Author | Tokens | Token Proportion | Commits | Commit Proportion |
---|---|---|---|---|
Kees Cook | 1281 | 94.33% | 6 | 66.67% |
Jann Horn | 73 | 5.38% | 1 | 11.11% |
Ingo Molnar | 3 | 0.22% | 1 | 11.11% |
Greg Kroah-Hartman | 1 | 0.07% | 1 | 11.11% |
Total | 1358 | 9 |
// SPDX-License-Identifier: GPL-2.0 /* * This is for all the tests related to copy_to_user() and copy_from_user() * hardening. */ #include "lkdtm.h" #include <linux/slab.h> #include <linux/vmalloc.h> #include <linux/sched/task_stack.h> #include <linux/mman.h> #include <linux/uaccess.h> #include <asm/cacheflush.h> /* * Many of the tests here end up using const sizes, but those would * normally be ignored by hardened usercopy, so force the compiler * into choosing the non-const path to make sure we trigger the * hardened usercopy checks by added "unconst" to all the const copies, * and making sure "cache_size" isn't optimized into a const. */ static volatile size_t unconst; static volatile size_t cache_size = 1024; static struct kmem_cache *whitelist_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, unconst + 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, unconst + 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, unconst + 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, unconst + sizeof(good_stack))) { pr_warn("copy_from_user failed, but lacked Oops\n"); goto free_user; } } free_user: vm_munmap(user_addr, PAGE_SIZE); } /* * This checks for whole-object size validation with hardened usercopy, * with or without usercopy whitelisting. */ static void do_usercopy_heap_size(bool to_user) { unsigned long user_addr; unsigned char *one, *two; void __user *test_user_addr; void *test_kern_addr; size_t size = unconst + 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); test_user_addr = (void __user *)(user_addr + 16); test_kern_addr = one + 16; if (to_user) { pr_info("attempting good copy_to_user of correct size\n"); if (copy_to_user(test_user_addr, test_kern_addr, size / 2)) { 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(test_user_addr, test_kern_addr, 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(test_kern_addr, test_user_addr, size / 2)) { 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(test_kern_addr, test_user_addr, 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); } /* * This checks for the specific whitelist window within an object. If this * test passes, then do_usercopy_heap_size() tests will pass too. */ static void do_usercopy_heap_whitelist(bool to_user) { unsigned long user_alloc; unsigned char *buf = NULL; unsigned char __user *user_addr; size_t offset, size; /* Make sure cache was prepared. */ if (!whitelist_cache) { pr_warn("Failed to allocate kernel cache\n"); return; } /* * Allocate a buffer with a whitelisted window in the buffer. */ buf = kmem_cache_alloc(whitelist_cache, GFP_KERNEL); if (!buf) { pr_warn("Failed to allocate buffer from whitelist cache\n"); goto free_alloc; } /* Allocate user memory we'll poke at. */ user_alloc = vm_mmap(NULL, 0, PAGE_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC, MAP_ANONYMOUS | MAP_PRIVATE, 0); if (user_alloc >= TASK_SIZE) { pr_warn("Failed to allocate user memory\n"); goto free_alloc; } user_addr = (void __user *)user_alloc; memset(buf, 'B', cache_size); /* Whitelisted window in buffer, from kmem_cache_create_usercopy. */ offset = (cache_size / 4) + unconst; size = (cache_size / 16) + unconst; if (to_user) { pr_info("attempting good copy_to_user inside whitelist\n"); if (copy_to_user(user_addr, buf + offset, size)) { pr_warn("copy_to_user failed unexpectedly?!\n"); goto free_user; } pr_info("attempting bad copy_to_user outside whitelist\n"); if (copy_to_user(user_addr, buf + offset - 1, size)) { pr_warn("copy_to_user failed, but lacked Oops\n"); goto free_user; } } else { pr_info("attempting good copy_from_user inside whitelist\n"); if (copy_from_user(buf + offset, user_addr, size)) { pr_warn("copy_from_user failed unexpectedly?!\n"); goto free_user; } pr_info("attempting bad copy_from_user outside whitelist\n"); if (copy_from_user(buf + offset - 1, user_addr, size)) { pr_warn("copy_from_user failed, but lacked Oops\n"); goto free_user; } } free_user: vm_munmap(user_alloc, PAGE_SIZE); free_alloc: if (buf) kmem_cache_free(whitelist_cache, 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_WHITELIST_TO(void) { do_usercopy_heap_whitelist(true); } void lkdtm_USERCOPY_HEAP_WHITELIST_FROM(void) { do_usercopy_heap_whitelist(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, unconst + 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, vm_mmap, unconst + PAGE_SIZE)) { pr_warn("copy_to_user failed, but lacked Oops\n"); goto free_user; } free_user: vm_munmap(user_addr, PAGE_SIZE); } void lkdtm_USERCOPY_KERNEL_DS(void) { char __user *user_ptr = (char __user *)ERR_PTR(-EINVAL); mm_segment_t old_fs = get_fs(); char buf[10] = {0}; pr_info("attempting copy_to_user on unmapped kernel address\n"); set_fs(KERNEL_DS); if (copy_to_user(user_ptr, buf, sizeof(buf))) pr_info("copy_to_user un unmapped kernel address failed\n"); set_fs(old_fs); } void __init lkdtm_usercopy_init(void) { /* Prepare cache that lacks SLAB_USERCOPY flag. */ whitelist_cache = kmem_cache_create_usercopy("lkdtm-usercopy", cache_size, 0, 0, cache_size / 4, cache_size / 16, NULL); } void __exit lkdtm_usercopy_exit(void) { kmem_cache_destroy(whitelist_cache); }
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