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mirror of https://github.com/edk2-porting/linux-next.git synced 2024-12-23 04:34:11 +08:00

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 2016-06-03 12:06:52 -07:00
parent 9a49a528dc
commit aa981a665d

View File

@ -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");
}