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

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Message-Id: <20180404184517.9f2b91b856a56f71464f5f7f@linux-foundation.org>
Date:   Wed, 4 Apr 2018 18:45:17 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        reiserfs-devel@...r.kernel.org,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Jeff Mahoney <jeffm@...e.com>, 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 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()?

--- 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;
_