linux-kernel - Re: lockdep warning while booting POWER9 PowerNV

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]

Message-ID: <87v9r8g3oe.fsf@dja-thinkpad.axtens.net>
Date:   Mon, 25 Nov 2019 12:12:01 +1100
From:   Daniel Axtens <dja@...ens.net>
To:     Michael Ellerman <mpe@...erman.id.au>,
        Bart Van Assche <bvanassche@....org>, Qian Cai <cai@....pw>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org
Subject: Re: lockdep warning while booting POWER9 PowerNV

Hi Michael,

>>> Once in a while, booting an IBM POWER9 PowerNV system (8335-GTH) would generate
>>> a warning in lockdep_register_key() at,
>>> 
>>> if (WARN_ON_ONCE(static_obj(key)))
>>> 
>>> because
>>> 
>>> key = 0xc0000000019ad118
>>> &_stext = 0xc000000000000000
>>> &_end = 0xc0000000049d0000
>>> 
>>> i.e., it will cause static_obj() returns 1.
>>
>> (back from a trip)
>>
>> Hi Qian,
>>
>> Does this mean that on POWER9 it can happen that a dynamically allocated 
>> object has an address that falls between &_stext and &_end?
>
> I thought that was true on all arches due to initmem, but seems not.
>
> I guess we have the same problem as s390 and we need to define
> arch_is_kernel_initmem_freed().
>
> Qian, can you try this:
>
> diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
> index 4a1664a8658d..616b1b7b7e52 100644
> --- a/arch/powerpc/include/asm/sections.h
> +++ b/arch/powerpc/include/asm/sections.h
> @@ -5,8 +5,22 @@
>  
>  #include <linux/elf.h>
>  #include <linux/uaccess.h>
> +
> +#define arch_is_kernel_initmem_freed arch_is_kernel_initmem_freed
> +
>  #include <asm-generic/sections.h>
>  
> +extern bool init_mem_is_free;
> +
> +static inline int arch_is_kernel_initmem_freed(unsigned long addr)
> +{
> +	if (!init_mem_is_free)
> +		return 0;
> +
> +	return addr >= (unsigned long)__init_begin &&
> +		addr < (unsigned long)__init_end;
> +}
> +
>  extern char __head_end[];
>  
>  #ifdef __powerpc64__
>

This also fixes the following syzkaller bug:
https://syzkaller-ppc64.appspot.com/bug?id=cfdf75cd985012d0124cd41e6fa095d33e7d0f6b
https://github.com/linuxppc/issues/issues/284

Would you like me to do up a nice commit message for it?

Regards,
Daniel

>
> cheers