linux-kernel - Re: [PATCH v3 08/12] asm-generic: Refactor dereference_[kernel]_function

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: <5bb6160d-0f7b-ad2b-8933-3cb97a535b54@csgroup.eu>
Date:   Mon, 14 Feb 2022 10:32:08 +0000
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Kees Cook <keescook@...omium.org>,
        Michael Ellerman <mpe@...erman.id.au>
CC:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "James E.J. Bottomley" <James.Bottomley@...senpartnership.com>,
        Helge Deller <deller@....de>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-ia64@...r.kernel.org" <linux-ia64@...r.kernel.org>,
        "linux-parisc@...r.kernel.org" <linux-parisc@...r.kernel.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH v3 08/12] asm-generic: Refactor
 dereference_[kernel]_function_descriptor()



Le 11/02/2022 à 01:56, Kees Cook a écrit :
> On Thu, Feb 10, 2022 at 09:30:43PM +1100, Michael Ellerman wrote:
>> Christophe Leroy <christophe.leroy@...roup.eu> writes:
>>> diff --git a/kernel/extable.c b/kernel/extable.c
>>> index b0ea5eb0c3b4..1ef13789bea9 100644
>>> --- a/kernel/extable.c
>>> +++ b/kernel/extable.c
>>> @@ -159,12 +160,32 @@ int kernel_text_address(unsigned long addr)
>>>   }
>>>   
>>>   /*
>>> - * On some architectures (PPC64, IA64) function pointers
>>> + * On some architectures (PPC64, IA64, PARISC) function pointers
>>>    * are actually only tokens to some data that then holds the
>>>    * real function address. As a result, to find if a function
>>>    * pointer is part of the kernel text, we need to do some
>>>    * special dereferencing first.
>>>    */
>>> +#ifdef CONFIG_HAVE_FUNCTION_DESCRIPTORS
>>> +void *dereference_function_descriptor(void *ptr)
>>> +{
>>> +	func_desc_t *desc = ptr;
>>> +	void *p;
>>> +
>>> +	if (!get_kernel_nofault(p, (void *)&desc->addr))
>>> +		ptr = p;
>>> +	return ptr;
>>> +}
>>
>> This needs an EXPORT_SYMBOL_GPL(), otherwise the build breaks after
>> patch 10 with CONFIG_LKDTM=m.
> 
> Oh good catch!
> 
> (There have been a few cases of LKDTM=m being the only thing needed a
> symbol, so I've pondered giving it a namespace or constructing a little
> ifdef wrapper... but this seems ok to export...)
> 

powerpc and ia64 had it as a static inline, but parisc had it as a plain 
function and didn't export it. So I guess the export is not required at 
this point. I will export it in patch 10 when it becomes necessary.

Christophe