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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-09-12 05:48:40 +00:00
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:
parent
9a49a528dc
commit
aa981a665d
1 changed files with 273 additions and 2 deletions
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@ -111,7 +111,14 @@ enum ctype {
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CT_WRITE_RO,
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CT_WRITE_RO_AFTER_INIT,
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CT_WRITE_KERN,
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CT_WRAP_ATOMIC
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CT_WRAP_ATOMIC,
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CT_USERCOPY_HEAP_SIZE_TO,
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CT_USERCOPY_HEAP_SIZE_FROM,
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CT_USERCOPY_HEAP_FLAG_TO,
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CT_USERCOPY_HEAP_FLAG_FROM,
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CT_USERCOPY_STACK_FRAME_TO,
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CT_USERCOPY_STACK_FRAME_FROM,
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CT_USERCOPY_STACK_BEYOND,
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};
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static char* cp_name[] = {
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@ -154,7 +161,14 @@ static char* cp_type[] = {
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"WRITE_RO",
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"WRITE_RO_AFTER_INIT",
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"WRITE_KERN",
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"WRAP_ATOMIC"
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"WRAP_ATOMIC",
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"USERCOPY_HEAP_SIZE_TO",
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"USERCOPY_HEAP_SIZE_FROM",
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"USERCOPY_HEAP_FLAG_TO",
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"USERCOPY_HEAP_FLAG_FROM",
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"USERCOPY_STACK_FRAME_TO",
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"USERCOPY_STACK_FRAME_FROM",
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"USERCOPY_STACK_BEYOND",
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};
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static struct jprobe lkdtm;
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@ -166,6 +180,8 @@ static char* cpoint_name;
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static char* cpoint_type;
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static int cpoint_count = DEFAULT_COUNT;
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static int recur_count = REC_NUM_DEFAULT;
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static int alloc_size = 1024;
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static size_t cache_size;
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static enum cname cpoint = CN_INVALID;
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static enum ctype cptype = CT_NONE;
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@ -174,7 +190,9 @@ static DEFINE_SPINLOCK(count_lock);
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static DEFINE_SPINLOCK(lock_me_up);
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static u8 data_area[EXEC_SIZE];
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static struct kmem_cache *bad_cache;
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static const unsigned char test_text[] = "This is a test.\n";
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static const unsigned long rodata = 0xAA55AA55;
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static unsigned long ro_after_init __ro_after_init = 0x55AA5500;
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@ -188,6 +206,9 @@ MODULE_PARM_DESC(cpoint_type, " Crash Point Type, action to be taken on "\
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module_param(cpoint_count, int, 0644);
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MODULE_PARM_DESC(cpoint_count, " Crash Point Count, number of times the "\
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"crash point is to be hit to trigger action");
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module_param(alloc_size, int, 0644);
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MODULE_PARM_DESC(alloc_size, " Size of allocation for user copy tests "\
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"(from 1 to PAGE_SIZE)");
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static unsigned int jp_do_irq(unsigned int irq)
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{
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@ -381,6 +402,228 @@ static void execute_user_location(void *dst)
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func();
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}
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/*
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* Instead of adding -Wno-return-local-addr, just pass the stack address
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* through a function to obfuscate it from the compiler.
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*/
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static noinline unsigned char *trick_compiler(unsigned char *stack)
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{
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return stack + 0;
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}
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static noinline unsigned char *do_usercopy_stack_callee(int value)
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{
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unsigned char buf[32];
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int i;
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/* Exercise stack to avoid everything living in registers. */
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for (i = 0; i < sizeof(buf); i++) {
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buf[i] = value & 0xff;
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}
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return trick_compiler(buf);
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}
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static noinline void do_usercopy_stack(bool to_user, bool bad_frame)
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{
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unsigned long user_addr;
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unsigned char good_stack[32];
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unsigned char *bad_stack;
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int i;
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/* Exercise stack to avoid everything living in registers. */
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for (i = 0; i < sizeof(good_stack); i++)
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good_stack[i] = test_text[i % sizeof(test_text)];
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/* This is a pointer to outside our current stack frame. */
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if (bad_frame) {
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bad_stack = do_usercopy_stack_callee(alloc_size);
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} else {
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/* Put start address just inside stack. */
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bad_stack = task_stack_page(current) + THREAD_SIZE;
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bad_stack -= sizeof(unsigned long);
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}
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user_addr = vm_mmap(NULL, 0, PAGE_SIZE,
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PROT_READ | PROT_WRITE | PROT_EXEC,
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MAP_ANONYMOUS | MAP_PRIVATE, 0);
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if (user_addr >= TASK_SIZE) {
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pr_warn("Failed to allocate user memory\n");
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return;
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}
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if (to_user) {
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pr_info("attempting good copy_to_user of local stack\n");
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if (copy_to_user((void __user *)user_addr, good_stack,
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sizeof(good_stack))) {
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pr_warn("copy_to_user failed unexpectedly?!\n");
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goto free_user;
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}
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pr_info("attempting bad copy_to_user of distant stack\n");
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if (copy_to_user((void __user *)user_addr, bad_stack,
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sizeof(good_stack))) {
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pr_warn("copy_to_user failed, but lacked Oops\n");
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goto free_user;
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}
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} else {
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/*
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* There isn't a safe way to not be protected by usercopy
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* if we're going to write to another thread's stack.
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*/
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if (!bad_frame)
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goto free_user;
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pr_info("attempting good copy_from_user of local stack\n");
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if (copy_from_user(good_stack, (void __user *)user_addr,
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sizeof(good_stack))) {
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pr_warn("copy_from_user failed unexpectedly?!\n");
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goto free_user;
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}
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pr_info("attempting bad copy_from_user of distant stack\n");
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if (copy_from_user(bad_stack, (void __user *)user_addr,
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sizeof(good_stack))) {
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pr_warn("copy_from_user failed, but lacked Oops\n");
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goto free_user;
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}
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}
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free_user:
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vm_munmap(user_addr, PAGE_SIZE);
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}
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static void do_usercopy_heap_size(bool to_user)
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{
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unsigned long user_addr;
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unsigned char *one, *two;
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size_t size = clamp_t(int, alloc_size, 1, PAGE_SIZE);
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one = kmalloc(size, GFP_KERNEL);
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two = kmalloc(size, GFP_KERNEL);
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if (!one || !two) {
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pr_warn("Failed to allocate kernel memory\n");
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goto free_kernel;
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}
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user_addr = vm_mmap(NULL, 0, PAGE_SIZE,
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PROT_READ | PROT_WRITE | PROT_EXEC,
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MAP_ANONYMOUS | MAP_PRIVATE, 0);
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if (user_addr >= TASK_SIZE) {
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pr_warn("Failed to allocate user memory\n");
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goto free_kernel;
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}
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memset(one, 'A', size);
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memset(two, 'B', size);
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if (to_user) {
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pr_info("attempting good copy_to_user of correct size\n");
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if (copy_to_user((void __user *)user_addr, one, size)) {
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pr_warn("copy_to_user failed unexpectedly?!\n");
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goto free_user;
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}
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pr_info("attempting bad copy_to_user of too large size\n");
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if (copy_to_user((void __user *)user_addr, one, 2 * size)) {
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pr_warn("copy_to_user failed, but lacked Oops\n");
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goto free_user;
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}
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} else {
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pr_info("attempting good copy_from_user of correct size\n");
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if (copy_from_user(one, (void __user *)user_addr,
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size)) {
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pr_warn("copy_from_user failed unexpectedly?!\n");
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goto free_user;
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}
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pr_info("attempting bad copy_from_user of too large size\n");
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if (copy_from_user(one, (void __user *)user_addr, 2 * size)) {
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pr_warn("copy_from_user failed, but lacked Oops\n");
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goto free_user;
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}
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}
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free_user:
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vm_munmap(user_addr, PAGE_SIZE);
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free_kernel:
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kfree(one);
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kfree(two);
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}
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static void do_usercopy_heap_flag(bool to_user)
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{
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unsigned long user_addr;
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unsigned char *good_buf = NULL;
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unsigned char *bad_buf = NULL;
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/* Make sure cache was prepared. */
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if (!bad_cache) {
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pr_warn("Failed to allocate kernel cache\n");
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return;
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}
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/*
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* Allocate one buffer from each cache (kmalloc will have the
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* SLAB_USERCOPY flag already, but "bad_cache" won't).
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*/
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good_buf = kmalloc(cache_size, GFP_KERNEL);
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bad_buf = kmem_cache_alloc(bad_cache, GFP_KERNEL);
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if (!good_buf || !bad_buf) {
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pr_warn("Failed to allocate buffers from caches\n");
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goto free_alloc;
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}
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/* Allocate user memory we'll poke at. */
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user_addr = vm_mmap(NULL, 0, PAGE_SIZE,
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PROT_READ | PROT_WRITE | PROT_EXEC,
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MAP_ANONYMOUS | MAP_PRIVATE, 0);
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if (user_addr >= TASK_SIZE) {
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pr_warn("Failed to allocate user memory\n");
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goto free_alloc;
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}
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memset(good_buf, 'A', cache_size);
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memset(bad_buf, 'B', cache_size);
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if (to_user) {
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pr_info("attempting good copy_to_user with SLAB_USERCOPY\n");
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if (copy_to_user((void __user *)user_addr, good_buf,
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cache_size)) {
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pr_warn("copy_to_user failed unexpectedly?!\n");
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goto free_user;
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}
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pr_info("attempting bad copy_to_user w/o SLAB_USERCOPY\n");
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if (copy_to_user((void __user *)user_addr, bad_buf,
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cache_size)) {
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pr_warn("copy_to_user failed, but lacked Oops\n");
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goto free_user;
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}
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} else {
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pr_info("attempting good copy_from_user with SLAB_USERCOPY\n");
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if (copy_from_user(good_buf, (void __user *)user_addr,
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cache_size)) {
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pr_warn("copy_from_user failed unexpectedly?!\n");
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goto free_user;
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}
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pr_info("attempting bad copy_from_user w/o SLAB_USERCOPY\n");
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if (copy_from_user(bad_buf, (void __user *)user_addr,
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cache_size)) {
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pr_warn("copy_from_user failed, but lacked Oops\n");
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goto free_user;
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}
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}
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free_user:
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vm_munmap(user_addr, PAGE_SIZE);
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free_alloc:
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if (bad_buf)
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kmem_cache_free(bad_cache, bad_buf);
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kfree(good_buf);
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}
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static void lkdtm_do_action(enum ctype which)
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{
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switch (which) {
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@ -679,6 +922,27 @@ static void lkdtm_do_action(enum ctype which)
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return;
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}
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case CT_USERCOPY_HEAP_SIZE_TO:
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do_usercopy_heap_size(true);
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break;
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case CT_USERCOPY_HEAP_SIZE_FROM:
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do_usercopy_heap_size(false);
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break;
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case CT_USERCOPY_HEAP_FLAG_TO:
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do_usercopy_heap_flag(true);
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break;
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case CT_USERCOPY_HEAP_FLAG_FROM:
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do_usercopy_heap_flag(false);
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break;
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case CT_USERCOPY_STACK_FRAME_TO:
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do_usercopy_stack(true, true);
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break;
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case CT_USERCOPY_STACK_FRAME_FROM:
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do_usercopy_stack(false, true);
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break;
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case CT_USERCOPY_STACK_BEYOND:
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do_usercopy_stack(true, false);
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break;
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case CT_NONE:
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default:
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break;
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@ -971,6 +1235,11 @@ static int __init lkdtm_module_init(void)
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/* Make sure we can write to __ro_after_init values during __init */
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ro_after_init |= 0xAA;
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/* Prepare cache that lacks SLAB_USERCOPY flag. */
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cache_size = clamp_t(int, alloc_size, 1, PAGE_SIZE);
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bad_cache = kmem_cache_create("lkdtm-no-usercopy", cache_size, 0,
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0, NULL);
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/* Register debugfs interface */
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lkdtm_debugfs_root = debugfs_create_dir("provoke-crash", NULL);
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if (!lkdtm_debugfs_root) {
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@ -1022,6 +1291,8 @@ static void __exit lkdtm_module_exit(void)
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{
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debugfs_remove_recursive(lkdtm_debugfs_root);
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kmem_cache_destroy(bad_cache);
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unregister_jprobe(&lkdtm);
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pr_info("Crash point unregistered\n");
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}
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