From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Kees Cook <keescook@chromium.org>, Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Andrew Morton <akpm@linux-foundation.org>,
"James E.J. Bottomley" <James.Bottomley@hansenpartnership.com>,
Helge Deller <deller@gmx.de>, Arnd Bergmann <arnd@arndb.de>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
"linux-ia64@vger.kernel.org" <linux-ia64@vger.kernel.org>,
"linux-parisc@vger.kernel.org" <linux-parisc@vger.kernel.org>,
"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>
Subject: Re: [PATCH v3 08/12] asm-generic: Refactor dereference_[kernel]_function_descriptor()
Date: Mon, 14 Feb 2022 10:32:08 +0000 [thread overview]
Message-ID: <5bb6160d-0f7b-ad2b-8933-3cb97a535b54@csgroup.eu> (raw)
In-Reply-To: <202202101655.13C794F0F@keescook>
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@csgroup.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
next prev parent reply other threads:[~2022-02-14 11:04 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-17 12:38 [PATCH v3 00/12] Fix LKDTM for PPC64/IA64/PARISC Christophe Leroy
2021-10-17 12:38 ` [PATCH v3 01/12] powerpc: Move and rename func_descr_t Christophe Leroy
2021-10-18 5:58 ` Nicholas Piggin
2022-02-11 0:51 ` Kees Cook
2021-10-17 12:38 ` [PATCH v3 02/12] powerpc: Use 'struct func_desc' instead of 'struct ppc64_opd_entry' Christophe Leroy
2021-10-17 12:38 ` [PATCH v3 03/12] powerpc: Remove " Christophe Leroy
2021-10-17 12:38 ` [PATCH v3 04/12] powerpc: Prepare func_desc_t for refactorisation Christophe Leroy
2021-10-18 6:27 ` Nicholas Piggin
2021-10-18 7:08 ` Christophe Leroy
2022-02-11 0:54 ` Kees Cook
2022-02-11 7:39 ` Segher Boessenkool
2022-02-14 10:30 ` Christophe Leroy
2021-10-17 12:38 ` [PATCH v3 05/12] ia64: Rename 'ip' to 'addr' in 'struct fdesc' Christophe Leroy
2021-10-17 12:38 ` [PATCH v3 06/12] asm-generic: Define CONFIG_HAVE_FUNCTION_DESCRIPTORS Christophe Leroy
2021-10-17 12:38 ` [PATCH v3 07/12] asm-generic: Define 'func_desc_t' to commonly describe function descriptors Christophe Leroy
2021-10-18 6:29 ` Nicholas Piggin
2021-10-18 7:07 ` Christophe Leroy
2021-10-18 9:16 ` Nicholas Piggin
2021-10-17 12:38 ` [PATCH v3 08/12] asm-generic: Refactor dereference_[kernel]_function_descriptor() Christophe Leroy
2022-02-10 10:30 ` Michael Ellerman
2022-02-11 0:56 ` Kees Cook
2022-02-14 10:32 ` Christophe Leroy [this message]
2021-10-17 12:38 ` [PATCH v3 09/12] lkdtm: Force do_nothing() out of line Christophe Leroy
2021-10-17 12:38 ` [PATCH v3 10/12] lkdtm: Really write into kernel text in WRITE_KERN Christophe Leroy
2021-10-17 12:38 ` [PATCH v3 11/12] lkdtm: Fix execute_[user]_location() Christophe Leroy
2021-12-17 11:49 ` Christophe Leroy
2021-12-17 17:12 ` Helge Deller
2022-01-19 19:28 ` Christophe Leroy
2022-01-19 22:00 ` Kees Cook
2022-02-11 1:01 ` Kees Cook
2021-10-17 12:38 ` [PATCH v3 12/12] lkdtm: Add a test for function descriptors protection Christophe Leroy
2022-02-11 1:09 ` Kees Cook
2022-02-14 10:34 ` Christophe Leroy
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