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: Christophe Leroy <christophe.leroy@csgroup.eu>,
linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
linux-ia64@vger.kernel.org, linux-parisc@vger.kernel.org,
linux-arch@vger.kernel.org, linux-mm@kvack.org
Subject: [PATCH v3 12/12] lkdtm: Add a test for function descriptors protection
Date: Sun, 17 Oct 2021 14:38:25 +0200 [thread overview]
Message-ID: <67f9545c9ad15048bfe0104278ef9595d051dbc8.1634457599.git.christophe.leroy@csgroup.eu> (raw)
In-Reply-To: <cover.1634457599.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>
---
drivers/misc/lkdtm/core.c | 1 +
drivers/misc/lkdtm/lkdtm.h | 1 +
drivers/misc/lkdtm/perms.c | 22 ++++++++++++++++++++++
3 files changed, 24 insertions(+)
diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c
index fe6fd34b8caf..de092aa03b5d 100644
--- a/drivers/misc/lkdtm/core.c
+++ b/drivers/misc/lkdtm/core.c
@@ -148,6 +148,7 @@ 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 c212a253edde..188bd0fd6575 100644
--- a/drivers/misc/lkdtm/lkdtm.h
+++ b/drivers/misc/lkdtm/lkdtm.h
@@ -105,6 +105,7 @@ 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);
--
2.31.1
next prev parent reply other threads:[~2021-10-17 12:40 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
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 ` Christophe Leroy [this message]
2022-02-11 1:09 ` [PATCH v3 12/12] lkdtm: Add a test for function descriptors protection Kees Cook
2022-02-14 10:34 ` Christophe Leroy
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=67f9545c9ad15048bfe0104278ef9595d051dbc8.1634457599.git.christophe.leroy@csgroup.eu \
--to=christophe.leroy@csgroup.eu \
--cc=James.Bottomley@HansenPartnership.com \
--cc=akpm@linux-foundation.org \
--cc=arnd@arndb.de \
--cc=benh@kernel.crashing.org \
--cc=deller@gmx.de \
--cc=gregkh@linuxfoundation.org \
--cc=keescook@chromium.org \
--cc=linux-arch@vger.kernel.org \
--cc=linux-ia64@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux-parisc@vger.kernel.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=mpe@ellerman.id.au \
--cc=paulus@samba.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).