From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Andrew Morton <akpm@linux-foundation.org>,
"James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>,
Helge Deller <deller@gmx.de>, Arnd Bergmann <arnd@arndb.de>,
Kees Cook <keescook@chromium.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-arch@vger.kernel.org, linux-ia64@vger.kernel.org,
linux-parisc@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org
Subject: [PATCH v4 11/13] lkdtm: Really write into kernel text in WRITE_KERN
Date: Tue, 15 Feb 2022 13:41:06 +0100 [thread overview]
Message-ID: <31e58eaffb5bc51c07d8d4891d1982100ade8cfc.1644928018.git.christophe.leroy@csgroup.eu> (raw)
In-Reply-To: <cover.1644928018.git.christophe.leroy@csgroup.eu>
WRITE_KERN is supposed to overwrite some kernel text, namely
do_overwritten() function.
But at the time being it overwrites do_overwritten() function
descriptor, not function text.
Fix it by dereferencing the function descriptor to obtain
function text pointer. Export dereference_function_descriptor()
for when LKDTM is built as a module.
And make do_overwritten() noinline so that it is really
do_overwritten() which is called by lkdtm_WRITE_KERN().
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
drivers/misc/lkdtm/perms.c | 8 +++++---
kernel/extable.c | 1 +
2 files changed, 6 insertions(+), 3 deletions(-)
diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
index 60b3b2fe929d..035fcca441f0 100644
--- a/drivers/misc/lkdtm/perms.c
+++ b/drivers/misc/lkdtm/perms.c
@@ -10,6 +10,7 @@
#include <linux/mman.h>
#include <linux/uaccess.h>
#include <asm/cacheflush.h>
+#include <asm/sections.h>
/* Whether or not to fill the target memory area with do_nothing(). */
#define CODE_WRITE true
@@ -37,7 +38,7 @@ static noinline void do_nothing(void)
}
/* Must immediately follow do_nothing for size calculuations to work out. */
-static void do_overwritten(void)
+static noinline void do_overwritten(void)
{
pr_info("do_overwritten wasn't overwritten!\n");
return;
@@ -113,8 +114,9 @@ void lkdtm_WRITE_KERN(void)
size_t size;
volatile unsigned char *ptr;
- size = (unsigned long)do_overwritten - (unsigned long)do_nothing;
- ptr = (unsigned char *)do_overwritten;
+ size = (unsigned long)dereference_function_descriptor(do_overwritten) -
+ (unsigned long)dereference_function_descriptor(do_nothing);
+ ptr = dereference_function_descriptor(do_overwritten);
pr_info("attempting bad %zu byte write at %px\n", size, ptr);
memcpy((void *)ptr, (unsigned char *)do_nothing, size);
diff --git a/kernel/extable.c b/kernel/extable.c
index 394c39b86e38..bda5e9761541 100644
--- a/kernel/extable.c
+++ b/kernel/extable.c
@@ -149,6 +149,7 @@ void *dereference_function_descriptor(void *ptr)
ptr = p;
return ptr;
}
+EXPORT_SYMBOL_GPL(dereference_function_descriptor);
void *dereference_kernel_function_descriptor(void *ptr)
{
--
2.34.1
next prev parent reply other threads:[~2022-02-15 12:42 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-15 12:40 [PATCH v4 00/13] Fix LKDTM for PPC64/IA64/PARISC v4 Christophe Leroy
2022-02-15 12:40 ` [PATCH v4 01/13] powerpc: Fix 'sparse' checking on PPC64le Christophe Leroy
2022-02-15 16:06 ` Kees Cook
2022-02-15 12:40 ` [PATCH v4 02/13] powerpc: Move and rename func_descr_t Christophe Leroy
2022-02-15 12:40 ` [PATCH v4 03/13] powerpc: Use 'struct func_desc' instead of 'struct ppc64_opd_entry' Christophe Leroy
2022-02-15 12:40 ` [PATCH v4 04/13] powerpc: Remove " Christophe Leroy
2022-02-15 12:41 ` [PATCH v4 05/13] powerpc: Prepare func_desc_t for refactorisation Christophe Leroy
2022-02-15 12:41 ` [PATCH v4 06/13] ia64: Rename 'ip' to 'addr' in 'struct fdesc' Christophe Leroy
2022-02-15 12:41 ` [PATCH v4 07/13] asm-generic: Define CONFIG_HAVE_FUNCTION_DESCRIPTORS Christophe Leroy
2022-02-15 12:41 ` [PATCH v4 08/13] asm-generic: Define 'func_desc_t' to commonly describe function descriptors Christophe Leroy
2022-02-15 12:41 ` [PATCH v4 09/13] asm-generic: Refactor dereference_[kernel]_function_descriptor() Christophe Leroy
2022-02-15 12:41 ` [PATCH v4 10/13] lkdtm: Force do_nothing() out of line Christophe Leroy
2022-02-15 12:41 ` Christophe Leroy [this message]
2022-02-15 12:41 ` [PATCH v4 12/13] lkdtm: Fix execute_[user]_location() Christophe Leroy
2022-02-15 12:41 ` [PATCH v4 13/13] lkdtm: Add a test for function descriptors protection Christophe Leroy
2022-02-15 16:07 ` [PATCH v4 00/13] Fix LKDTM for PPC64/IA64/PARISC v4 Kees Cook
2022-02-16 12:22 ` Michael Ellerman
2022-02-16 16:20 ` Kees Cook
2022-02-16 13:26 ` Helge Deller
2022-02-16 12:25 ` John Paul Adrian Glaubitz
2022-02-21 20:06 ` John Paul Adrian Glaubitz
2022-03-08 12:07 ` Michael Ellerman
2022-03-09 1:37 ` Michael Ellerman
2022-03-09 16:30 ` Kees Cook
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