From: Kees Cook <keescook@chromium.org>
To: kernel-hardening@lists.openwall.com
Cc: Kees Cook <keescook@chromium.org>, Arnd Bergmann <arnd@arndb.de>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
"David S. Miller" <davem@davemloft.net>,
Mauro Carvalho Chehab <mchehab@osg.samsung.com>,
Jiri Slaby <jslaby@suse.cz>, Guenter Roeck <linux@roeck-us.net>,
linux-kernel@vger.kernel.org
Subject: [PATCH 3/5] lkdtm: add function for testing .rodata section
Date: Tue, 7 Jun 2016 14:57:06 -0700 [thread overview]
Message-ID: <1465336628-18219-4-git-send-email-keescook@chromium.org> (raw)
In-Reply-To: <1465336628-18219-1-git-send-email-keescook@chromium.org>
This adds a function that lives in the .rodata section. The section
flags are corrected using objcopy since there is no way with gcc to
declare section flags in an architecture-agnostic way.
Signed-off-by: Kees Cook <keescook@chromium.org>
---
drivers/misc/Makefile | 7 +++++++
drivers/misc/lkdtm.h | 6 ++++++
drivers/misc/lkdtm_core.c | 24 +++++++++++++++++-------
drivers/misc/lkdtm_rodata.c | 10 ++++++++++
4 files changed, 40 insertions(+), 7 deletions(-)
create mode 100644 drivers/misc/lkdtm.h
create mode 100644 drivers/misc/lkdtm_rodata.c
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index c3cb6ad8cc37..b2d3d68dfa22 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -59,3 +59,10 @@ obj-$(CONFIG_CXL_BASE) += cxl/
obj-$(CONFIG_PANEL) += panel.o
lkdtm-$(CONFIG_LKDTM) += lkdtm_core.o
+lkdtm-$(CONFIG_LKDTM) += lkdtm_rodata_objcopy.o
+
+OBJCOPYFLAGS_lkdtm_rodata_objcopy.o := \
+ --set-section-flags .text=alloc,readonly \
+ --rename-section .text=.rodata
+$(obj)/lkdtm_rodata_objcopy.o: $(obj)/lkdtm_rodata.o
+ $(call if_changed,objcopy)
diff --git a/drivers/misc/lkdtm.h b/drivers/misc/lkdtm.h
new file mode 100644
index 000000000000..9531fa3be4c3
--- /dev/null
+++ b/drivers/misc/lkdtm.h
@@ -0,0 +1,6 @@
+#ifndef __LKDTM_H
+#define __LKDTM_H
+
+void lkdtm_rodata_do_nothing(void);
+
+#endif
diff --git a/drivers/misc/lkdtm_core.c b/drivers/misc/lkdtm_core.c
index 605050c60f10..187cd9b63e9a 100644
--- a/drivers/misc/lkdtm_core.c
+++ b/drivers/misc/lkdtm_core.c
@@ -52,6 +52,8 @@
#include <linux/ide.h>
#endif
+#include "lkdtm.h"
+
/*
* Make sure our attempts to over run the kernel stack doesn't trigger
* a compiler warning when CONFIG_FRAME_WARN is set. Then make sure we
@@ -103,6 +105,7 @@ enum ctype {
CT_EXEC_STACK,
CT_EXEC_KMALLOC,
CT_EXEC_VMALLOC,
+ CT_EXEC_RODATA,
CT_EXEC_USERSPACE,
CT_ACCESS_USERSPACE,
CT_WRITE_RO,
@@ -145,6 +148,7 @@ static char* cp_type[] = {
"EXEC_STACK",
"EXEC_KMALLOC",
"EXEC_VMALLOC",
+ "EXEC_RODATA",
"EXEC_USERSPACE",
"ACCESS_USERSPACE",
"WRITE_RO",
@@ -346,15 +350,18 @@ static noinline void corrupt_stack(void)
memset((void *)data, 0, 64);
}
-static void noinline execute_location(void *dst)
+static noinline void execute_location(void *dst, bool write)
{
void (*func)(void) = dst;
pr_info("attempting ok execution at %p\n", do_nothing);
do_nothing();
- memcpy(dst, do_nothing, EXEC_SIZE);
- flush_icache_range((unsigned long)dst, (unsigned long)dst + EXEC_SIZE);
+ if (write) {
+ memcpy(dst, do_nothing, EXEC_SIZE);
+ flush_icache_range((unsigned long)dst,
+ (unsigned long)dst + EXEC_SIZE);
+ }
pr_info("attempting bad execution at %p\n", func);
func();
}
@@ -551,25 +558,28 @@ static void lkdtm_do_action(enum ctype which)
schedule();
break;
case CT_EXEC_DATA:
- execute_location(data_area);
+ execute_location(data_area, true);
break;
case CT_EXEC_STACK: {
u8 stack_area[EXEC_SIZE];
- execute_location(stack_area);
+ execute_location(stack_area, true);
break;
}
case CT_EXEC_KMALLOC: {
u32 *kmalloc_area = kmalloc(EXEC_SIZE, GFP_KERNEL);
- execute_location(kmalloc_area);
+ execute_location(kmalloc_area, true);
kfree(kmalloc_area);
break;
}
case CT_EXEC_VMALLOC: {
u32 *vmalloc_area = vmalloc(EXEC_SIZE);
- execute_location(vmalloc_area);
+ execute_location(vmalloc_area, true);
vfree(vmalloc_area);
break;
}
+ case CT_EXEC_RODATA:
+ execute_location(lkdtm_rodata_do_nothing, false);
+ break;
case CT_EXEC_USERSPACE: {
unsigned long user_addr;
diff --git a/drivers/misc/lkdtm_rodata.c b/drivers/misc/lkdtm_rodata.c
new file mode 100644
index 000000000000..4d0d851f02b9
--- /dev/null
+++ b/drivers/misc/lkdtm_rodata.c
@@ -0,0 +1,10 @@
+/*
+ * This includes functions that are meant to live entirely in .rodata
+ * (via objcopy tricks), to validate the non-executability of .rodata.
+ */
+#include <linux/kernel.h>
+
+void lkdtm_rodata_do_nothing(void)
+{
+ /* Does nothing. We just want an architecture agnostic "return". */
+}
--
2.7.4
next prev parent reply other threads:[~2016-06-07 21:58 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-07 21:57 [PATCH 0/5] lkdtm: add usercopy and rodata, fix atomic Kees Cook
2016-06-07 21:57 ` [PATCH 1/5] lkdtm: split build into multiple source files Kees Cook
2016-06-07 21:57 ` [PATCH 2/5] lkdtm: clean up after rename Kees Cook
2016-06-07 21:57 ` Kees Cook [this message]
2016-06-08 1:02 ` [PATCH 3/5] lkdtm: add function for testing .rodata section Laura Abbott
2016-06-08 15:46 ` Kees Cook
2016-06-08 16:15 ` Laura Abbott
2016-06-08 21:26 ` Kees Cook
2016-06-10 1:14 ` Laura Abbott
[not found] ` <87h9b4oebf.fsf@concordia.ellerman.id.au>
2016-08-01 19:45 ` Linker segfault on powerpc when CONFIG_LKDTM=y (was Re: [kernel-hardening] [PATCH 3/5] lkdtm: add function for testing .rodata section) Kees Cook
2016-08-02 3:12 ` [kernel-hardening] " Michael Ellerman
2016-08-02 19:12 ` Kees Cook
2016-08-03 4:46 ` Michael Ellerman
2016-06-07 21:57 ` [PATCH 4/5] lkdtm: add usercopy tests Kees Cook
2016-06-07 23:36 ` kbuild test robot
2016-06-08 0:07 ` kbuild test robot
2016-06-07 21:57 ` [PATCH 5/5] lkdtm: split atomic test into over and underflow Kees Cook
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