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lkdtm: add function for testing .rodata section

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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>
This commit is contained in:
Kees Cook 2016-02-22 14:09:29 -08:00
parent 426f3a53d4
commit 9a49a528dc
4 changed files with 41 additions and 7 deletions
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8
drivers/misc/Makefile
View File

@ -59,3 +59,11 @@ obj-$(CONFIG_CXL_BASE) += cxl/
obj-$(CONFIG_PANEL) += panel.o
lkdtm-$(CONFIG_LKDTM) += lkdtm_core.o
lkdtm-$(CONFIG_LKDTM) += lkdtm_rodata_objcopy.o
OBJCOPYFLAGS :=
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)

6
drivers/misc/lkdtm.h Normal file
View File

@ -0,0 +1,6 @@
#ifndef __LKDTM_H
#define __LKDTM_H
void lkdtm_rodata_do_nothing(void);
#endif

24
drivers/misc/lkdtm_core.c
View File

@ -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;

10
drivers/misc/lkdtm_rodata.c Normal file
View File

@ -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". */
}