linux-kernel - Re: kernel BUG at fs/inode.c:LINE!

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Date:   Wed, 19 Dec 2018 08:05:35 +0800
From:   Ian Kent <raven@...maw.net>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Al Viro <viro@...iv.linux.org.uk>,
        syzbot <syzbot+5399ed0832693e29f392@...kaller.appspotmail.com>,
        DmitryVyukov <dvyukov@...gle.com>, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: kernel BUG at fs/inode.c:LINE!

On Tue, 2018-12-18 at 13:09 -0800, Andrew Morton wrote:
> On Tue, 18 Dec 2018 19:34:57 +0800 Ian Kent <raven@...maw.net> wrote:
> 
> > > See 
> > > 
https://www.ozlabs.org/~akpm/mmotm/broken-out/autofs-fix-possible-inode-leak-in-autofs_fill_super.patch
> > > 
> > > I think this will fix it, I'll forward it to Andrew if you agree:
> > 
> > Actually, looking at it again the above patch is plain not needed,
> > dropping it and updating the patch which follows it in the series
> > is what needs to be done.
> > 
> > Andrew, what should I do to make this easiest for you to handle,
> > a respost with v2 in the subject of the patch affected by dropping
> > the above patch?
> 
> I dropped the patch and fixed up the fallout.

Thanks Andrew, much appreciated.

> 
> The patch wasn't true anyway.  "There is no check at all for a failure
> to allocate the root inode in autofs_fill_super(), handle it." In fact,
> d_make_root(NULL) will just return NULL and autofs_fill_super() handles
> that appropriately.

The not so funny thing is that I'm sure I looked at this some time
in the distant past and saw how d_make_root() behaved.

The lesson for me is don't try and fix other things seen while working
on something else, return later and do it properly.

> 
> However let's note that when autofs_get_inode() or d_make_root() fail,
> autofs_fill_super() will return -EINVAL.  Should have been -ENOMEM, I
> guess?
> 

That's right, but I don't think that's urgent so I'll send a patch for
it after the coming merge window.

The strictexpire option addition is urgent for me so I don't want to
upset any chance of that being merged sooner rather than later.

Ian