Subject: Re: WARNING: refcount bug in sctp_wfree

From: Kees Cook <[email-masked]>
Date: Tue, 10 Mar 2020 09:01:18 -0700

On Tue, Mar 10, 2020 at 02:39:01AM -0700, syzbot wrote:
> syzbot has bisected this bug to:
> 
> commit fb041bb7c0a918b95c6889fc965cdc4a75b4c0ca
> Author: Will Deacon <[email-masked]>
> Date:   Thu Nov 21 11:59:00 2019 +0000
> 
>     locking/refcount: Consolidate implementations of refcount_t

I suspect this is just bisecting to here because it made the refcount
checks more strict?

-Kees

> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=117e9e91e00000
> start commit:   2c523b34 Linux 5.6-rc5
> git tree:       upstream
> final crash:    https://syzkaller.appspot.com/x/report.txt?x=137e9e91e00000
> console output: https://syzkaller.appspot.com/x/log.txt?x=157e9e91e00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=a5295e161cd85b82
> dashboard link: https://syzkaller.appspot.com/bug?extid=cea71eec5d6de256d54d
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=164b5181e00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=166dd70de00000
> 
> Reported-by: [email-masked]
> Fixes: fb041bb7c0a9 ("locking/refcount: Consolidate implementations of refcount_t")
> 
> For information about bisection process see: https://goo.gl/tpsmEJ#bisection

-- 
Kees Cook