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 13/13] lkdtm: Add a test for function descriptors protection
Date: Tue, 15 Feb 2022 13:41:08 +0100 [thread overview]
Message-ID: <7eeba50d16a35e9d799820e43304150225f20197.1644928018.git.christophe.leroy@csgroup.eu> (raw)
In-Reply-To: <cover.1644928018.git.christophe.leroy@csgroup.eu>
Add WRITE_OPD to check that you can't modify function
descriptors.
Gives the following result when function descriptors are
not protected:
lkdtm: Performing direct entry WRITE_OPD
lkdtm: attempting bad 16 bytes write at c00000000269b358
lkdtm: FAIL: survived bad write
lkdtm: do_nothing was hijacked!
Looks like a standard compiler barrier() is not enough to force
GCC to use the modified function descriptor. Had to add a fake empty
inline assembly to force GCC to reload the function descriptor.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Acked-by: Kees Cook <keescook@chromium.org>
---
drivers/misc/lkdtm/core.c | 1 +
drivers/misc/lkdtm/lkdtm.h | 1 +
drivers/misc/lkdtm/perms.c | 22 ++++++++++++++++++++++
tools/testing/selftests/lkdtm/tests.txt | 1 +
4 files changed, 25 insertions(+)
diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c
index f69b964b9952..e2228b6fc09b 100644
--- a/drivers/misc/lkdtm/core.c
+++ b/drivers/misc/lkdtm/core.c
@@ -149,6 +149,7 @@ static const struct crashtype crashtypes[] = {
CRASHTYPE(WRITE_RO),
CRASHTYPE(WRITE_RO_AFTER_INIT),
CRASHTYPE(WRITE_KERN),
+ CRASHTYPE(WRITE_OPD),
CRASHTYPE(REFCOUNT_INC_OVERFLOW),
CRASHTYPE(REFCOUNT_ADD_OVERFLOW),
CRASHTYPE(REFCOUNT_INC_NOT_ZERO_OVERFLOW),
diff --git a/drivers/misc/lkdtm/lkdtm.h b/drivers/misc/lkdtm/lkdtm.h
index d6137c70ebbe..305fc2ec3f25 100644
--- a/drivers/misc/lkdtm/lkdtm.h
+++ b/drivers/misc/lkdtm/lkdtm.h
@@ -106,6 +106,7 @@ void __init lkdtm_perms_init(void);
void lkdtm_WRITE_RO(void);
void lkdtm_WRITE_RO_AFTER_INIT(void);
void lkdtm_WRITE_KERN(void);
+void lkdtm_WRITE_OPD(void);
void lkdtm_EXEC_DATA(void);
void lkdtm_EXEC_STACK(void);
void lkdtm_EXEC_KMALLOC(void);
diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
index 1cf24c4a79e9..2c6aba3ff32b 100644
--- a/drivers/misc/lkdtm/perms.c
+++ b/drivers/misc/lkdtm/perms.c
@@ -44,6 +44,11 @@ static noinline void do_overwritten(void)
return;
}
+static noinline void do_almost_nothing(void)
+{
+ pr_info("do_nothing was hijacked!\n");
+}
+
static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
{
if (!have_function_descriptors())
@@ -144,6 +149,23 @@ void lkdtm_WRITE_KERN(void)
do_overwritten();
}
+void lkdtm_WRITE_OPD(void)
+{
+ size_t size = sizeof(func_desc_t);
+ void (*func)(void) = do_nothing;
+
+ if (!have_function_descriptors()) {
+ pr_info("XFAIL: Platform doesn't use function descriptors.\n");
+ return;
+ }
+ pr_info("attempting bad %zu bytes write at %px\n", size, do_nothing);
+ memcpy(do_nothing, do_almost_nothing, size);
+ pr_err("FAIL: survived bad write\n");
+
+ asm("" : "=m"(func));
+ func();
+}
+
void lkdtm_EXEC_DATA(void)
{
execute_location(data_area, CODE_WRITE);
diff --git a/tools/testing/selftests/lkdtm/tests.txt b/tools/testing/selftests/lkdtm/tests.txt
index 6b36b7f5dcf9..243c781f0780 100644
--- a/tools/testing/selftests/lkdtm/tests.txt
+++ b/tools/testing/selftests/lkdtm/tests.txt
@@ -44,6 +44,7 @@ ACCESS_NULL
WRITE_RO
WRITE_RO_AFTER_INIT
WRITE_KERN
+WRITE_OPD
REFCOUNT_INC_OVERFLOW
REFCOUNT_ADD_OVERFLOW
REFCOUNT_INC_NOT_ZERO_OVERFLOW
--
2.34.1
next prev parent reply other threads:[~2022-02-15 12:44 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 ` [PATCH v4 11/13] lkdtm: Really write into kernel text in WRITE_KERN Christophe Leroy
2022-02-15 12:41 ` [PATCH v4 12/13] lkdtm: Fix execute_[user]_location() Christophe Leroy
2022-02-15 12:41 ` Christophe Leroy [this message]
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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