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Subject[PATCH 03/12] lkdtm: split usercopy tests to separate file
Date
This splits the USERCOPY_* tests into the new lkdtm_usercopy.c file to
help separate things better for readability.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
drivers/misc/Makefile | 1 +
drivers/misc/lkdtm.h | 13 ++
drivers/misc/lkdtm_core.c | 280 ++-----------------------------------
drivers/misc/lkdtm_usercopy.c | 316 ++++++++++++++++++++++++++++++++++++++++++
4 files changed, 343 insertions(+), 267 deletions(-)
create mode 100644 drivers/misc/lkdtm_usercopy.c

diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index 7d45ed4a1549..e6b2778731ff 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -60,6 +60,7 @@ obj-$(CONFIG_PANEL) += panel.o

lkdtm-$(CONFIG_LKDTM) += lkdtm_core.o
lkdtm-$(CONFIG_LKDTM) += lkdtm_rodata_objcopy.o
+lkdtm-$(CONFIG_LKDTM) += lkdtm_usercopy.o

OBJCOPYFLAGS :=
OBJCOPYFLAGS_lkdtm_rodata_objcopy.o := \
diff --git a/drivers/misc/lkdtm.h b/drivers/misc/lkdtm.h
index 9531fa3be4c3..ef290a2c8816 100644
--- a/drivers/misc/lkdtm.h
+++ b/drivers/misc/lkdtm.h
@@ -1,6 +1,19 @@
#ifndef __LKDTM_H
#define __LKDTM_H

+/* lkdtm_rodata.c */
void lkdtm_rodata_do_nothing(void);

+/* lkdtm_usercopy.c */
+void __init lkdtm_usercopy_init(void);
+void __exit lkdtm_usercopy_exit(void);
+void lkdtm_USERCOPY_HEAP_SIZE_TO(void);
+void lkdtm_USERCOPY_HEAP_SIZE_FROM(void);
+void lkdtm_USERCOPY_HEAP_FLAG_TO(void);
+void lkdtm_USERCOPY_HEAP_FLAG_FROM(void);
+void lkdtm_USERCOPY_STACK_FRAME_TO(void);
+void lkdtm_USERCOPY_STACK_FRAME_FROM(void);
+void lkdtm_USERCOPY_STACK_BEYOND(void);
+void lkdtm_USERCOPY_KERNEL(void);
+
#endif
diff --git a/drivers/misc/lkdtm_core.c b/drivers/misc/lkdtm_core.c
index 80e7a46db178..74376920ed55 100644
--- a/drivers/misc/lkdtm_core.c
+++ b/drivers/misc/lkdtm_core.c
@@ -47,7 +47,6 @@
#include <linux/vmalloc.h>
#include <linux/mman.h>
#include <asm/cacheflush.h>
-#include <asm/sections.h>

#ifdef CONFIG_IDE
#include <linux/ide.h>
@@ -194,10 +193,6 @@ static DEFINE_SPINLOCK(lock_me_up);

static u8 data_area[EXEC_SIZE];

-static size_t cache_size = 1024;
-static struct kmem_cache *bad_cache;
-
-static const unsigned char test_text[] = "This is a test.\n";
static const unsigned long rodata = 0xAA55AA55;
static unsigned long ro_after_init __ro_after_init = 0x55AA5500;

@@ -404,255 +399,6 @@ static void execute_user_location(void *dst)
func();
}

-/*
- * Instead of adding -Wno-return-local-addr, just pass the stack address
- * through a function to obfuscate it from the compiler.
- */
-static noinline unsigned char *trick_compiler(unsigned char *stack)
-{
- return stack + 0;
-}
-
-static noinline unsigned char *do_usercopy_stack_callee(int value)
-{
- unsigned char buf[32];
- int i;
-
- /* Exercise stack to avoid everything living in registers. */
- for (i = 0; i < sizeof(buf); i++) {
- buf[i] = value & 0xff;
- }
-
- return trick_compiler(buf);
-}
-
-static noinline void do_usercopy_stack(bool to_user, bool bad_frame)
-{
- unsigned long user_addr;
- unsigned char good_stack[32];
- unsigned char *bad_stack;
- int i;
-
- /* Exercise stack to avoid everything living in registers. */
- for (i = 0; i < sizeof(good_stack); i++)
- good_stack[i] = test_text[i % sizeof(test_text)];
-
- /* This is a pointer to outside our current stack frame. */
- if (bad_frame) {
- bad_stack = do_usercopy_stack_callee((uintptr_t)bad_stack);
- } else {
- /* Put start address just inside stack. */
- bad_stack = task_stack_page(current) + THREAD_SIZE;
- bad_stack -= sizeof(unsigned long);
- }
-
- user_addr = vm_mmap(NULL, 0, PAGE_SIZE,
- PROT_READ | PROT_WRITE | PROT_EXEC,
- MAP_ANONYMOUS | MAP_PRIVATE, 0);
- if (user_addr >= TASK_SIZE) {
- pr_warn("Failed to allocate user memory\n");
- return;
- }
-
- if (to_user) {
- pr_info("attempting good copy_to_user of local stack\n");
- if (copy_to_user((void __user *)user_addr, good_stack,
- sizeof(good_stack))) {
- pr_warn("copy_to_user failed unexpectedly?!\n");
- goto free_user;
- }
-
- pr_info("attempting bad copy_to_user of distant stack\n");
- if (copy_to_user((void __user *)user_addr, bad_stack,
- sizeof(good_stack))) {
- pr_warn("copy_to_user failed, but lacked Oops\n");
- goto free_user;
- }
- } else {
- /*
- * There isn't a safe way to not be protected by usercopy
- * if we're going to write to another thread's stack.
- */
- if (!bad_frame)
- goto free_user;
-
- pr_info("attempting good copy_from_user of local stack\n");
- if (copy_from_user(good_stack, (void __user *)user_addr,
- sizeof(good_stack))) {
- pr_warn("copy_from_user failed unexpectedly?!\n");
- goto free_user;
- }
-
- pr_info("attempting bad copy_from_user of distant stack\n");
- if (copy_from_user(bad_stack, (void __user *)user_addr,
- sizeof(good_stack))) {
- pr_warn("copy_from_user failed, but lacked Oops\n");
- goto free_user;
- }
- }
-
-free_user:
- vm_munmap(user_addr, PAGE_SIZE);
-}
-
-static void do_usercopy_kernel(void)
-{
- unsigned long user_addr;
-
- user_addr = vm_mmap(NULL, 0, PAGE_SIZE,
- PROT_READ | PROT_WRITE | PROT_EXEC,
- MAP_ANONYMOUS | MAP_PRIVATE, 0);
- if (user_addr >= TASK_SIZE) {
- pr_warn("Failed to allocate user memory\n");
- return;
- }
-
- pr_info("attempting good copy_to_user from kernel rodata\n");
- if (copy_to_user((void __user *)user_addr, test_text,
- sizeof(test_text))) {
- pr_warn("copy_to_user failed unexpectedly?!\n");
- goto free_user;
- }
-
- pr_info("attempting bad copy_to_user from kernel text\n");
- if (copy_to_user((void __user *)user_addr, _stext, PAGE_SIZE)) {
- pr_warn("copy_to_user failed, but lacked Oops\n");
- goto free_user;
- }
-
-free_user:
- vm_munmap(user_addr, PAGE_SIZE);
-}
-
-static void do_usercopy_heap_size(bool to_user)
-{
- unsigned long user_addr;
- unsigned char *one, *two;
- size_t size = 1024;
-
- one = kmalloc(size, GFP_KERNEL);
- two = kmalloc(size, GFP_KERNEL);
- if (!one || !two) {
- pr_warn("Failed to allocate kernel memory\n");
- goto free_kernel;
- }
-
- user_addr = vm_mmap(NULL, 0, PAGE_SIZE,
- PROT_READ | PROT_WRITE | PROT_EXEC,
- MAP_ANONYMOUS | MAP_PRIVATE, 0);
- if (user_addr >= TASK_SIZE) {
- pr_warn("Failed to allocate user memory\n");
- goto free_kernel;
- }
-
- memset(one, 'A', size);
- memset(two, 'B', size);
-
- if (to_user) {
- pr_info("attempting good copy_to_user of correct size\n");
- if (copy_to_user((void __user *)user_addr, one, size)) {
- pr_warn("copy_to_user failed unexpectedly?!\n");
- goto free_user;
- }
-
- pr_info("attempting bad copy_to_user of too large size\n");
- if (copy_to_user((void __user *)user_addr, one, 2 * size)) {
- pr_warn("copy_to_user failed, but lacked Oops\n");
- goto free_user;
- }
- } else {
- pr_info("attempting good copy_from_user of correct size\n");
- if (copy_from_user(one, (void __user *)user_addr, size)) {
- pr_warn("copy_from_user failed unexpectedly?!\n");
- goto free_user;
- }
-
- pr_info("attempting bad copy_from_user of too large size\n");
- if (copy_from_user(one, (void __user *)user_addr, 2 * size)) {
- pr_warn("copy_from_user failed, but lacked Oops\n");
- goto free_user;
- }
- }
-
-free_user:
- vm_munmap(user_addr, PAGE_SIZE);
-free_kernel:
- kfree(one);
- kfree(two);
-}
-
-static void do_usercopy_heap_flag(bool to_user)
-{
- unsigned long user_addr;
- unsigned char *good_buf = NULL;
- unsigned char *bad_buf = NULL;
-
- /* Make sure cache was prepared. */
- if (!bad_cache) {
- pr_warn("Failed to allocate kernel cache\n");
- return;
- }
-
- /*
- * Allocate one buffer from each cache (kmalloc will have the
- * SLAB_USERCOPY flag already, but "bad_cache" won't).
- */
- good_buf = kmalloc(cache_size, GFP_KERNEL);
- bad_buf = kmem_cache_alloc(bad_cache, GFP_KERNEL);
- if (!good_buf || !bad_buf) {
- pr_warn("Failed to allocate buffers from caches\n");
- goto free_alloc;
- }
-
- /* Allocate user memory we'll poke at. */
- user_addr = vm_mmap(NULL, 0, PAGE_SIZE,
- PROT_READ | PROT_WRITE | PROT_EXEC,
- MAP_ANONYMOUS | MAP_PRIVATE, 0);
- if (user_addr >= TASK_SIZE) {
- pr_warn("Failed to allocate user memory\n");
- goto free_alloc;
- }
-
- memset(good_buf, 'A', cache_size);
- memset(bad_buf, 'B', cache_size);
-
- if (to_user) {
- pr_info("attempting good copy_to_user with SLAB_USERCOPY\n");
- if (copy_to_user((void __user *)user_addr, good_buf,
- cache_size)) {
- pr_warn("copy_to_user failed unexpectedly?!\n");
- goto free_user;
- }
-
- pr_info("attempting bad copy_to_user w/o SLAB_USERCOPY\n");
- if (copy_to_user((void __user *)user_addr, bad_buf,
- cache_size)) {
- pr_warn("copy_to_user failed, but lacked Oops\n");
- goto free_user;
- }
- } else {
- pr_info("attempting good copy_from_user with SLAB_USERCOPY\n");
- if (copy_from_user(good_buf, (void __user *)user_addr,
- cache_size)) {
- pr_warn("copy_from_user failed unexpectedly?!\n");
- goto free_user;
- }
-
- pr_info("attempting bad copy_from_user w/o SLAB_USERCOPY\n");
- if (copy_from_user(bad_buf, (void __user *)user_addr,
- cache_size)) {
- pr_warn("copy_from_user failed, but lacked Oops\n");
- goto free_user;
- }
- }
-
-free_user:
- vm_munmap(user_addr, PAGE_SIZE);
-free_alloc:
- if (bad_buf)
- kmem_cache_free(bad_cache, bad_buf);
- kfree(good_buf);
-}

static void lkdtm_do_action(enum ctype which)
{
@@ -965,28 +711,28 @@ static void lkdtm_do_action(enum ctype which)
return;
}
case CT_USERCOPY_HEAP_SIZE_TO:
- do_usercopy_heap_size(true);
+ lkdtm_USERCOPY_HEAP_SIZE_TO();
break;
case CT_USERCOPY_HEAP_SIZE_FROM:
- do_usercopy_heap_size(false);
+ lkdtm_USERCOPY_HEAP_SIZE_FROM();
break;
case CT_USERCOPY_HEAP_FLAG_TO:
- do_usercopy_heap_flag(true);
+ lkdtm_USERCOPY_HEAP_FLAG_TO();
break;
case CT_USERCOPY_HEAP_FLAG_FROM:
- do_usercopy_heap_flag(false);
+ lkdtm_USERCOPY_HEAP_FLAG_FROM();
break;
case CT_USERCOPY_STACK_FRAME_TO:
- do_usercopy_stack(true, true);
+ lkdtm_USERCOPY_STACK_FRAME_TO();
break;
case CT_USERCOPY_STACK_FRAME_FROM:
- do_usercopy_stack(false, true);
+ lkdtm_USERCOPY_STACK_FRAME_FROM();
break;
case CT_USERCOPY_STACK_BEYOND:
- do_usercopy_stack(true, false);
+ lkdtm_USERCOPY_STACK_BEYOND();
break;
case CT_USERCOPY_KERNEL:
- do_usercopy_kernel();
+ lkdtm_USERCOPY_KERNEL();
break;
case CT_NONE:
default:
@@ -1277,13 +1023,12 @@ static int __init lkdtm_module_init(void)
int n_debugfs_entries = 1; /* Assume only the direct entry */
int i;

+ /* Handle test-specific initialization. */
+ lkdtm_usercopy_init();
+
/* Make sure we can write to __ro_after_init values during __init */
ro_after_init |= 0xAA;

- /* Prepare cache that lacks SLAB_USERCOPY flag. */
- bad_cache = kmem_cache_create("lkdtm-no-usercopy", cache_size, 0,
- 0, NULL);
-
/* Register debugfs interface */
lkdtm_debugfs_root = debugfs_create_dir("provoke-crash", NULL);
if (!lkdtm_debugfs_root) {
@@ -1335,7 +1080,8 @@ static void __exit lkdtm_module_exit(void)
{
debugfs_remove_recursive(lkdtm_debugfs_root);

- kmem_cache_destroy(bad_cache);
+ /* Handle test-specific clean-up. */
+ lkdtm_usercopy_exit();

unregister_jprobe(&lkdtm);
pr_info("Crash point unregistered\n");
diff --git a/drivers/misc/lkdtm_usercopy.c b/drivers/misc/lkdtm_usercopy.c
new file mode 100644
index 000000000000..42ec6aa0dfb8
--- /dev/null
+++ b/drivers/misc/lkdtm_usercopy.c
@@ -0,0 +1,316 @@
+/*
+ * This is for all the tests related to copy_to_user() and copy_from_user()
+ * hardening.
+ */
+#define pr_fmt(fmt) "lkdtm: " fmt
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+#include <linux/mman.h>
+#include <linux/uaccess.h>
+#include <asm/cacheflush.h>
+#include <asm/sections.h>
+
+static size_t cache_size = 1024;
+static struct kmem_cache *bad_cache;
+
+static const unsigned char test_text[] = "This is a test.\n";
+
+/*
+ * Instead of adding -Wno-return-local-addr, just pass the stack address
+ * through a function to obfuscate it from the compiler.
+ */
+static noinline unsigned char *trick_compiler(unsigned char *stack)
+{
+ return stack + 0;
+}
+
+static noinline unsigned char *do_usercopy_stack_callee(int value)
+{
+ unsigned char buf[32];
+ int i;
+
+ /* Exercise stack to avoid everything living in registers. */
+ for (i = 0; i < sizeof(buf); i++) {
+ buf[i] = value & 0xff;
+ }
+
+ return trick_compiler(buf);
+}
+
+static noinline void do_usercopy_stack(bool to_user, bool bad_frame)
+{
+ unsigned long user_addr;
+ unsigned char good_stack[32];
+ unsigned char *bad_stack;
+ int i;
+
+ /* Exercise stack to avoid everything living in registers. */
+ for (i = 0; i < sizeof(good_stack); i++)
+ good_stack[i] = test_text[i % sizeof(test_text)];
+
+ /* This is a pointer to outside our current stack frame. */
+ if (bad_frame) {
+ bad_stack = do_usercopy_stack_callee((uintptr_t)bad_stack);
+ } else {
+ /* Put start address just inside stack. */
+ bad_stack = task_stack_page(current) + THREAD_SIZE;
+ bad_stack -= sizeof(unsigned long);
+ }
+
+ user_addr = vm_mmap(NULL, 0, PAGE_SIZE,
+ PROT_READ | PROT_WRITE | PROT_EXEC,
+ MAP_ANONYMOUS | MAP_PRIVATE, 0);
+ if (user_addr >= TASK_SIZE) {
+ pr_warn("Failed to allocate user memory\n");
+ return;
+ }
+
+ if (to_user) {
+ pr_info("attempting good copy_to_user of local stack\n");
+ if (copy_to_user((void __user *)user_addr, good_stack,
+ sizeof(good_stack))) {
+ pr_warn("copy_to_user failed unexpectedly?!\n");
+ goto free_user;
+ }
+
+ pr_info("attempting bad copy_to_user of distant stack\n");
+ if (copy_to_user((void __user *)user_addr, bad_stack,
+ sizeof(good_stack))) {
+ pr_warn("copy_to_user failed, but lacked Oops\n");
+ goto free_user;
+ }
+ } else {
+ /*
+ * There isn't a safe way to not be protected by usercopy
+ * if we're going to write to another thread's stack.
+ */
+ if (!bad_frame)
+ goto free_user;
+
+ pr_info("attempting good copy_from_user of local stack\n");
+ if (copy_from_user(good_stack, (void __user *)user_addr,
+ sizeof(good_stack))) {
+ pr_warn("copy_from_user failed unexpectedly?!\n");
+ goto free_user;
+ }
+
+ pr_info("attempting bad copy_from_user of distant stack\n");
+ if (copy_from_user(bad_stack, (void __user *)user_addr,
+ sizeof(good_stack))) {
+ pr_warn("copy_from_user failed, but lacked Oops\n");
+ goto free_user;
+ }
+ }
+
+free_user:
+ vm_munmap(user_addr, PAGE_SIZE);
+}
+
+static void do_usercopy_heap_size(bool to_user)
+{
+ unsigned long user_addr;
+ unsigned char *one, *two;
+ const size_t size = 1024;
+
+ one = kmalloc(size, GFP_KERNEL);
+ two = kmalloc(size, GFP_KERNEL);
+ if (!one || !two) {
+ pr_warn("Failed to allocate kernel memory\n");
+ goto free_kernel;
+ }
+
+ user_addr = vm_mmap(NULL, 0, PAGE_SIZE,
+ PROT_READ | PROT_WRITE | PROT_EXEC,
+ MAP_ANONYMOUS | MAP_PRIVATE, 0);
+ if (user_addr >= TASK_SIZE) {
+ pr_warn("Failed to allocate user memory\n");
+ goto free_kernel;
+ }
+
+ memset(one, 'A', size);
+ memset(two, 'B', size);
+
+ if (to_user) {
+ pr_info("attempting good copy_to_user of correct size\n");
+ if (copy_to_user((void __user *)user_addr, one, size)) {
+ pr_warn("copy_to_user failed unexpectedly?!\n");
+ goto free_user;
+ }
+
+ pr_info("attempting bad copy_to_user of too large size\n");
+ if (copy_to_user((void __user *)user_addr, one, 2 * size)) {
+ pr_warn("copy_to_user failed, but lacked Oops\n");
+ goto free_user;
+ }
+ } else {
+ pr_info("attempting good copy_from_user of correct size\n");
+ if (copy_from_user(one, (void __user *)user_addr, size)) {
+ pr_warn("copy_from_user failed unexpectedly?!\n");
+ goto free_user;
+ }
+
+ pr_info("attempting bad copy_from_user of too large size\n");
+ if (copy_from_user(one, (void __user *)user_addr, 2 * size)) {
+ pr_warn("copy_from_user failed, but lacked Oops\n");
+ goto free_user;
+ }
+ }
+
+free_user:
+ vm_munmap(user_addr, PAGE_SIZE);
+free_kernel:
+ kfree(one);
+ kfree(two);
+}
+
+static void do_usercopy_heap_flag(bool to_user)
+{
+ unsigned long user_addr;
+ unsigned char *good_buf = NULL;
+ unsigned char *bad_buf = NULL;
+
+ /* Make sure cache was prepared. */
+ if (!bad_cache) {
+ pr_warn("Failed to allocate kernel cache\n");
+ return;
+ }
+
+ /*
+ * Allocate one buffer from each cache (kmalloc will have the
+ * SLAB_USERCOPY flag already, but "bad_cache" won't).
+ */
+ good_buf = kmalloc(cache_size, GFP_KERNEL);
+ bad_buf = kmem_cache_alloc(bad_cache, GFP_KERNEL);
+ if (!good_buf || !bad_buf) {
+ pr_warn("Failed to allocate buffers from caches\n");
+ goto free_alloc;
+ }
+
+ /* Allocate user memory we'll poke at. */
+ user_addr = vm_mmap(NULL, 0, PAGE_SIZE,
+ PROT_READ | PROT_WRITE | PROT_EXEC,
+ MAP_ANONYMOUS | MAP_PRIVATE, 0);
+ if (user_addr >= TASK_SIZE) {
+ pr_warn("Failed to allocate user memory\n");
+ goto free_alloc;
+ }
+
+ memset(good_buf, 'A', cache_size);
+ memset(bad_buf, 'B', cache_size);
+
+ if (to_user) {
+ pr_info("attempting good copy_to_user with SLAB_USERCOPY\n");
+ if (copy_to_user((void __user *)user_addr, good_buf,
+ cache_size)) {
+ pr_warn("copy_to_user failed unexpectedly?!\n");
+ goto free_user;
+ }
+
+ pr_info("attempting bad copy_to_user w/o SLAB_USERCOPY\n");
+ if (copy_to_user((void __user *)user_addr, bad_buf,
+ cache_size)) {
+ pr_warn("copy_to_user failed, but lacked Oops\n");
+ goto free_user;
+ }
+ } else {
+ pr_info("attempting good copy_from_user with SLAB_USERCOPY\n");
+ if (copy_from_user(good_buf, (void __user *)user_addr,
+ cache_size)) {
+ pr_warn("copy_from_user failed unexpectedly?!\n");
+ goto free_user;
+ }
+
+ pr_info("attempting bad copy_from_user w/o SLAB_USERCOPY\n");
+ if (copy_from_user(bad_buf, (void __user *)user_addr,
+ cache_size)) {
+ pr_warn("copy_from_user failed, but lacked Oops\n");
+ goto free_user;
+ }
+ }
+
+free_user:
+ vm_munmap(user_addr, PAGE_SIZE);
+free_alloc:
+ if (bad_buf)
+ kmem_cache_free(bad_cache, bad_buf);
+ kfree(good_buf);
+}
+
+/* Callable tests. */
+void lkdtm_USERCOPY_HEAP_SIZE_TO(void)
+{
+ do_usercopy_heap_size(true);
+}
+
+void lkdtm_USERCOPY_HEAP_SIZE_FROM(void)
+{
+ do_usercopy_heap_size(false);
+}
+
+void lkdtm_USERCOPY_HEAP_FLAG_TO(void)
+{
+ do_usercopy_heap_flag(true);
+}
+
+void lkdtm_USERCOPY_HEAP_FLAG_FROM(void)
+{
+ do_usercopy_heap_flag(false);
+}
+
+void lkdtm_USERCOPY_STACK_FRAME_TO(void)
+{
+ do_usercopy_stack(true, true);
+}
+
+void lkdtm_USERCOPY_STACK_FRAME_FROM(void)
+{
+ do_usercopy_stack(false, true);
+}
+
+void lkdtm_USERCOPY_STACK_BEYOND(void)
+{
+ do_usercopy_stack(true, false);
+}
+
+void lkdtm_USERCOPY_KERNEL(void)
+{
+ unsigned long user_addr;
+
+ user_addr = vm_mmap(NULL, 0, PAGE_SIZE,
+ PROT_READ | PROT_WRITE | PROT_EXEC,
+ MAP_ANONYMOUS | MAP_PRIVATE, 0);
+ if (user_addr >= TASK_SIZE) {
+ pr_warn("Failed to allocate user memory\n");
+ return;
+ }
+
+ pr_info("attempting good copy_to_user from kernel rodata\n");
+ if (copy_to_user((void __user *)user_addr, test_text,
+ sizeof(test_text))) {
+ pr_warn("copy_to_user failed unexpectedly?!\n");
+ goto free_user;
+ }
+
+ pr_info("attempting bad copy_to_user from kernel text\n");
+ if (copy_to_user((void __user *)user_addr, _stext, PAGE_SIZE)) {
+ pr_warn("copy_to_user failed, but lacked Oops\n");
+ goto free_user;
+ }
+
+free_user:
+ vm_munmap(user_addr, PAGE_SIZE);
+}
+
+void __init lkdtm_usercopy_init(void)
+{
+ /* Prepare cache that lacks SLAB_USERCOPY flag. */
+ bad_cache = kmem_cache_create("lkdtm-no-usercopy", cache_size, 0,
+ 0, NULL);
+}
+
+void __exit lkdtm_usercopy_exit(void)
+{
+ kmem_cache_destroy(bad_cache);
+}
--
2.7.4
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