458 lines
12 KiB
C
458 lines
12 KiB
C
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// SPDX-License-Identifier: GPL-2.0
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/*
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* This is for all the tests related to copy_to_user() and copy_from_user()
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* hardening.
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*/
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#include "lkdtm.h"
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#include <linux/slab.h>
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#include <linux/highmem.h>
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#include <linux/vmalloc.h>
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#include <linux/sched/task_stack.h>
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#include <linux/mman.h>
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#include <linux/uaccess.h>
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#include <asm/cacheflush.h>
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/*
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* Many of the tests here end up using const sizes, but those would
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* normally be ignored by hardened usercopy, so force the compiler
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* into choosing the non-const path to make sure we trigger the
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* hardened usercopy checks by added "unconst" to all the const copies,
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* and making sure "cache_size" isn't optimized into a const.
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*/
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static volatile size_t unconst;
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static volatile size_t cache_size = 1024;
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static struct kmem_cache *whitelist_cache;
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static const unsigned char test_text[] = "This is a test.\n";
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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 + unconst;
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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[128];
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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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/*
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* Put the target buffer in the middle of stack allocation
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* so that we don't step on future stack users regardless
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* of stack growth direction.
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*/
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return trick_compiler(&buf[(128/2)-32]);
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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((uintptr_t)&bad_stack);
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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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#ifdef ARCH_HAS_CURRENT_STACK_POINTER
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pr_info("stack : %px\n", (void *)current_stack_pointer);
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#endif
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pr_info("good_stack: %px-%px\n", good_stack, good_stack + sizeof(good_stack));
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pr_info("bad_stack : %px-%px\n", bad_stack, bad_stack + sizeof(good_stack));
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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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unconst + 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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unconst + 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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unconst + 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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unconst + 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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/*
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* This checks for whole-object size validation with hardened usercopy,
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* with or without usercopy whitelisting.
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*/
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static void do_usercopy_slab_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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void __user *test_user_addr;
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void *test_kern_addr;
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size_t size = unconst + 1024;
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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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test_user_addr = (void __user *)(user_addr + 16);
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test_kern_addr = one + 16;
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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(test_user_addr, test_kern_addr, size / 2)) {
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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(test_user_addr, test_kern_addr, 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(test_kern_addr, test_user_addr, size / 2)) {
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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(test_kern_addr, test_user_addr, 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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pr_err("FAIL: bad usercopy not detected!\n");
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pr_expected_config_param(CONFIG_HARDENED_USERCOPY, "hardened_usercopy");
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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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/*
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* This checks for the specific whitelist window within an object. If this
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* test passes, then do_usercopy_slab_size() tests will pass too.
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*/
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static void do_usercopy_slab_whitelist(bool to_user)
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{
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unsigned long user_alloc;
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unsigned char *buf = NULL;
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unsigned char __user *user_addr;
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size_t offset, size;
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/* Make sure cache was prepared. */
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if (!whitelist_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 a buffer with a whitelisted window in the buffer.
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*/
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buf = kmem_cache_alloc(whitelist_cache, GFP_KERNEL);
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if (!buf) {
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pr_warn("Failed to allocate buffer from whitelist cache\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_alloc = 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_alloc >= 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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user_addr = (void __user *)user_alloc;
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memset(buf, 'B', cache_size);
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/* Whitelisted window in buffer, from kmem_cache_create_usercopy. */
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offset = (cache_size / 4) + unconst;
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size = (cache_size / 16) + unconst;
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if (to_user) {
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pr_info("attempting good copy_to_user inside whitelist\n");
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if (copy_to_user(user_addr, buf + offset, 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 outside whitelist\n");
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if (copy_to_user(user_addr, buf + offset - 1, 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 inside whitelist\n");
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if (copy_from_user(buf + offset, user_addr, 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 outside whitelist\n");
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if (copy_from_user(buf + offset - 1, user_addr, 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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pr_err("FAIL: bad usercopy not detected!\n");
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pr_expected_config_param(CONFIG_HARDENED_USERCOPY, "hardened_usercopy");
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free_user:
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vm_munmap(user_alloc, PAGE_SIZE);
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free_alloc:
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if (buf)
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kmem_cache_free(whitelist_cache, buf);
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}
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/* Callable tests. */
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static void lkdtm_USERCOPY_SLAB_SIZE_TO(void)
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{
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do_usercopy_slab_size(true);
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}
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static void lkdtm_USERCOPY_SLAB_SIZE_FROM(void)
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{
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do_usercopy_slab_size(false);
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}
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static void lkdtm_USERCOPY_SLAB_WHITELIST_TO(void)
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{
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do_usercopy_slab_whitelist(true);
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}
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static void lkdtm_USERCOPY_SLAB_WHITELIST_FROM(void)
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{
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do_usercopy_slab_whitelist(false);
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}
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static void lkdtm_USERCOPY_STACK_FRAME_TO(void)
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{
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do_usercopy_stack(true, true);
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}
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static void lkdtm_USERCOPY_STACK_FRAME_FROM(void)
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{
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do_usercopy_stack(false, true);
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}
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static void lkdtm_USERCOPY_STACK_BEYOND(void)
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{
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do_usercopy_stack(true, false);
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}
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static void lkdtm_USERCOPY_KERNEL(void)
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{
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unsigned long user_addr;
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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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pr_info("attempting good copy_to_user from kernel rodata: %px\n",
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test_text);
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if (copy_to_user((void __user *)user_addr, test_text,
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unconst + sizeof(test_text))) {
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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 from kernel text: %px\n",
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vm_mmap);
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if (copy_to_user((void __user *)user_addr, vm_mmap,
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unconst + PAGE_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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pr_err("FAIL: bad copy_to_user() not detected!\n");
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pr_expected_config_param(CONFIG_HARDENED_USERCOPY, "hardened_usercopy");
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free_user:
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vm_munmap(user_addr, PAGE_SIZE);
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}
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/*
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* This expects "kaddr" to point to a PAGE_SIZE allocation, which means
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* a more complete test that would include copy_from_user() would risk
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* memory corruption. Just test copy_to_user() here, as that exercises
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* almost exactly the same code paths.
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*/
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static void do_usercopy_page_span(const char *name, void *kaddr)
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{
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unsigned long uaddr;
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uaddr = vm_mmap(NULL, 0, PAGE_SIZE, PROT_READ | PROT_WRITE,
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MAP_ANONYMOUS | MAP_PRIVATE, 0);
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if (uaddr >= 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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/* Initialize contents. */
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memset(kaddr, 0xAA, PAGE_SIZE);
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/* Bump the kaddr forward to detect a page-spanning overflow. */
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|
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kaddr += PAGE_SIZE / 2;
|
||
|
|
|
||
|
|
pr_info("attempting good copy_to_user() from kernel %s: %px\n",
|
||
|
|
name, kaddr);
|
||
|
|
if (copy_to_user((void __user *)uaddr, kaddr,
|
||
|
|
unconst + (PAGE_SIZE / 2))) {
|
||
|
|
pr_err("copy_to_user() failed unexpectedly?!\n");
|
||
|
|
goto free_user;
|
||
|
|
}
|
||
|
|
|
||
|
|
pr_info("attempting bad copy_to_user() from kernel %s: %px\n",
|
||
|
|
name, kaddr);
|
||
|
|
if (copy_to_user((void __user *)uaddr, kaddr, unconst + PAGE_SIZE)) {
|
||
|
|
pr_warn("Good, copy_to_user() failed, but lacked Oops(?!)\n");
|
||
|
|
goto free_user;
|
||
|
|
}
|
||
|
|
|
||
|
|
pr_err("FAIL: bad copy_to_user() not detected!\n");
|
||
|
|
pr_expected_config_param(CONFIG_HARDENED_USERCOPY, "hardened_usercopy");
|
||
|
|
|
||
|
|
free_user:
|
||
|
|
vm_munmap(uaddr, PAGE_SIZE);
|
||
|
|
}
|
||
|
|
|
||
|
|
static void lkdtm_USERCOPY_VMALLOC(void)
|
||
|
|
{
|
||
|
|
void *addr;
|
||
|
|
|
||
|
|
addr = vmalloc(PAGE_SIZE);
|
||
|
|
if (!addr) {
|
||
|
|
pr_err("vmalloc() failed!?\n");
|
||
|
|
return;
|
||
|
|
}
|
||
|
|
do_usercopy_page_span("vmalloc", addr);
|
||
|
|
vfree(addr);
|
||
|
|
}
|
||
|
|
|
||
|
|
static void lkdtm_USERCOPY_FOLIO(void)
|
||
|
|
{
|
||
|
|
struct folio *folio;
|
||
|
|
void *addr;
|
||
|
|
|
||
|
|
/*
|
||
|
|
* FIXME: Folio checking currently misses 0-order allocations, so
|
||
|
|
* allocate and bump forward to the last page.
|
||
|
|
*/
|
||
|
|
folio = folio_alloc(GFP_KERNEL | __GFP_ZERO, 1);
|
||
|
|
if (!folio) {
|
||
|
|
pr_err("folio_alloc() failed!?\n");
|
||
|
|
return;
|
||
|
|
}
|
||
|
|
addr = folio_address(folio);
|
||
|
|
if (addr)
|
||
|
|
do_usercopy_page_span("folio", addr + PAGE_SIZE);
|
||
|
|
else
|
||
|
|
pr_err("folio_address() failed?!\n");
|
||
|
|
folio_put(folio);
|
||
|
|
}
|
||
|
|
|
||
|
|
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);
|
||
|
|
}
|
||
|
|
|
||
|
|
static struct crashtype crashtypes[] = {
|
||
|
|
CRASHTYPE(USERCOPY_SLAB_SIZE_TO),
|
||
|
|
CRASHTYPE(USERCOPY_SLAB_SIZE_FROM),
|
||
|
|
CRASHTYPE(USERCOPY_SLAB_WHITELIST_TO),
|
||
|
|
CRASHTYPE(USERCOPY_SLAB_WHITELIST_FROM),
|
||
|
|
CRASHTYPE(USERCOPY_STACK_FRAME_TO),
|
||
|
|
CRASHTYPE(USERCOPY_STACK_FRAME_FROM),
|
||
|
|
CRASHTYPE(USERCOPY_STACK_BEYOND),
|
||
|
|
CRASHTYPE(USERCOPY_VMALLOC),
|
||
|
|
CRASHTYPE(USERCOPY_FOLIO),
|
||
|
|
CRASHTYPE(USERCOPY_KERNEL),
|
||
|
|
};
|
||
|
|
|
||
|
|
struct crashtype_category usercopy_crashtypes = {
|
||
|
|
.crashtypes = crashtypes,
|
||
|
|
.len = ARRAY_SIZE(crashtypes),
|
||
|
|
};
|