linux-kernel - Re: [PATCH] Support resetting WARN

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Mon, 06 Nov 2017 11:18:09 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
        Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH] Support resetting WARN_ONCE for all architectures

Andrew Morton <akpm@...ux-foundation.org> writes:
> On Fri, 03 Nov 2017 20:38:03 +1100 Michael Ellerman <mpe@...erman.id.au> wrote:
>> Andi Kleen <andi@...stfloor.org> writes:
>> > diff --git a/lib/bug.c b/lib/bug.c
>> > index a6a1137d06db..7cb2d41845f7 100644
>> > --- a/lib/bug.c
>> > +++ b/lib/bug.c
>> > @@ -195,3 +195,24 @@ enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
>> >  
>> >  	return BUG_TRAP_TYPE_BUG;
>> >  }
>> > +
>> > +static void clear_once_table(struct bug_entry *start, struct bug_entry *end)
>> > +{
>> > +	struct bug_entry *bug;
>> > +
>> > +	for (bug = start; bug < end; bug++)
>> > +		bug->flags &= ~BUGFLAG_ONCE;
>> 
>> Clearing BUGFLAG_ONCE removes the once-ness permanently. ie. it becomes
>> a WARN().
>> 
>> You should be clearing BUGFLAG_DONE, which is the flag that says this
>> WARN has already triggered.
>
> This?

Yes.

> --- a/lib/bug.c~support-resetting-warn_once-for-all-architectures-v2-fix-fix-fix
> +++ a/lib/bug.c
> @@ -202,7 +202,7 @@ static void clear_once_table(struct bug_
>  	struct bug_entry *bug;
>  
>  	for (bug = start; bug < end; bug++)
> -		bug->flags &= ~BUGFLAG_ONCE;
> +		bug->flags &= ~BUGFLAG_DONE;
>  }
>  
>  void generic_bug_clear_once(void)
>
>
> And this is getting a bit nutty:
>
> support-resetting-warn_once.patch
> support-resetting-warn_once-checkpatch-fixes.patch
> support-resetting-warn_once-for-all-architectures.patch
> support-resetting-warn_once-for-all-architectures-v2.patch
> support-resetting-warn_once-for-all-architectures-v2-fix.patch
> support-resetting-warn_once-for-all-architectures-v2-fix-fix.patch
> support-resetting-warn_once-for-all-architectures-v2-fix-fix-fix.patch

Quite. They should probably all just be squashed together.

> I'll push all this at Stephen later today.  Someone please tell me
> whether this code actually works!

I've tested Andi's two patches with the above one-liner and that worked
for me. I'll test again on linux-next once it's in there to confirm.

cheers