lkdtm: add usercopy tests
This adds test to detect copy_to_user/copy_from_user problems that are protected by PAX_USERCOPY (and will be protected by HARDENED_USERCOPY). Explicitly tests both "to" and "from" directions of heap object size problems, heap object markings and, stack frame misalignment. Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Kees Cook
parent
9a49a528dc
commit
aa981a665d
|
|
@ -111,7 +111,14 @@ enum ctype {
|
|||
CT_WRITE_RO,
|
||||
CT_WRITE_RO_AFTER_INIT,
|
||||
CT_WRITE_KERN,
|
||||
CT_WRAP_ATOMIC
|
||||
CT_WRAP_ATOMIC,
|
||||
CT_USERCOPY_HEAP_SIZE_TO,
|
||||
CT_USERCOPY_HEAP_SIZE_FROM,
|
||||
CT_USERCOPY_HEAP_FLAG_TO,
|
||||
CT_USERCOPY_HEAP_FLAG_FROM,
|
||||
CT_USERCOPY_STACK_FRAME_TO,
|
||||
CT_USERCOPY_STACK_FRAME_FROM,
|
||||
CT_USERCOPY_STACK_BEYOND,
|
||||
};
|
||||
|
||||
static char* cp_name[] = {
|
||||
|
|
@ -154,7 +161,14 @@ static char* cp_type[] = {
|
|||
"WRITE_RO",
|
||||
"WRITE_RO_AFTER_INIT",
|
||||
"WRITE_KERN",
|
||||
"WRAP_ATOMIC"
|
||||
"WRAP_ATOMIC",
|
||||
"USERCOPY_HEAP_SIZE_TO",
|
||||
"USERCOPY_HEAP_SIZE_FROM",
|
||||
"USERCOPY_HEAP_FLAG_TO",
|
||||
"USERCOPY_HEAP_FLAG_FROM",
|
||||
"USERCOPY_STACK_FRAME_TO",
|
||||
"USERCOPY_STACK_FRAME_FROM",
|
||||
"USERCOPY_STACK_BEYOND",
|
||||
};
|
||||
|
||||
static struct jprobe lkdtm;
|
||||
|
|
@ -166,6 +180,8 @@ static char* cpoint_name;
|
|||
static char* cpoint_type;
|
||||
static int cpoint_count = DEFAULT_COUNT;
|
||||
static int recur_count = REC_NUM_DEFAULT;
|
||||
static int alloc_size = 1024;
|
||||
static size_t cache_size;
|
||||
|
||||
static enum cname cpoint = CN_INVALID;
|
||||
static enum ctype cptype = CT_NONE;
|
||||
|
|
@ -174,7 +190,9 @@ static DEFINE_SPINLOCK(count_lock);
|
|||
static DEFINE_SPINLOCK(lock_me_up);
|
||||
|
||||
static u8 data_area[EXEC_SIZE];
|
||||
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;
|
||||
|
||||
|
|
@ -188,6 +206,9 @@ MODULE_PARM_DESC(cpoint_type, " Crash Point Type, action to be taken on "\
|
|||
module_param(cpoint_count, int, 0644);
|
||||
MODULE_PARM_DESC(cpoint_count, " Crash Point Count, number of times the "\
|
||||
"crash point is to be hit to trigger action");
|
||||
module_param(alloc_size, int, 0644);
|
||||
MODULE_PARM_DESC(alloc_size, " Size of allocation for user copy tests "\
|
||||
"(from 1 to PAGE_SIZE)");
|
||||
|
||||
static unsigned int jp_do_irq(unsigned int irq)
|
||||
{
|
||||
|
|
@ -381,6 +402,228 @@ 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(alloc_size);
|
||||
} 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;
|
||||
size_t size = clamp_t(int, alloc_size, 1, PAGE_SIZE);
|
||||
|
||||
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)
|
||||
{
|
||||
switch (which) {
|
||||
|
|
@ -679,6 +922,27 @@ static void lkdtm_do_action(enum ctype which)
|
|||
|
||||
return;
|
||||
}
|
||||
case CT_USERCOPY_HEAP_SIZE_TO:
|
||||
do_usercopy_heap_size(true);
|
||||
break;
|
||||
case CT_USERCOPY_HEAP_SIZE_FROM:
|
||||
do_usercopy_heap_size(false);
|
||||
break;
|
||||
case CT_USERCOPY_HEAP_FLAG_TO:
|
||||
do_usercopy_heap_flag(true);
|
||||
break;
|
||||
case CT_USERCOPY_HEAP_FLAG_FROM:
|
||||
do_usercopy_heap_flag(false);
|
||||
break;
|
||||
case CT_USERCOPY_STACK_FRAME_TO:
|
||||
do_usercopy_stack(true, true);
|
||||
break;
|
||||
case CT_USERCOPY_STACK_FRAME_FROM:
|
||||
do_usercopy_stack(false, true);
|
||||
break;
|
||||
case CT_USERCOPY_STACK_BEYOND:
|
||||
do_usercopy_stack(true, false);
|
||||
break;
|
||||
case CT_NONE:
|
||||
default:
|
||||
break;
|
||||
|
|
@ -971,6 +1235,11 @@ static int __init lkdtm_module_init(void)
|
|||
/* Make sure we can write to __ro_after_init values during __init */
|
||||
ro_after_init |= 0xAA;
|
||||
|
||||
/* Prepare cache that lacks SLAB_USERCOPY flag. */
|
||||
cache_size = clamp_t(int, alloc_size, 1, PAGE_SIZE);
|
||||
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) {
|
||||
|
|
@ -1022,6 +1291,8 @@ static void __exit lkdtm_module_exit(void)
|
|||
{
|
||||
debugfs_remove_recursive(lkdtm_debugfs_root);
|
||||
|
||||
kmem_cache_destroy(bad_cache);
|
||||
|
||||
unregister_jprobe(&lkdtm);
|
||||
pr_info("Crash point unregistered\n");
|
||||
}
|
||||
|
|
|
|||
Loading…
Reference in New Issue