From: Kees Cook <keescook@chromium.org>
To: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: linux-arch@vger.kernel.org, linux-ia64@vger.kernel.org,
linux-parisc@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Helge Deller <deller@gmx.de>,
linux-kernel@vger.kernel.org,
"James E.J. Bottomley" <James.Bottomley@hansenpartnership.com>,
linux-mm@kvack.org, Paul Mackerras <paulus@samba.org>,
Andrew Morton <akpm@linux-foundation.org>,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v2 11/13] lkdtm: Fix lkdtm_EXEC_RODATA()
Date: Fri, 15 Oct 2021 14:32:58 -0700 [thread overview]
Message-ID: <202110151432.D8203C19@keescook> (raw)
In-Reply-To: <44946ed0340013a52f8acdee7d6d0781f145cd6b.1634190022.git.christophe.leroy@csgroup.eu>
On Thu, Oct 14, 2021 at 07:50:00AM +0200, Christophe Leroy wrote:
> Behind its location, lkdtm_EXEC_RODATA() executes
> lkdtm_rodata_do_nothing() which is a real function,
> not a copy of do_nothing().
>
> So executes it directly instead of using execute_location().
>
> This is necessary because following patch will fix execute_location()
> to use a copy of the function descriptor of do_nothing() and
> function descriptor of lkdtm_rodata_do_nothing() might be different.
>
> And fix displayed addresses by dereferencing the function descriptors.
>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
I still don't understand this -- it doesn't look needed at all given the
changes in patch 12. (i.e. everything is using
dereference_function_descriptor() now)
Can't this patch be dropped?
-Kees
> ---
> drivers/misc/lkdtm/perms.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
> index 035fcca441f0..5266dc28df6e 100644
> --- a/drivers/misc/lkdtm/perms.c
> +++ b/drivers/misc/lkdtm/perms.c
> @@ -153,7 +153,14 @@ void lkdtm_EXEC_VMALLOC(void)
>
> void lkdtm_EXEC_RODATA(void)
> {
> - execute_location(lkdtm_rodata_do_nothing, CODE_AS_IS);
> + pr_info("attempting ok execution at %px\n",
> + dereference_function_descriptor(do_nothing));
> + do_nothing();
> +
> + pr_info("attempting bad execution at %px\n",
> + dereference_function_descriptor(lkdtm_rodata_do_nothing));
> + lkdtm_rodata_do_nothing();
> + pr_err("FAIL: func returned\n");
> }
>
> void lkdtm_EXEC_USERSPACE(void)
> --
> 2.31.1
>
--
Kees Cook
next prev parent reply other threads:[~2021-10-15 21:33 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-14 5:49 [PATCH v2 00/13] Fix LKDTM for PPC64/IA64/PARISC Christophe Leroy
2021-10-14 5:49 ` [PATCH v2 01/13] powerpc: Move 'struct ppc64_opd_entry' back into asm/elf.h Christophe Leroy
2021-10-14 21:26 ` Daniel Axtens
2021-10-15 5:57 ` Nicholas Piggin
2021-10-14 5:49 ` [PATCH v2 02/13] powerpc: Rename 'funcaddr' to 'addr' in 'struct ppc64_opd_entry' Christophe Leroy
2021-10-14 21:45 ` Daniel Axtens
2021-10-15 4:59 ` Christophe Leroy
2021-10-15 6:01 ` Nicholas Piggin
2021-10-14 5:49 ` [PATCH v2 03/13] powerpc: Remove func_descr_t Christophe Leroy
2021-10-14 22:17 ` Daniel Axtens
2021-10-15 5:19 ` Christophe Leroy
2021-10-15 6:11 ` Nicholas Piggin
2021-10-14 5:49 ` [PATCH v2 04/13] powerpc: Prepare func_desc_t for refactorisation Christophe Leroy
2021-10-14 5:49 ` [PATCH v2 05/13] ia64: Rename 'ip' to 'addr' in 'struct fdesc' Christophe Leroy
2021-10-14 5:49 ` [PATCH v2 06/13] asm-generic: Use HAVE_FUNCTION_DESCRIPTORS to define associated stubs Christophe Leroy
2021-10-15 6:16 ` Nicholas Piggin
2021-10-15 6:24 ` Christophe Leroy
2021-10-15 8:02 ` Nicholas Piggin
2021-10-15 11:52 ` Nicholas Piggin
2021-10-14 5:49 ` [PATCH v2 07/13] asm-generic: Define 'func_desc_t' to commonly describe function descriptors Christophe Leroy
2021-10-14 6:52 ` Arnd Bergmann
2021-10-14 5:49 ` [PATCH v2 08/13] asm-generic: Refactor dereference_[kernel]_function_descriptor() Christophe Leroy
2021-10-15 7:00 ` Nicholas Piggin
2021-10-14 5:49 ` [PATCH v2 09/13] lkdtm: Force do_nothing() out of line Christophe Leroy
2021-10-14 5:49 ` [PATCH v2 10/13] lkdtm: Really write into kernel text in WRITE_KERN Christophe Leroy
2021-10-14 5:50 ` [PATCH v2 11/13] lkdtm: Fix lkdtm_EXEC_RODATA() Christophe Leroy
2021-10-15 21:32 ` Kees Cook [this message]
2021-10-16 6:41 ` Christophe Leroy
2021-10-17 7:50 ` Christophe Leroy
2021-10-14 5:50 ` [PATCH v2 12/13] lkdtm: Fix execute_[user]_location() Christophe Leroy
2021-10-15 21:31 ` Kees Cook
2021-10-16 6:42 ` Christophe Leroy
2021-11-16 15:07 ` Christophe Leroy
2021-10-14 5:50 ` [PATCH v2 13/13] lkdtm: Add a test for function descriptors protection Christophe Leroy
2021-10-15 21:35 ` Kees Cook
2021-10-16 6:28 ` Christophe Leroy
2021-10-14 21:35 ` [PATCH v2 00/13] Fix LKDTM for PPC64/IA64/PARISC Daniel Axtens
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