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Date: Sat, 20 Feb 2016 20:50:45 +0000
From: Al Viro <viro@ZenIV.linux.org.uk>
To: =?iso-8859-1?Q?Micka=EBl_Sala=FCn?= <mic@digikod.net>
Cc: Dmitry Vyukov <dvyukov@google.com>,
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Subject: Re: fs: NULL deref in atime_needs_update
Message-ID: <20160220205044.GJ17997@ZenIV.linux.org.uk>
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 <56C3B35E.6020109@digikod.net>
 <CACT4Y+YOnDbgo2tEp8BxPy20awzcJ7x0Vw=phDGQ3sUMaE7RvA@mail.gmail.com>
 <20160220032127.GA19926@ZenIV.linux.org.uk>
 <20160220035442.GE17997@ZenIV.linux.org.uk>
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On Sat, Feb 20, 2016 at 09:26:28PM +0100, Micka�l Sala�n wrote:
> > +	if (unlikely(error > 0)) {
> > +		WARN_ON(1);
> > +		error = -EINVAL;
> > +	}
> >  	if (got_write)
> >  		mnt_drop_write(nd->path.mnt);
> >  	path_put(&save_parent);
> > 
> 
> I think your warning patch should be upstreamed to detect such cases :)

I'm not sure whether it's better done there or one step closer to the
source - e.g. telling whether it was bogus ->open() or a bogus LSM hook
(and _which_ bogus LSM hook had it been) would be hard with that location
of test.

It still leaves the question of what's going on in Dmitry's tests - it might
be one of those source or it might be something else entirely; this location
of test would at least tell whether a stack underrun is involved or not...

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Date: Sat, 20 Feb 2016 20:50:45 +0000
From: Al Viro <viro@ZenIV.linux.org.uk>
To: =?iso-8859-1?Q?Micka=EBl_Sala=FCn?= <mic@digikod.net>
Cc: Dmitry Vyukov <dvyukov@google.com>,
        "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        syzkaller <syzkaller@googlegroups.com>,
        Kostya Serebryany <kcc@google.com>,
        Alexander Potapenko <glider@google.com>,
        Sasha Levin <sasha.levin@oracle.com>
Subject: Re: fs: NULL deref in atime_needs_update
Message-ID: <20160220205044.GJ17997@ZenIV.linux.org.uk>
References: <CACT4Y+ae=DQjrTtwSqm1PJ9rsnRAvKiBkRjBqaQH6f6W1dOh2Q@mail.gmail.com>
 <56C3B35E.6020109@digikod.net>
 <CACT4Y+YOnDbgo2tEp8BxPy20awzcJ7x0Vw=phDGQ3sUMaE7RvA@mail.gmail.com>
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On Sat, Feb 20, 2016 at 09:26:28PM +0100, Mickaël Salaün wrote:
> > +	if (unlikely(error > 0)) {
> > +		WARN_ON(1);
> > +		error = -EINVAL;
> > +	}
> >  	if (got_write)
> >  		mnt_drop_write(nd->path.mnt);
> >  	path_put(&save_parent);
> > 
> 
> I think your warning patch should be upstreamed to detect such cases :)

I'm not sure whether it's better done there or one step closer to the
source - e.g. telling whether it was bogus ->open() or a bogus LSM hook
(and _which_ bogus LSM hook had it been) would be hard with that location
of test.

It still leaves the question of what's going on in Dmitry's tests - it might
be one of those source or it might be something else entirely; this location
of test would at least tell whether a stack underrun is involved or not...