linux-kernel - Re: [PATCH?] reiserfs: prevent panic: don't allow %-char in journal dev. name

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Date:   Wed, 4 Apr 2018 19:05:31 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Jeff Mahoney <jeffm@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        reiserfs-devel@...r.kernel.org,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Jan Kara <jack@...e.com>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Artem Bityutskiy <dedekind1@...il.com>,
        syzkaller-bugs@...glegroups.com,
        syzbot+6bd77b88c1977c03f584@...kaller.appspotmail.com
Subject: Re: [PATCH?] reiserfs: prevent panic: don't allow %-char in journal
 dev. name

On 04/04/2018 06:48 PM, Jeff Mahoney wrote:
> On 4/4/18 9:45 PM, Andrew Morton wrote:
>> On Wed, 4 Apr 2018 18:25:16 -0700 Randy Dunlap <rdunlap@...radead.org> wrote:
>>
>>> From: Randy Dunlap <rdunlap@...radead.org>
>>>
>>> If the reiserfs mount option's journal name contains a '%' character,
>>> it can lead to a WARN_ONCE() in lib/vsprintf.c::format_decode(),
>>> saying: "Please remove unsupported %/ in format string."
>>> That's OK until panic_on_warn is set, at which point it's dead, Jim.
>>>
>>> To placate this situation, check the journal name string for a '%'
>>> character and return an error if one is found. Also print a warning
>>> (one that won't panic the kernel) about the invalid journal name (e.g.):
>>>
>>>   reiserfs: journal device name is invalid: %/file0
>>>
>>> (In this example, the caller app specified the journal device name as
>>> "%/file0".)
>>>
>>
>> Well, that is a valid filename and we should support it...
>>
>> Isn't the bug in journal_init_dev()?

OK, thanks.

> Yep.  That's exactly it.
> 
> Acked-by: Jeff Mahoney <jeffm@...e.com>
> 
> Thanks,
> 
> -Jeff
> 
>> --- a/fs/reiserfs/journal.c~a
>> +++ a/fs/reiserfs/journal.c
>> @@ -2643,7 +2643,7 @@ static int journal_init_dev(struct super
>>  	if (IS_ERR(journal->j_dev_bd)) {
>>  		result = PTR_ERR(journal->j_dev_bd);
>>  		journal->j_dev_bd = NULL;
>> -		reiserfs_warning(super,
>> +		reiserfs_warning(super, "sh-457",
>>  				 "journal_init_dev: Cannot open '%s': %i",
>>  				 jdev_name, result);
>>  		return result;
>> _
>>
>>
> 
> 


-- 
~Randy