The testing module triggers KMSAN warnings in different cases and checks that the errors are properly reported, using console probes to capture the tool's output. Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx> --- v2: -- add memcpy tests Link: https://linux-review.googlesource.com/id/I49c3f59014cc37fd13541c80beb0b75a75244650 --- lib/Kconfig.kmsan | 16 ++ mm/kmsan/Makefile | 4 + mm/kmsan/kmsan_test.c | 536 ++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 556 insertions(+) create mode 100644 mm/kmsan/kmsan_test.c diff --git a/lib/Kconfig.kmsan b/lib/Kconfig.kmsan index 199f79d031f94..a68fdb5ed5d92 100644 --- a/lib/Kconfig.kmsan +++ b/lib/Kconfig.kmsan @@ -21,3 +21,19 @@ config KMSAN the whole system down. See <file:Documentation/dev-tools/kmsan.rst> for more details. + +if KMSAN + +config KMSAN_KUNIT_TEST + tristate "KMSAN integration test suite" if !KUNIT_ALL_TESTS + default KUNIT_ALL_TESTS + depends on TRACEPOINTS && KUNIT + help + Test suite for KMSAN, testing various error detection scenarios, + and checking that reports are correctly output to console. + + Say Y here if you want the test to be built into the kernel and run + during boot; say M if you want the test to build as a module; say N + if you are unsure. + +endif diff --git a/mm/kmsan/Makefile b/mm/kmsan/Makefile index f57a956cb1c8b..7be6a7e92394f 100644 --- a/mm/kmsan/Makefile +++ b/mm/kmsan/Makefile @@ -20,3 +20,7 @@ CFLAGS_init.o := $(CC_FLAGS_KMSAN_RUNTIME) CFLAGS_instrumentation.o := $(CC_FLAGS_KMSAN_RUNTIME) CFLAGS_report.o := $(CC_FLAGS_KMSAN_RUNTIME) CFLAGS_shadow.o := $(CC_FLAGS_KMSAN_RUNTIME) + +obj-$(CONFIG_KMSAN_KUNIT_TEST) += kmsan_test.o +KMSAN_SANITIZE_kmsan_test.o := y +CFLAGS_kmsan_test.o += $(call cc-disable-warning, uninitialized) diff --git a/mm/kmsan/kmsan_test.c b/mm/kmsan/kmsan_test.c new file mode 100644 index 0000000000000..44bb2e0f87d81 --- /dev/null +++ b/mm/kmsan/kmsan_test.c @@ -0,0 +1,536 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Test cases for KMSAN. + * For each test case checks the presence (or absence) of generated reports. + * Relies on 'console' tracepoint to capture reports as they appear in the + * kernel log. + * + * Copyright (C) 2021-2022, Google LLC. + * Author: Alexander Potapenko <glider@xxxxxxxxxx> + * + */ + +#include <kunit/test.h> +#include "kmsan.h" + +#include <linux/jiffies.h> +#include <linux/kernel.h> +#include <linux/kmsan.h> +#include <linux/mm.h> +#include <linux/random.h> +#include <linux/slab.h> +#include <linux/spinlock.h> +#include <linux/string.h> +#include <linux/tracepoint.h> +#include <trace/events/printk.h> + +static DEFINE_PER_CPU(int, per_cpu_var); + +/* Report as observed from console. */ +static struct { + spinlock_t lock; + bool available; + bool ignore; /* Stop console output collection. */ + char header[256]; +} observed = { + .lock = __SPIN_LOCK_UNLOCKED(observed.lock), +}; + +/* Probe for console output: obtains observed lines of interest. */ +static void probe_console(void *ignore, const char *buf, size_t len) +{ + unsigned long flags; + + if (observed.ignore) + return; + spin_lock_irqsave(&observed.lock, flags); + + if (strnstr(buf, "BUG: KMSAN: ", len)) { + /* + * KMSAN report and related to the test. + * + * The provided @buf is not NUL-terminated; copy no more than + * @len bytes and let strscpy() add the missing NUL-terminator. + */ + strscpy(observed.header, buf, + min(len + 1, sizeof(observed.header))); + WRITE_ONCE(observed.available, true); + observed.ignore = true; + } + spin_unlock_irqrestore(&observed.lock, flags); +} + +/* Check if a report related to the test exists. */ +static bool report_available(void) +{ + return READ_ONCE(observed.available); +} + +/* Information we expect in a report. */ +struct expect_report { + const char *error_type; /* Error type. */ + /* + * Kernel symbol from the error header, or NULL if no report is + * expected. + */ + const char *symbol; +}; + +/* Check observed report matches information in @r. */ +static bool report_matches(const struct expect_report *r) +{ + typeof(observed.header) expected_header; + unsigned long flags; + bool ret = false; + const char *end; + char *cur; + + /* Doubled-checked locking. */ + if (!report_available() || !r->symbol) + return (!report_available() && !r->symbol); + + /* Generate expected report contents. */ + + /* Title */ + cur = expected_header; + end = &expected_header[sizeof(expected_header) - 1]; + + cur += scnprintf(cur, end - cur, "BUG: KMSAN: %s", r->error_type); + + scnprintf(cur, end - cur, " in %s", r->symbol); + /* The exact offset won't match, remove it; also strip module name. */ + cur = strchr(expected_header, '+'); + if (cur) + *cur = '\0'; + + spin_lock_irqsave(&observed.lock, flags); + if (!report_available()) + goto out; /* A new report is being captured. */ + + /* Finally match expected output to what we actually observed. */ + ret = strstr(observed.header, expected_header); +out: + spin_unlock_irqrestore(&observed.lock, flags); + + return ret; +} + +/* ===== Test cases ===== */ + +/* Prevent replacing branch with select in LLVM. */ +static noinline void check_true(char *arg) +{ + pr_info("%s is true\n", arg); +} + +static noinline void check_false(char *arg) +{ + pr_info("%s is false\n", arg); +} + +#define USE(x) \ + do { \ + if (x) \ + check_true(#x); \ + else \ + check_false(#x); \ + } while (0) + +#define EXPECTATION_ETYPE_FN(e, reason, fn) \ + struct expect_report e = { \ + .error_type = reason, \ + .symbol = fn, \ + } + +#define EXPECTATION_NO_REPORT(e) EXPECTATION_ETYPE_FN(e, NULL, NULL) +#define EXPECTATION_UNINIT_VALUE_FN(e, fn) \ + EXPECTATION_ETYPE_FN(e, "uninit-value", fn) +#define EXPECTATION_UNINIT_VALUE(e) EXPECTATION_UNINIT_VALUE_FN(e, __func__) +#define EXPECTATION_USE_AFTER_FREE(e) \ + EXPECTATION_ETYPE_FN(e, "use-after-free", __func__) + +/* Test case: ensure that kmalloc() returns uninitialized memory. */ +static void test_uninit_kmalloc(struct kunit *test) +{ + EXPECTATION_UNINIT_VALUE(expect); + int *ptr; + + kunit_info(test, "uninitialized kmalloc test (UMR report)\n"); + ptr = kmalloc(sizeof(int), GFP_KERNEL); + USE(*ptr); + KUNIT_EXPECT_TRUE(test, report_matches(&expect)); +} + +/* + * Test case: ensure that kmalloc'ed memory becomes initialized after memset(). + */ +static void test_init_kmalloc(struct kunit *test) +{ + EXPECTATION_NO_REPORT(expect); + int *ptr; + + kunit_info(test, "initialized kmalloc test (no reports)\n"); + ptr = kmalloc(sizeof(int), GFP_KERNEL); + memset(ptr, 0, sizeof(int)); + USE(*ptr); + KUNIT_EXPECT_TRUE(test, report_matches(&expect)); +} + +/* Test case: ensure that kzalloc() returns initialized memory. */ +static void test_init_kzalloc(struct kunit *test) +{ + EXPECTATION_NO_REPORT(expect); + int *ptr; + + kunit_info(test, "initialized kzalloc test (no reports)\n"); + ptr = kzalloc(sizeof(int), GFP_KERNEL); + USE(*ptr); + KUNIT_EXPECT_TRUE(test, report_matches(&expect)); +} + +/* Test case: ensure that local variables are uninitialized by default. */ +static void test_uninit_stack_var(struct kunit *test) +{ + EXPECTATION_UNINIT_VALUE(expect); + volatile int cond; + + kunit_info(test, "uninitialized stack variable (UMR report)\n"); + USE(cond); + KUNIT_EXPECT_TRUE(test, report_matches(&expect)); +} + +/* Test case: ensure that local variables with initializers are initialized. */ +static void test_init_stack_var(struct kunit *test) +{ + EXPECTATION_NO_REPORT(expect); + volatile int cond = 1; + + kunit_info(test, "initialized stack variable (no reports)\n"); + USE(cond); + KUNIT_EXPECT_TRUE(test, report_matches(&expect)); +} + +static noinline void two_param_fn_2(int arg1, int arg2) +{ + USE(arg1); + USE(arg2); +} + +static noinline void one_param_fn(int arg) +{ + two_param_fn_2(arg, arg); + USE(arg); +} + +static noinline void two_param_fn(int arg1, int arg2) +{ + int init = 0; + + one_param_fn(init); + USE(arg1); + USE(arg2); +} + +static void test_params(struct kunit *test) +{ + EXPECTATION_UNINIT_VALUE_FN(expect, "two_param_fn"); + volatile int uninit, init = 1; + + kunit_info(test, + "uninit passed through a function parameter (UMR report)\n"); + two_param_fn(uninit, init); + KUNIT_EXPECT_TRUE(test, report_matches(&expect)); +} + +static int signed_sum3(int a, int b, int c) +{ + return a + b + c; +} + +/* + * Test case: ensure that uninitialized values are tracked through function + * arguments. + */ +static void test_uninit_multiple_params(struct kunit *test) +{ + EXPECTATION_UNINIT_VALUE(expect); + volatile char b = 3, c; + volatile int a; + + kunit_info(test, "uninitialized local passed to fn (UMR report)\n"); + USE(signed_sum3(a, b, c)); + KUNIT_EXPECT_TRUE(test, report_matches(&expect)); +} + +/* Helper function to make an array uninitialized. */ +static noinline void do_uninit_local_array(char *array, int start, int stop) +{ + volatile char uninit; + int i; + + for (i = start; i < stop; i++) + array[i] = uninit; +} + +/* + * Test case: ensure kmsan_check_memory() reports an error when checking + * uninitialized memory. + */ +static void test_uninit_kmsan_check_memory(struct kunit *test) +{ + EXPECTATION_UNINIT_VALUE_FN(expect, "test_uninit_kmsan_check_memory"); + volatile char local_array[8]; + + kunit_info( + test, + "kmsan_check_memory() called on uninit local (UMR report)\n"); + do_uninit_local_array((char *)local_array, 5, 7); + + kmsan_check_memory((char *)local_array, 8); + KUNIT_EXPECT_TRUE(test, report_matches(&expect)); +} + +/* + * Test case: check that a virtual memory range created with vmap() from + * initialized pages is still considered as initialized. + */ +static void test_init_kmsan_vmap_vunmap(struct kunit *test) +{ + EXPECTATION_NO_REPORT(expect); + const int npages = 2; + struct page **pages; + void *vbuf; + int i; + + kunit_info(test, "pages initialized via vmap (no reports)\n"); + + pages = kmalloc_array(npages, sizeof(struct page), GFP_KERNEL); + for (i = 0; i < npages; i++) + pages[i] = alloc_page(GFP_KERNEL); + vbuf = vmap(pages, npages, VM_MAP, PAGE_KERNEL); + memset(vbuf, 0xfe, npages * PAGE_SIZE); + for (i = 0; i < npages; i++) + kmsan_check_memory(page_address(pages[i]), PAGE_SIZE); + + if (vbuf) + vunmap(vbuf); + for (i = 0; i < npages; i++) + if (pages[i]) + __free_page(pages[i]); + kfree(pages); + KUNIT_EXPECT_TRUE(test, report_matches(&expect)); +} + +/* + * Test case: ensure that memset() can initialize a buffer allocated via + * vmalloc(). + */ +static void test_init_vmalloc(struct kunit *test) +{ + EXPECTATION_NO_REPORT(expect); + int npages = 8, i; + char *buf; + + kunit_info(test, "vmalloc buffer can be initialized (no reports)\n"); + buf = vmalloc(PAGE_SIZE * npages); + buf[0] = 1; + memset(buf, 0xfe, PAGE_SIZE * npages); + USE(buf[0]); + for (i = 0; i < npages; i++) + kmsan_check_memory(&buf[PAGE_SIZE * i], PAGE_SIZE); + vfree(buf); + KUNIT_EXPECT_TRUE(test, report_matches(&expect)); +} + +/* Test case: ensure that use-after-free reporting works. */ +static void test_uaf(struct kunit *test) +{ + EXPECTATION_USE_AFTER_FREE(expect); + volatile int value; + volatile int *var; + + kunit_info(test, "use-after-free in kmalloc-ed buffer (UMR report)\n"); + var = kmalloc(80, GFP_KERNEL); + var[3] = 0xfeedface; + kfree((int *)var); + /* Copy the invalid value before checking it. */ + value = var[3]; + USE(value); + KUNIT_EXPECT_TRUE(test, report_matches(&expect)); +} + +/* + * Test case: ensure that uninitialized values are propagated through per-CPU + * memory. + */ +static void test_percpu_propagate(struct kunit *test) +{ + EXPECTATION_UNINIT_VALUE(expect); + volatile int uninit, check; + + kunit_info(test, + "uninit local stored to per_cpu memory (UMR report)\n"); + + this_cpu_write(per_cpu_var, uninit); + check = this_cpu_read(per_cpu_var); + USE(check); + KUNIT_EXPECT_TRUE(test, report_matches(&expect)); +} + +/* + * Test case: ensure that passing uninitialized values to printk() leads to an + * error report. + */ +static void test_printk(struct kunit *test) +{ + EXPECTATION_UNINIT_VALUE_FN(expect, "number"); + volatile int uninit; + + kunit_info(test, "uninit local passed to pr_info() (UMR report)\n"); + pr_info("%px contains %d\n", &uninit, uninit); + KUNIT_EXPECT_TRUE(test, report_matches(&expect)); +} + +/* + * Test case: ensure that memcpy() correctly copies uninitialized values between + * aligned `src` and `dst`. + */ +static void test_memcpy_aligned_to_aligned(struct kunit *test) +{ + EXPECTATION_UNINIT_VALUE_FN(expect, "test_memcpy_aligned_to_aligned"); + volatile int uninit_src; + volatile int dst = 0; + + kunit_info(test, "memcpy()ing aligned uninit src to aligned dst (UMR report)\n"); + memcpy((void *)&dst, (void *)&uninit_src, sizeof(uninit_src)); + kmsan_check_memory((void *)&dst, sizeof(dst)); + KUNIT_EXPECT_TRUE(test, report_matches(&expect)); +} + +/* + * Test case: ensure that memcpy() correctly copies uninitialized values between + * aligned `src` and unaligned `dst`. + * + * Copying aligned 4-byte value to an unaligned one leads to touching two + * aligned 4-byte values. This test case checks that KMSAN correctly reports an + * error on the first of the two values. + */ +static void test_memcpy_aligned_to_unaligned(struct kunit *test) +{ + EXPECTATION_UNINIT_VALUE_FN(expect, "test_memcpy_aligned_to_unaligned"); + volatile int uninit_src; + volatile char dst[8] = {0}; + + kunit_info(test, "memcpy()ing aligned uninit src to unaligned dst (UMR report)\n"); + memcpy((void *)&dst[1], (void *)&uninit_src, sizeof(uninit_src)); + kmsan_check_memory((void *)dst, 4); + KUNIT_EXPECT_TRUE(test, report_matches(&expect)); +} + +/* + * Test case: ensure that memcpy() correctly copies uninitialized values between + * aligned `src` and unaligned `dst`. + * + * Copying aligned 4-byte value to an unaligned one leads to touching two + * aligned 4-byte values. This test case checks that KMSAN correctly reports an + * error on the second of the two values. + */ +static void test_memcpy_aligned_to_unaligned2(struct kunit *test) +{ + EXPECTATION_UNINIT_VALUE_FN(expect, "test_memcpy_aligned_to_unaligned2"); + volatile int uninit_src; + volatile char dst[8] = {0}; + + kunit_info(test, "memcpy()ing aligned uninit src to unaligned dst - part 2 (UMR report)\n"); + memcpy((void *)&dst[1], (void *)&uninit_src, sizeof(uninit_src)); + kmsan_check_memory((void *)&dst[4], sizeof(uninit_src)); + KUNIT_EXPECT_TRUE(test, report_matches(&expect)); +} + +static struct kunit_case kmsan_test_cases[] = { + KUNIT_CASE(test_uninit_kmalloc), + KUNIT_CASE(test_init_kmalloc), + KUNIT_CASE(test_init_kzalloc), + KUNIT_CASE(test_uninit_stack_var), + KUNIT_CASE(test_init_stack_var), + KUNIT_CASE(test_params), + KUNIT_CASE(test_uninit_multiple_params), + KUNIT_CASE(test_uninit_kmsan_check_memory), + KUNIT_CASE(test_init_kmsan_vmap_vunmap), + KUNIT_CASE(test_init_vmalloc), + KUNIT_CASE(test_uaf), + KUNIT_CASE(test_percpu_propagate), + KUNIT_CASE(test_printk), + KUNIT_CASE(test_memcpy_aligned_to_aligned), + KUNIT_CASE(test_memcpy_aligned_to_unaligned), + KUNIT_CASE(test_memcpy_aligned_to_unaligned2), + {}, +}; + +/* ===== End test cases ===== */ + +static int test_init(struct kunit *test) +{ + unsigned long flags; + + spin_lock_irqsave(&observed.lock, flags); + observed.header[0] = '\0'; + observed.ignore = false; + observed.available = false; + spin_unlock_irqrestore(&observed.lock, flags); + + return 0; +} + +static void test_exit(struct kunit *test) +{ +} + +static struct kunit_suite kmsan_test_suite = { + .name = "kmsan", + .test_cases = kmsan_test_cases, + .init = test_init, + .exit = test_exit, +}; +static struct kunit_suite *kmsan_test_suites[] = { &kmsan_test_suite, NULL }; + +static void register_tracepoints(struct tracepoint *tp, void *ignore) +{ + check_trace_callback_type_console(probe_console); + if (!strcmp(tp->name, "console")) + WARN_ON(tracepoint_probe_register(tp, probe_console, NULL)); +} + +static void unregister_tracepoints(struct tracepoint *tp, void *ignore) +{ + if (!strcmp(tp->name, "console")) + tracepoint_probe_unregister(tp, probe_console, NULL); +} + +/* + * We only want to do tracepoints setup and teardown once, therefore we have to + * customize the init and exit functions and cannot rely on kunit_test_suite(). + */ +static int __init kmsan_test_init(void) +{ + /* + * Because we want to be able to build the test as a module, we need to + * iterate through all known tracepoints, since the static registration + * won't work here. + */ + for_each_kernel_tracepoint(register_tracepoints, NULL); + return __kunit_test_suites_init(kmsan_test_suites); +} + +static void kmsan_test_exit(void) +{ + __kunit_test_suites_exit(kmsan_test_suites); + for_each_kernel_tracepoint(unregister_tracepoints, NULL); + tracepoint_synchronize_unregister(); +} + +late_initcall_sync(kmsan_test_init); +module_exit(kmsan_test_exit); + +MODULE_LICENSE("GPL v2"); +MODULE_AUTHOR("Alexander Potapenko <glider@xxxxxxxxxx>"); -- 2.35.1.1021.g381101b075-goog
