diff options
Diffstat (limited to 'drivers/misc/lkdtm/usercopy.c')
| -rw-r--r-- | drivers/misc/lkdtm/usercopy.c | 146 |
1 files changed, 128 insertions, 18 deletions
diff --git a/drivers/misc/lkdtm/usercopy.c b/drivers/misc/lkdtm/usercopy.c index 9161ce7ed47a..6215ec995cd3 100644 --- a/drivers/misc/lkdtm/usercopy.c +++ b/drivers/misc/lkdtm/usercopy.c @@ -5,6 +5,7 @@ */ #include "lkdtm.h" #include <linux/slab.h> +#include <linux/highmem.h> #include <linux/vmalloc.h> #include <linux/sched/task_stack.h> #include <linux/mman.h> @@ -30,12 +31,12 @@ static const unsigned char test_text[] = "This is a test.\n"; */ static noinline unsigned char *trick_compiler(unsigned char *stack) { - return stack + 0; + return stack + unconst; } static noinline unsigned char *do_usercopy_stack_callee(int value) { - unsigned char buf[32]; + unsigned char buf[128]; int i; /* Exercise stack to avoid everything living in registers. */ @@ -43,7 +44,12 @@ static noinline unsigned char *do_usercopy_stack_callee(int value) buf[i] = value & 0xff; } - return trick_compiler(buf); + /* + * Put the target buffer in the middle of stack allocation + * so that we don't step on future stack users regardless + * of stack growth direction. + */ + return trick_compiler(&buf[(128/2)-32]); } static noinline void do_usercopy_stack(bool to_user, bool bad_frame) @@ -66,6 +72,12 @@ static noinline void do_usercopy_stack(bool to_user, bool bad_frame) bad_stack -= sizeof(unsigned long); } +#ifdef ARCH_HAS_CURRENT_STACK_POINTER + pr_info("stack : %px\n", (void *)current_stack_pointer); +#endif + pr_info("good_stack: %px-%px\n", good_stack, good_stack + sizeof(good_stack)); + pr_info("bad_stack : %px-%px\n", bad_stack, bad_stack + sizeof(good_stack)); + user_addr = vm_mmap(NULL, 0, PAGE_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC, MAP_ANONYMOUS | MAP_PRIVATE, 0); @@ -119,7 +131,7 @@ free_user: * This checks for whole-object size validation with hardened usercopy, * with or without usercopy whitelisting. */ -static void do_usercopy_heap_size(bool to_user) +static void do_usercopy_slab_size(bool to_user) { unsigned long user_addr; unsigned char *one, *two; @@ -185,9 +197,9 @@ free_kernel: /* * This checks for the specific whitelist window within an object. If this - * test passes, then do_usercopy_heap_size() tests will pass too. + * test passes, then do_usercopy_slab_size() tests will pass too. */ -static void do_usercopy_heap_whitelist(bool to_user) +static void do_usercopy_slab_whitelist(bool to_user) { unsigned long user_alloc; unsigned char *buf = NULL; @@ -261,42 +273,42 @@ free_alloc: } /* Callable tests. */ -void lkdtm_USERCOPY_HEAP_SIZE_TO(void) +static void lkdtm_USERCOPY_SLAB_SIZE_TO(void) { - do_usercopy_heap_size(true); + do_usercopy_slab_size(true); } -void lkdtm_USERCOPY_HEAP_SIZE_FROM(void) +static void lkdtm_USERCOPY_SLAB_SIZE_FROM(void) { - do_usercopy_heap_size(false); + do_usercopy_slab_size(false); } -void lkdtm_USERCOPY_HEAP_WHITELIST_TO(void) +static void lkdtm_USERCOPY_SLAB_WHITELIST_TO(void) { - do_usercopy_heap_whitelist(true); + do_usercopy_slab_whitelist(true); } -void lkdtm_USERCOPY_HEAP_WHITELIST_FROM(void) +static void lkdtm_USERCOPY_SLAB_WHITELIST_FROM(void) { - do_usercopy_heap_whitelist(false); + do_usercopy_slab_whitelist(false); } -void lkdtm_USERCOPY_STACK_FRAME_TO(void) +static void lkdtm_USERCOPY_STACK_FRAME_TO(void) { do_usercopy_stack(true, true); } -void lkdtm_USERCOPY_STACK_FRAME_FROM(void) +static void lkdtm_USERCOPY_STACK_FRAME_FROM(void) { do_usercopy_stack(false, true); } -void lkdtm_USERCOPY_STACK_BEYOND(void) +static void lkdtm_USERCOPY_STACK_BEYOND(void) { do_usercopy_stack(true, false); } -void lkdtm_USERCOPY_KERNEL(void) +static void lkdtm_USERCOPY_KERNEL(void) { unsigned long user_addr; @@ -330,6 +342,86 @@ free_user: vm_munmap(user_addr, PAGE_SIZE); } +/* + * This expects "kaddr" to point to a PAGE_SIZE allocation, which means + * a more complete test that would include copy_from_user() would risk + * memory corruption. Just test copy_to_user() here, as that exercises + * almost exactly the same code paths. + */ +static void do_usercopy_page_span(const char *name, void *kaddr) +{ + unsigned long uaddr; + + uaddr = vm_mmap(NULL, 0, PAGE_SIZE, PROT_READ | PROT_WRITE, + MAP_ANONYMOUS | MAP_PRIVATE, 0); + if (uaddr >= TASK_SIZE) { + pr_warn("Failed to allocate user memory\n"); + return; + } + + /* Initialize contents. */ + memset(kaddr, 0xAA, PAGE_SIZE); + + /* Bump the kaddr forward to detect a page-spanning overflow. */ + 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. */ @@ -345,3 +437,21 @@ 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), +}; |