linux-kernel - Re: KASAN: use-after-free Read in locks_delete

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Date:   Tue, 20 Nov 2018 07:57:23 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Bruce Fields <bfields@...ldses.org>
Cc:     Jeff Layton <jlayton@...nel.org>, NeilBrown <neilb@...e.com>,
        syzbot <syzbot+a4a3d526b4157113ec6a@...kaller.appspotmail.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        syzkaller-bugs@...glegroups.com, Al Viro <viro@...iv.linux.org.uk>
Subject: Re: KASAN: use-after-free Read in locks_delete_block

On Sat, Nov 17, 2018 at 3:03 PM, Bruce Fields <bfields@...ldses.org> wrote:
> On Sat, Nov 17, 2018 at 08:33:27AM -0500, Jeff Layton wrote:
>> Thanks for the explanation, Dmitry. I've added the tag to the patch in
>> my tree. It should show up in linux-next soon.
>>
>> I still find it a little misleading to say that syzbot reported a bug
>> when it actually found a bug inside an earlier version of the patch, but
>> I'll just learn to get over it.
>
> The usual tag for someone that found a bug in an earlier version of a
> patch would be Reviewed-by:.  Is there any reason we can't use that
> here?  The "syzbot+..." email should be enough on its own, I can't see a
> reason why their scripts would need to require a particular tag.  Or
> maybe we could use Tested-by:, or some other tag made up for this case?
>
> I do worry that someone who sees "Reported-by:..." might for example
> mistakenly assume that it would help to backport that patch if they see
> a similar-looking oops.

I see. It may also be picked by scripts that detects patches that need
to be backported to stable because of the "Reported-by: syzbot" tag.
This is somewhat unfortunate.

There is no problem parsing another tag on syzbot side. Does Tested-by
look good to you? If it found a bug in the patch and then it was
fixed, Tested-by looks reasonable. And we also detect
Reported-and-tested-by already because that's what syzbot suggests
after it tested a proposed fix for a bug.

I am somewhat concerned how to spread this information across all
kernel developers. There is effectively no way to do this. We can't
expect people to read docs, they generally don't. I guess I just
document this at "See https://goo.gl/tpsmEJ for more information" and
then we can point other people there if/when this concern pops up
again.