linux-kernel - Re: tip -ENOBOOT - bisected to locking/refcounts, x86/asm: Implement fast refcount overflow protection

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Date:   Tue, 29 Aug 2017 11:41:20 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Mike Galbraith <efault@....de>
Cc:     LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
        "Reshetova, Elena" <elena.reshetova@...el.com>
Subject: Re: tip -ENOBOOT - bisected to locking/refcounts, x86/asm: Implement
 fast refcount overflow protection

On Tue, Aug 29, 2017 at 11:10 AM, Mike Galbraith <efault@....de> wrote:
> On Tue, 2017-08-29 at 18:55 +0200, Mike Galbraith wrote:
>> On Tue, 2017-08-29 at 08:58 -0700, Kees Cook wrote:
>> >
>> > Ah-ha, found the tip-bot commit now that disables the x86 refcount
>> > implementation. Can you boot with CONFIG_REFCOUNT_FULL=y?
>>
>> Will do in the A.M.
>
> (It's A.M. somewhere..)  That boots fine.

Okay, thanks! I think we've seen this before, but couldn't reproduce
it. The issue is:

static void netlink_sock_destruct(struct sock *sk)
{
...
        WARN_ON(refcount_read(&sk->sk_wmem_alloc));
...
}

Can you also test with 14afee4b6092 ("net: convert sock.sk_wmem_alloc
from atomic_t to refcount_t") reverted (instead of ARCH_HAS_REFCOUNT
disabled)?

I'll try again to reproduce this...

Thanks!

-Kees

-- 
Kees Cook
Pixel Security