ -722,11 +722,6 @@ 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);
> -
> inc_nlink(inode);
> ihold(inode);
>         inode->i_ctime = current_time(inode);
> @@ -736,6 +731,11 @@ static int ubifs_link(struct dentry *old_dentry, 
> struct inode *dir,
>         err = ubifs_jnl_update(c, dir, &nm, inode, 0, 0);
>         if (err)
>                 goto out_cancel;
> +
> +       /* Handle O_TMPFILE corner case, it is allowed to link a 
> O_TMPFILE. */
> +       if (inode->i_nlink == 1)
> +               ubifs_delete_orphan(c, inode->i_ino);
> +
>         unlock_2_inodes(dir, inode);
>
>         ubifs_release_budget(c, &req);
> @@ -747,8 +747,6 @@ static int ubifs_link(struct dentry *old_dentry, 
> struct inode *dir,
>         dir->i_size -= sz_change;
>         dir_ui->ui_size = dir->i_size;
> drop_nlink(inode);
> -       if (inode->i_nlink == 0)
> -               ubifs_add_orphan(c, inode->i_ino);
>         unlock_2_inodes(dir, inode);
>         ubifs_release_budget(c, &req);
> iput(inode);
> -- 
>