linux-kernel - Re: [PATCH] ovl: Prevent rw remount when it should be ro mount

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Message-ID: <54A6D40E.705@gmail.com>
Date:	Sat, 03 Jan 2015 02:23:26 +0900
From:	Seunghun Lee <waydi1@...il.com>
To:	sedat.dilek@...il.com
CC:	Miklos Szeredi <miklos@...redi.hu>,
	Richard Weinberger <richard.weinberger@...il.com>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ovl: Prevent rw remount when it should be ro mount


On 01/02/2015 03:33 AM, Sedat Dilek wrote:
> On Thu, Jan 1, 2015 at 4:38 PM, Seunghun Lee <waydi1@...il.com> wrote:
>> Overlayfs should be mounted read-only when upper fs is r/o or nonexistend.
>> But now it can be remounted read-write and this can causes kernel panic.
>> So we should prevent read-write remount when the above situation.
>>
> Cannot say much to the code, but you have some typos in your commit-message.
> Here some corrections... wording, style etc.
>
> ...when upper-fs (with a dash) is read-only (if you write read-write
> below) or nonexisten*t*...
> ...this can cause (without s at the end)...
> ...when the above situation *happens* (missing word)...
>
> - Sedat -
>
>> Signed-off-by: Seunghun Lee <waydi1@...il.com>
>> ---
>>  fs/overlayfs/super.c | 11 +++++++++++
>>  1 file changed, 11 insertions(+)
>>
>> diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
>> index 84f3144..8944651 100644
>> --- a/fs/overlayfs/super.c
>> +++ b/fs/overlayfs/super.c
>> @@ -522,10 +522,21 @@ static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
>>         return 0;
>>  }
>>
>> +static int ovl_remount(struct super_block *sb, int *flags, char *data)
>> +{
>> +       struct ovl_fs *ufs = sb->s_fs_info;
>> +
>> +       if (!ufs->upper_mnt || (ufs->upper_mnt->mnt_sb->s_flags & MS_RDONLY))
>> +               *flags |= MS_RDONLY;
>> +
>> +       return 0;
>> +}
>> +
>>  static const struct super_operations ovl_super_operations = {
>>         .put_super      = ovl_put_super,
>>         .statfs         = ovl_statfs,
>>         .show_options   = ovl_show_options,
>> +       .remount_fs     = ovl_remount,
>>  };
>>
>>  enum {
>> --
>> 2.1.3
>>
Thank you for your correction!

I will fix it.

Thanks.
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