diff options
| -rw-r--r-- | Makefile | 1 | ||||
| -rw-r--r-- | include/linux/kmsan-checks.h | 64 | ||||
| -rw-r--r-- | include/linux/kmsan_types.h | 35 | ||||
| -rw-r--r-- | include/linux/mm_types.h | 12 | ||||
| -rw-r--r-- | include/linux/sched.h | 5 | ||||
| -rw-r--r-- | lib/Kconfig.debug | 1 | ||||
| -rw-r--r-- | lib/Kconfig.kmsan | 50 | ||||
| -rw-r--r-- | mm/Makefile | 1 | ||||
| -rw-r--r-- | mm/kmsan/Makefile | 23 | ||||
| -rw-r--r-- | mm/kmsan/core.c | 440 | ||||
| -rw-r--r-- | mm/kmsan/hooks.c | 66 | ||||
| -rw-r--r-- | mm/kmsan/instrumentation.c | 307 | ||||
| -rw-r--r-- | mm/kmsan/kmsan.h | 204 | ||||
| -rw-r--r-- | mm/kmsan/report.c | 219 | ||||
| -rw-r--r-- | mm/kmsan/shadow.c | 147 | ||||
| -rw-r--r-- | scripts/Makefile.kmsan | 8 | ||||
| -rw-r--r-- | scripts/Makefile.lib | 9 |
17 files changed, 1592 insertions, 0 deletions
@@ -1015,6 +1015,7 @@ include-y := scripts/Makefile.extrawarn include-$(CONFIG_DEBUG_INFO) += scripts/Makefile.debug include-$(CONFIG_KASAN) += scripts/Makefile.kasan include-$(CONFIG_KCSAN) += scripts/Makefile.kcsan +include-$(CONFIG_KMSAN) += scripts/Makefile.kmsan include-$(CONFIG_UBSAN) += scripts/Makefile.ubsan include-$(CONFIG_KCOV) += scripts/Makefile.kcov include-$(CONFIG_RANDSTRUCT) += scripts/Makefile.randstruct diff --git a/include/linux/kmsan-checks.h b/include/linux/kmsan-checks.h new file mode 100644 index 000000000000..a6522a0c28df --- /dev/null +++ b/include/linux/kmsan-checks.h @@ -0,0 +1,64 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * KMSAN checks to be used for one-off annotations in subsystems. + * + * Copyright (C) 2017-2022 Google LLC + * Author: Alexander Potapenko <glider@google.com> + * + */ + +#ifndef _LINUX_KMSAN_CHECKS_H +#define _LINUX_KMSAN_CHECKS_H + +#include <linux/types.h> + +#ifdef CONFIG_KMSAN + +/** + * kmsan_poison_memory() - Mark the memory range as uninitialized. + * @address: address to start with. + * @size: size of buffer to poison. + * @flags: GFP flags for allocations done by this function. + * + * Until other data is written to this range, KMSAN will treat it as + * uninitialized. Error reports for this memory will reference the call site of + * kmsan_poison_memory() as origin. + */ +void kmsan_poison_memory(const void *address, size_t size, gfp_t flags); + +/** + * kmsan_unpoison_memory() - Mark the memory range as initialized. + * @address: address to start with. + * @size: size of buffer to unpoison. + * + * Until other data is written to this range, KMSAN will treat it as + * initialized. + */ +void kmsan_unpoison_memory(const void *address, size_t size); + +/** + * kmsan_check_memory() - Check the memory range for being initialized. + * @address: address to start with. + * @size: size of buffer to check. + * + * If any piece of the given range is marked as uninitialized, KMSAN will report + * an error. + */ +void kmsan_check_memory(const void *address, size_t size); + +#else + +static inline void kmsan_poison_memory(const void *address, size_t size, + gfp_t flags) +{ +} +static inline void kmsan_unpoison_memory(const void *address, size_t size) +{ +} +static inline void kmsan_check_memory(const void *address, size_t size) +{ +} + +#endif + +#endif /* _LINUX_KMSAN_CHECKS_H */ diff --git a/include/linux/kmsan_types.h b/include/linux/kmsan_types.h new file mode 100644 index 000000000000..8bfa6c98176d --- /dev/null +++ b/include/linux/kmsan_types.h @@ -0,0 +1,35 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * A minimal header declaring types added by KMSAN to existing kernel structs. + * + * Copyright (C) 2017-2022 Google LLC + * Author: Alexander Potapenko <glider@google.com> + * + */ +#ifndef _LINUX_KMSAN_TYPES_H +#define _LINUX_KMSAN_TYPES_H + +/* These constants are defined in the MSan LLVM instrumentation pass. */ +#define KMSAN_RETVAL_SIZE 800 +#define KMSAN_PARAM_SIZE 800 + +struct kmsan_context_state { + char param_tls[KMSAN_PARAM_SIZE]; + char retval_tls[KMSAN_RETVAL_SIZE]; + char va_arg_tls[KMSAN_PARAM_SIZE]; + char va_arg_origin_tls[KMSAN_PARAM_SIZE]; + u64 va_arg_overflow_size_tls; + char param_origin_tls[KMSAN_PARAM_SIZE]; + u32 retval_origin_tls; +}; + +#undef KMSAN_PARAM_SIZE +#undef KMSAN_RETVAL_SIZE + +struct kmsan_ctx { + struct kmsan_context_state cstate; + int kmsan_in_runtime; + bool allow_reporting; +}; + +#endif /* _LINUX_KMSAN_TYPES_H */ diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 5c87d0f292a2..500e536796ca 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -224,6 +224,18 @@ struct page { not kmapped, ie. highmem) */ #endif /* WANT_PAGE_VIRTUAL */ +#ifdef CONFIG_KMSAN + /* + * KMSAN metadata for this page: + * - shadow page: every bit indicates whether the corresponding + * bit of the original page is initialized (0) or not (1); + * - origin page: every 4 bytes contain an id of the stack trace + * where the uninitialized value was created. + */ + struct page *kmsan_shadow; + struct page *kmsan_origin; +#endif + #ifdef LAST_CPUPID_NOT_IN_PAGE_FLAGS int _last_cpupid; #endif diff --git a/include/linux/sched.h b/include/linux/sched.h index fbac3c19fe35..88a043f7235e 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -14,6 +14,7 @@ #include <linux/pid.h> #include <linux/sem.h> #include <linux/shm.h> +#include <linux/kmsan_types.h> #include <linux/mutex.h> #include <linux/plist.h> #include <linux/hrtimer.h> @@ -1362,6 +1363,10 @@ struct task_struct { #endif #endif +#ifdef CONFIG_KMSAN + struct kmsan_ctx kmsan_ctx; +#endif + #if IS_ENABLED(CONFIG_KUNIT) struct kunit *kunit_test; #endif diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 6d1544d9201e..0129bee7de01 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -970,6 +970,7 @@ config DEBUG_STACKOVERFLOW source "lib/Kconfig.kasan" source "lib/Kconfig.kfence" +source "lib/Kconfig.kmsan" endmenu # "Memory Debugging" diff --git a/lib/Kconfig.kmsan b/lib/Kconfig.kmsan new file mode 100644 index 000000000000..5b19dbd34d76 --- /dev/null +++ b/lib/Kconfig.kmsan @@ -0,0 +1,50 @@ +# SPDX-License-Identifier: GPL-2.0-only +config HAVE_ARCH_KMSAN + bool + +config HAVE_KMSAN_COMPILER + # Clang versions <14.0.0 also support -fsanitize=kernel-memory, but not + # all the features necessary to build the kernel with KMSAN. + depends on CC_IS_CLANG && CLANG_VERSION >= 140000 + def_bool $(cc-option,-fsanitize=kernel-memory -mllvm -msan-disable-checks=1) + +config KMSAN + bool "KMSAN: detector of uninitialized values use" + depends on HAVE_ARCH_KMSAN && HAVE_KMSAN_COMPILER + depends on SLUB && DEBUG_KERNEL && !KASAN && !KCSAN + select STACKDEPOT + select STACKDEPOT_ALWAYS_INIT + help + KernelMemorySanitizer (KMSAN) is a dynamic detector of uses of + uninitialized values in the kernel. It is based on compiler + instrumentation provided by Clang and thus requires Clang to build. + + An important note is that KMSAN is not intended for production use, + because it drastically increases kernel memory footprint and slows + the whole system down. + + See <file:Documentation/dev-tools/kmsan.rst> for more details. + +if KMSAN + +config HAVE_KMSAN_PARAM_RETVAL + # -fsanitize-memory-param-retval is supported only by Clang >= 14. + depends on HAVE_KMSAN_COMPILER + def_bool $(cc-option,-fsanitize=kernel-memory -fsanitize-memory-param-retval) + +config KMSAN_CHECK_PARAM_RETVAL + bool "Check for uninitialized values passed to and returned from functions" + default y + depends on HAVE_KMSAN_PARAM_RETVAL + help + If the compiler supports -fsanitize-memory-param-retval, KMSAN will + eagerly check every function parameter passed by value and every + function return value. + + Disabling KMSAN_CHECK_PARAM_RETVAL will result in tracking shadow for + function parameters and return values across function borders. This + is a more relaxed mode, but it generates more instrumentation code and + may potentially report errors in corner cases when non-instrumented + functions call instrumented ones. + +endif diff --git a/mm/Makefile b/mm/Makefile index a731d1decbb1..cc23b0052584 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -89,6 +89,7 @@ obj-$(CONFIG_SLAB) += slab.o obj-$(CONFIG_SLUB) += slub.o obj-$(CONFIG_KASAN) += kasan/ obj-$(CONFIG_KFENCE) += kfence/ +obj-$(CONFIG_KMSAN) += kmsan/ obj-$(CONFIG_FAILSLAB) += failslab.o obj-$(CONFIG_MEMTEST) += memtest.o obj-$(CONFIG_MIGRATION) += migrate.o diff --git a/mm/kmsan/Makefile b/mm/kmsan/Makefile new file mode 100644 index 000000000000..550ad8625e4f --- /dev/null +++ b/mm/kmsan/Makefile @@ -0,0 +1,23 @@ +# SPDX-License-Identifier: GPL-2.0 +# +# Makefile for KernelMemorySanitizer (KMSAN). +# +# +obj-y := core.o instrumentation.o hooks.o report.o shadow.o + +KMSAN_SANITIZE := n +KCOV_INSTRUMENT := n +UBSAN_SANITIZE := n + +# Disable instrumentation of KMSAN runtime with other tools. +CC_FLAGS_KMSAN_RUNTIME := -fno-stack-protector +CC_FLAGS_KMSAN_RUNTIME += $(call cc-option,-fno-conserve-stack) +CC_FLAGS_KMSAN_RUNTIME += -DDISABLE_BRANCH_PROFILING + +CFLAGS_REMOVE.o = $(CC_FLAGS_FTRACE) + +CFLAGS_core.o := $(CC_FLAGS_KMSAN_RUNTIME) +CFLAGS_hooks.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) diff --git a/mm/kmsan/core.c b/mm/kmsan/core.c new file mode 100644 index 000000000000..5330138fda5b --- /dev/null +++ b/mm/kmsan/core.c @@ -0,0 +1,440 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * KMSAN runtime library. + * + * Copyright (C) 2017-2022 Google LLC + * Author: Alexander Potapenko <glider@google.com> + * + */ + +#include <asm/page.h> +#include <linux/compiler.h> +#include <linux/export.h> +#include <linux/highmem.h> +#include <linux/interrupt.h> +#include <linux/kernel.h> +#include <linux/kmsan_types.h> +#include <linux/memory.h> +#include <linux/mm.h> +#include <linux/mm_types.h> +#include <linux/mmzone.h> +#include <linux/percpu-defs.h> +#include <linux/preempt.h> +#include <linux/slab.h> +#include <linux/stackdepot.h> +#include <linux/stacktrace.h> +#include <linux/types.h> +#include <linux/vmalloc.h> + +#include "../slab.h" +#include "kmsan.h" + +bool kmsan_enabled __read_mostly; + +/* + * Per-CPU KMSAN context to be used in interrupts, where current->kmsan is + * unavaliable. + */ +DEFINE_PER_CPU(struct kmsan_ctx, kmsan_percpu_ctx); + +void kmsan_internal_poison_memory(void *address, size_t size, gfp_t flags, + unsigned int poison_flags) +{ + u32 extra_bits = + kmsan_extra_bits(/*depth*/ 0, poison_flags & KMSAN_POISON_FREE); + bool checked = poison_flags & KMSAN_POISON_CHECK; + depot_stack_handle_t handle; + + handle = kmsan_save_stack_with_flags(flags, extra_bits); + kmsan_internal_set_shadow_origin(address, size, -1, handle, checked); +} + +void kmsan_internal_unpoison_memory(void *address, size_t size, bool checked) +{ + kmsan_internal_set_shadow_origin(address, size, 0, 0, checked); +} + +depot_stack_handle_t kmsan_save_stack_with_flags(gfp_t flags, + unsigned int extra) +{ + unsigned long entries[KMSAN_STACK_DEPTH]; + unsigned int nr_entries; + + nr_entries = stack_trace_save(entries, KMSAN_STACK_DEPTH, 0); + + /* Don't sleep (see might_sleep_if() in __alloc_pages_nodemask()). */ + flags &= ~__GFP_DIRECT_RECLAIM; + + return __stack_depot_save(entries, nr_entries, extra, flags, true); +} + +/* Copy the metadata following the memmove() behavior. */ +void kmsan_internal_memmove_metadata(void *dst, void *src, size_t n) +{ + depot_stack_handle_t old_origin = 0, new_origin = 0; + int src_slots, dst_slots, i, iter, step, skip_bits; + depot_stack_handle_t *origin_src, *origin_dst; + void *shadow_src, *shadow_dst; + u32 *align_shadow_src, shadow; + bool backwards; + + shadow_dst = kmsan_get_metadata(dst, KMSAN_META_SHADOW); + if (!shadow_dst) + return; + KMSAN_WARN_ON(!kmsan_metadata_is_contiguous(dst, n)); + + shadow_src = kmsan_get_metadata(src, KMSAN_META_SHADOW); + if (!shadow_src) { + /* + * @src is untracked: zero out destination shadow, ignore the + * origins, we're done. + */ + __memset(shadow_dst, 0, n); + return; + } + KMSAN_WARN_ON(!kmsan_metadata_is_contiguous(src, n)); + + __memmove(shadow_dst, shadow_src, n); + + origin_dst = kmsan_get_metadata(dst, KMSAN_META_ORIGIN); + origin_src = kmsan_get_metadata(src, KMSAN_META_ORIGIN); + KMSAN_WARN_ON(!origin_dst || !origin_src); + src_slots = (ALIGN((u64)src + n, KMSAN_ORIGIN_SIZE) - + ALIGN_DOWN((u64)src, KMSAN_ORIGIN_SIZE)) / + KMSAN_ORIGIN_SIZE; + dst_slots = (ALIGN((u64)dst + n, KMSAN_ORIGIN_SIZE) - + ALIGN_DOWN((u64)dst, KMSAN_ORIGIN_SIZE)) / + KMSAN_ORIGIN_SIZE; + KMSAN_WARN_ON((src_slots < 1) || (dst_slots < 1)); + KMSAN_WARN_ON((src_slots - dst_slots > 1) || + (dst_slots - src_slots < -1)); + + backwards = dst > src; + i = backwards ? min(src_slots, dst_slots) - 1 : 0; + iter = backwards ? -1 : 1; + + align_shadow_src = + (u32 *)ALIGN_DOWN((u64)shadow_src, KMSAN_ORIGIN_SIZE); + for (step = 0; step < min(src_slots, dst_slots); step++, i += iter) { + KMSAN_WARN_ON(i < 0); + shadow = align_shadow_src[i]; + if (i == 0) { + /* + * If @src isn't aligned on KMSAN_ORIGIN_SIZE, don't + * look at the first @src % KMSAN_ORIGIN_SIZE bytes + * of the first shadow slot. + */ + skip_bits = ((u64)src % KMSAN_ORIGIN_SIZE) * 8; + shadow = (shadow >> skip_bits) << skip_bits; + } + if (i == src_slots - 1) { + /* + * If @src + n isn't aligned on + * KMSAN_ORIGIN_SIZE, don't look at the last + * (@src + n) % KMSAN_ORIGIN_SIZE bytes of the + * last shadow slot. + */ + skip_bits = (((u64)src + n) % KMSAN_ORIGIN_SIZE) * 8; + shadow = (shadow << skip_bits) >> skip_bits; + } + /* + * Overwrite the origin only if the corresponding + * shadow is nonempty. + */ + if (origin_src[i] && (origin_src[i] != old_origin) && shadow) { + old_origin = origin_src[i]; + new_origin = kmsan_internal_chain_origin(old_origin); + /* + * kmsan_internal_chain_origin() may return + * NULL, but we don't want to lose the previous + * origin value. + */ + if (!new_origin) + new_origin = old_origin; + } + if (shadow) + origin_dst[i] = new_origin; + else + origin_dst[i] = 0; + } + /* + * If dst_slots is greater than src_slots (i.e. + * dst_slots == src_slots + 1), there is an extra origin slot at the + * beginning or end of the destination buffer, for which we take the + * origin from the previous slot. + * This is only done if the part of the source shadow corresponding to + * slot is non-zero. + * + * E.g. if we copy 8 aligned bytes that are marked as uninitialized + * and have origins o111 and o222, to an unaligned buffer with offset 1, + * these two origins are copied to three origin slots, so one of then + * needs to be duplicated, depending on the copy direction (@backwards) + * + * src shadow: |uuuu|uuuu|....| + * src origin: |o111|o222|....| + * + * backwards = 0: + * dst shadow: |.uuu|uuuu|u...| + * dst origin: |....|o111|o222| - fill the empty slot with o111 + * backwards = 1: + * dst shadow: |.uuu|uuuu|u...| + * dst origin: |o111|o222|....| - fill the empty slot with o222 + */ + if (src_slots < dst_slots) { + if (backwards) { + shadow = align_shadow_src[src_slots - 1]; + skip_bits = (((u64)dst + n) % KMSAN_ORIGIN_SIZE) * 8; + shadow = (shadow << skip_bits) >> skip_bits; + if (shadow) + /* src_slots > 0, therefore dst_slots is at least 2 */ + origin_dst[dst_slots - 1] = + origin_dst[dst_slots - 2]; + } else { + shadow = align_shadow_src[0]; + skip_bits = ((u64)dst % KMSAN_ORIGIN_SIZE) * 8; + shadow = (shadow >> skip_bits) << skip_bits; + if (shadow) + origin_dst[0] = origin_dst[1]; + } + } +} + +depot_stack_handle_t kmsan_internal_chain_origin(depot_stack_handle_t id) +{ + unsigned long entries[3]; + u32 extra_bits; + int depth; + bool uaf; + + if (!id) + return id; + /* + * Make sure we have enough spare bits in @id to hold the UAF bit and + * the chain depth. + */ + BUILD_BUG_ON( + (1 << STACK_DEPOT_EXTRA_BITS) <= (KMSAN_MAX_ORIGIN_DEPTH << 1)); + + extra_bits = stack_depot_get_extra_bits(id); + depth = kmsan_depth_from_eb(extra_bits); + uaf = kmsan_uaf_from_eb(extra_bits); + + /* + * Stop chaining origins once the depth reached KMSAN_MAX_ORIGIN_DEPTH. + * This mostly happens in the case structures with uninitialized padding + * are copied around many times. Origin chains for such structures are + * usually periodic, and it does not make sense to fully store them. + */ + if (depth == KMSAN_MAX_ORIGIN_DEPTH) + return id; + + depth++; + extra_bits = kmsan_extra_bits(depth, uaf); + + entries[0] = KMSAN_CHAIN_MAGIC_ORIGIN; + entries[1] = kmsan_save_stack_with_flags(GFP_ATOMIC, 0); + entries[2] = id; + /* + * @entries is a local var in non-instrumented code, so KMSAN does not + * know it is initialized. Explicitly unpoison it to avoid false + * positives when __stack_depot_save() passes it to instrumented code. + */ + kmsan_internal_unpoison_memory(entries, sizeof(entries), false); + return __stack_depot_save(entries, ARRAY_SIZE(entries), extra_bits, + GFP_ATOMIC, true); +} + +void kmsan_internal_set_shadow_origin(void *addr, size_t size, int b, + u32 origin, bool checked) +{ + u64 address = (u64)addr; + void *shadow_start; + u32 *origin_start; + size_t pad = 0; + + KMSAN_WARN_ON(!kmsan_metadata_is_contiguous(addr, size)); + shadow_start = kmsan_get_metadata(addr, KMSAN_META_SHADOW); + if (!shadow_start) { + /* + * kmsan_metadata_is_contiguous() is true, so either all shadow + * and origin pages are NULL, or all are non-NULL. + */ + if (checked) { + pr_err("%s: not memsetting %ld bytes starting at %px, because the shadow is NULL\n", + __func__, size, addr); + KMSAN_WARN_ON(true); + } + return; + } + __memset(shadow_start, b, size); + + if (!IS_ALIGNED(address, KMSAN_ORIGIN_SIZE)) { + pad = address % KMSAN_ORIGIN_SIZE; + address -= pad; + size += pad; + } + size = ALIGN(size, KMSAN_ORIGIN_SIZE); + origin_start = + (u32 *)kmsan_get_metadata((void *)address, KMSAN_META_ORIGIN); + + for (int i = 0; i < size / KMSAN_ORIGIN_SIZE; i++) + origin_start[i] = origin; +} + +struct page *kmsan_vmalloc_to_page_or_null(void *vaddr) +{ + struct page *page; + + if (!kmsan_internal_is_vmalloc_addr(vaddr) && + !kmsan_internal_is_module_addr(vaddr)) + return NULL; + page = vmalloc_to_page(vaddr); + if (pfn_valid(page_to_pfn(page))) + return page; + else + return NULL; +} + +void kmsan_internal_check_memory(void *addr, size_t size, const void *user_addr, + int reason) +{ + depot_stack_handle_t cur_origin = 0, new_origin = 0; + unsigned long addr64 = (unsigned long)addr; + depot_stack_handle_t *origin = NULL; + unsigned char *shadow = NULL; + int cur_off_start = -1; + int chunk_size; + size_t pos = 0; + + if (!size) + return; + KMSAN_WARN_ON(!kmsan_metadata_is_contiguous(addr, size)); + while (pos < size) { + chunk_size = min(size - pos, + PAGE_SIZE - ((addr64 + pos) % PAGE_SIZE)); + shadow = kmsan_get_metadata((void *)(addr64 + pos), + KMSAN_META_SHADOW); + if (!shadow) { + /* + * This page is untracked. If there were uninitialized + * bytes before, report them. + */ + if (cur_origin) { + kmsan_enter_runtime(); + kmsan_report(cur_origin, addr, size, + cur_off_start, pos - 1, user_addr, + reason); + kmsan_leave_runtime(); + } + cur_origin = 0; + cur_off_start = -1; + pos += chunk_size; + continue; + } + for (int i = 0; i < chunk_size; i++) { + if (!shadow[i]) { + /* + * This byte is unpoisoned. If there were + * poisoned bytes before, report them. + */ + if (cur_origin) { + kmsan_enter_runtime(); + kmsan_report(cur_origin, addr, size, + cur_off_start, pos + i - 1, + user_addr, reason); + kmsan_leave_runtime(); + } + cur_origin = 0; + cur_off_start = -1; + continue; + } + origin = kmsan_get_metadata((void *)(addr64 + pos + i), + KMSAN_META_ORIGIN); + KMSAN_WARN_ON(!origin); + new_origin = *origin; + /* + * Encountered new origin - report the previous + * uninitialized range. + */ + if (cur_origin != new_origin) { + if (cur_origin) { + kmsan_enter_runtime(); + kmsan_report(cur_origin, addr, size, + cur_off_start, pos + i - 1, + user_addr, reason); + kmsan_leave_runtime(); + } + cur_origin = new_origin; + cur_off_start = pos + i; + } + } + pos += chunk_size; + } + KMSAN_WARN_ON(pos != size); + if (cur_origin) { + kmsan_enter_runtime(); + kmsan_report(cur_origin, addr, size, cur_off_start, pos - 1, + user_addr, reason); + kmsan_leave_runtime(); + } +} + +bool kmsan_metadata_is_contiguous(void *addr, size_t size) +{ + char *cur_shadow = NULL, *next_shadow = NULL, *cur_origin = NULL, + *next_origin = NULL; + u64 cur_addr = (u64)addr, next_addr = cur_addr + PAGE_SIZE; + depot_stack_handle_t *origin_p; + bool all_untracked = false; + + if (!size) + return true; + + /* The whole range belongs to the same page. */ + if (ALIGN_DOWN(cur_addr + size - 1, PAGE_SIZE) == + ALIGN_DOWN(cur_addr, PAGE_SIZE)) + return true; + + cur_shadow = kmsan_get_metadata((void *)cur_addr, /*is_origin*/ false); + if (!cur_shadow) + all_untracked = true; + cur_origin = kmsan_get_metadata((void *)cur_addr, /*is_origin*/ true); + if (all_untracked && cur_origin) + goto report; + + for (; next_addr < (u64)addr + size; + cur_addr = next_addr, cur_shadow = next_shadow, + cur_origin = next_origin, next_addr += PAGE_SIZE) { + next_shadow = kmsan_get_metadata((void *)next_addr, false); + next_origin = kmsan_get_metadata((void *)next_addr, true); + if (all_untracked) { + if (next_shadow || next_origin) + goto report; + if (!next_shadow && !next_origin) + continue; + } + if (((u64)cur_shadow == ((u64)next_shadow - PAGE_SIZE)) && + ((u64)cur_origin == ((u64)next_origin - PAGE_SIZE))) + continue; + goto report; + } + return true; + +report: + pr_err("%s: attempting to access two shadow page ranges.\n", __func__); + pr_err("Access of size %ld at %px.\n", size, addr); + pr_err("Addresses belonging to different ranges: %px and %px\n", + (void *)cur_addr, (void *)next_addr); + pr_err("page[0].shadow: %px, page[1].shadow: %px\n", cur_shadow, + next_shadow); + pr_err("page[0].origin: %px, page[1].origin: %px\n", cur_origin, + next_origin); + origin_p = kmsan_get_metadata(addr, KMSAN_META_ORIGIN); + if (origin_p) { + pr_err("Origin: %08x\n", *origin_p); + kmsan_print_origin(*origin_p); + } else { + pr_err("Origin: unavailable\n"); + } + return false; +} diff --git a/mm/kmsan/hooks.c b/mm/kmsan/hooks.c new file mode 100644 index 000000000000..4ac62fa67a02 --- /dev/null +++ b/mm/kmsan/hooks.c @@ -0,0 +1,66 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * KMSAN hooks for kernel subsystems. + * + * These functions handle creation of KMSAN metadata for memory allocations. + * + * Copyright (C) 2018-2022 Google LLC + * Author: Alexander Potapenko <glider@google.com> + * + */ + +#include <linux/cacheflush.h> +#include <linux/gfp.h> +#include <linux/mm.h> +#include <linux/mm_types.h> +#include <linux/slab.h> +#include <linux/uaccess.h> + +#include "../internal.h" +#include "../slab.h" +#include "kmsan.h" + +/* + * Instrumented functions shouldn't be called under + * kmsan_enter_runtime()/kmsan_leave_runtime(), because this will lead to + * skipping effects of functions like memset() inside instrumented code. + */ + +/* Functions from kmsan-checks.h follow. */ +void kmsan_poison_memory(const void *address, size_t size, gfp_t flags) +{ + if (!kmsan_enabled || kmsan_in_runtime()) + return; + kmsan_enter_runtime(); + /* The users may want to poison/unpoison random memory. */ + kmsan_internal_poison_memory((void *)address, size, flags, + KMSAN_POISON_NOCHECK); + kmsan_leave_runtime(); +} +EXPORT_SYMBOL(kmsan_poison_memory); + +void kmsan_unpoison_memory(const void *address, size_t size) +{ + unsigned long ua_flags; + + if (!kmsan_enabled || kmsan_in_runtime()) + return; + + ua_flags = user_access_save(); + kmsan_enter_runtime(); + /* The users may want to poison/unpoison random memory. */ + kmsan_internal_unpoison_memory((void *)address, size, + KMSAN_POISON_NOCHECK); + kmsan_leave_runtime(); + user_access_restore(ua_flags); +} +EXPORT_SYMBOL(kmsan_unpoison_memory); + +void kmsan_check_memory(const void *addr, size_t size) +{ + if (!kmsan_enabled) + return; + return kmsan_internal_check_memory((void *)addr, size, /*user_addr*/ 0, + REASON_ANY); +} +EXPORT_SYMBOL(kmsan_check_memory); diff --git a/mm/kmsan/instrumentation.c b/mm/kmsan/instrumentation.c new file mode 100644 index 000000000000..280d15413268 --- /dev/null +++ b/mm/kmsan/instrumentation.c @@ -0,0 +1,307 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * KMSAN compiler API. + * + * This file implements __msan_XXX hooks that Clang inserts into the code + * compiled with -fsanitize=kernel-memory. + * See Documentation/dev-tools/kmsan.rst for more information on how KMSAN + * instrumentation works. + * + * Copyright (C) 2017-2022 Google LLC + * Author: Alexander Potapenko <glider@google.com> + * + */ + +#include "kmsan.h" +#include <linux/gfp.h> +#include <linux/mm.h> +#include <linux/uaccess.h> + +static inline bool is_bad_asm_addr(void *addr, uintptr_t size, bool is_store) +{ + if ((u64)addr < TASK_SIZE) + return true; + if (!kmsan_get_metadata(addr, KMSAN_META_SHADOW)) + return true; + return false; +} + +static inline struct shadow_origin_ptr +get_shadow_origin_ptr(void *addr, u64 size, bool store) +{ + unsigned long ua_flags = user_access_save(); + struct shadow_origin_ptr ret; + + ret = kmsan_get_shadow_origin_ptr(addr, size, store); + user_access_restore(ua_flags); + return ret; +} + +/* Get shadow and origin pointers for a memory load with non-standard size. */ +struct shadow_origin_ptr __msan_metadata_ptr_for_load_n(void *addr, + uintptr_t size) +{ + return get_shadow_origin_ptr(addr, size, /*store*/ false); +} +EXPORT_SYMBOL(__msan_metadata_ptr_for_load_n); + +/* Get shadow and origin pointers for a memory store with non-standard size. */ +struct shadow_origin_ptr __msan_metadata_ptr_for_store_n(void *addr, + uintptr_t size) +{ + return get_shadow_origin_ptr(addr, size, /*store*/ true); +} +EXPORT_SYMBOL(__msan_metadata_ptr_for_store_n); + +/* + * Declare functions that obtain shadow/origin pointers for loads and stores + * with fixed size. + */ +#define DECLARE_METADATA_PTR_GETTER(size) \ + struct shadow_origin_ptr __msan_metadata_ptr_for_load_##size( \ + void *addr) \ + { \ + return get_shadow_origin_ptr(addr, size, /*store*/ false); \ + } \ + EXPORT_SYMBOL(__msan_metadata_ptr_for_load_##size); \ + struct shadow_origin_ptr __msan_metadata_ptr_for_store_##size( \ + void *addr) \ + { \ + return get_shadow_origin_ptr(addr, size, /*store*/ true); \ + } \ + EXPORT_SYMBOL(__msan_metadata_ptr_for_store_##size) + +DECLARE_METADATA_PTR_GETTER(1); +DECLARE_METADATA_PTR_GETTER(2); +DECLARE_METADATA_PTR_GETTER(4); +DECLARE_METADATA_PTR_GETTER(8); + +/* + * Handle a memory store performed by inline assembly. KMSAN conservatively + * attempts to unpoison the outputs of asm() directives to prevent false + * positives caused by missed stores. + */ +void __msan_instrument_asm_store(void *addr, uintptr_t size) +{ + unsigned long ua_flags; + + if (!kmsan_enabled || kmsan_in_runtime()) + return; + + ua_flags = user_access_save(); + /* + * Most of the accesses are below 32 bytes. The two exceptions so far + * are clwb() (64 bytes) and FPU state (512 bytes). + * It's unlikely that the assembly will touch more than 512 bytes. + */ + if (size > 512) { + WARN_ONCE(1, "assembly store size too big: %ld\n", size); + size = 8; + } + if (is_bad_asm_addr(addr, size, /*is_store*/ true)) { + user_access_restore(ua_flags); + return; + } + kmsan_enter_runtime(); + /* Unpoisoning the memory on best effort. */ + kmsan_internal_unpoison_memory(addr, size, /*checked*/ false); + kmsan_leave_runtime(); + user_access_restore(ua_flags); +} +EXPORT_SYMBOL(__msan_instrument_asm_store); + +/* + * KMSAN instrumentation pass replaces LLVM memcpy, memmove and memset + * intrinsics with calls to respective __msan_ functions. We use + * get_param0_metadata() and set_retval_metadata() to store the shadow/origin + * values for the destination argument of these functions and use them for the + * functions' return values. + */ +static inline void get_param0_metadata(u64 *shadow, + depot_stack_handle_t *origin) +{ + struct kmsan_ctx *ctx = kmsan_get_context(); + + *shadow = *(u64 *)(ctx->cstate.param_tls); + *origin = ctx->cstate.param_origin_tls[0]; +} + +static inline void set_retval_metadata(u64 shadow, depot_stack_handle_t origin) +{ + struct kmsan_ctx *ctx = kmsan_get_context(); + + *(u64 *)(ctx->cstate.retval_tls) = shadow; + ctx->cstate.retval_origin_tls = origin; +} + +/* Handle llvm.memmove intrinsic. */ +void *__msan_memmove(void *dst, const void *src, uintptr_t n) +{ + depot_stack_handle_t origin; + void *result; + u64 shadow; + + get_param0_metadata(&shadow, &origin); + result = __memmove(dst, src, n); + if (!n) + /* Some people call memmove() with zero length. */ + return result; + if (!kmsan_enabled || kmsan_in_runtime()) + return result; + + kmsan_enter_runtime(); + kmsan_internal_memmove_metadata(dst, (void *)src, n); + kmsan_leave_runtime(); + + set_retval_metadata(shadow, origin); + return result; +} +EXPORT_SYMBOL(__msan_memmove); + +/* Handle llvm.memcpy intrinsic. */ +void *__msan_memcpy(void *dst, const void *src, uintptr_t n) +{ + depot_stack_handle_t origin; + void *result; + u64 shadow; + + get_param0_metadata(&shadow, &origin); + result = __memcpy(dst, src, n); + if (!n) + /* Some people call memcpy() with zero length. */ + return result; + + if (!kmsan_enabled || kmsan_in_runtime()) + return result; + + kmsan_enter_runtime(); + /* Using memmove instead of memcpy doesn't affect correctness. */ + kmsan_internal_memmove_metadata(dst, (void *)src, n); + kmsan_leave_runtime(); + + set_retval_metadata(shadow, origin); + return result; +} +EXPORT_SYMBOL(__msan_memcpy); + +/* Handle llvm.memset intrinsic. */ +void *__msan_memset(void *dst, int c, uintptr_t n) +{ + depot_stack_handle_t origin; + void *result; + u64 shadow; + + get_param0_metadata(&shadow, &origin); + result = __memset(dst, c, n); + if (!kmsan_enabled || kmsan_in_runtime()) + return result; + + kmsan_enter_runtime(); + /* + * Clang doesn't pass parameter metadata here, so it is impossible to + * use shadow of @c to set up the shadow for @dst. + */ + kmsan_internal_unpoison_memory(dst, n, /*checked*/ false); + kmsan_leave_runtime(); + + set_retval_metadata(shadow, origin); + return result; +} +EXPORT_SYMBOL(__msan_memset); + +/* + * Create a new origin from an old one. This is done when storing an + * uninitialized value to memory. When reporting an error, KMSAN unrolls and + * prints the whole chain of stores that preceded the use of this value. + */ +depot_stack_handle_t __msan_chain_origin(depot_stack_handle_t origin) +{ + depot_stack_handle_t ret = 0; + unsigned long ua_flags; + + if (!kmsan_enabled || kmsan_in_runtime()) + return ret; + + ua_flags = user_access_save(); + + /* Creating new origins may allocate memory. */ + kmsan_enter_runtime(); + ret = kmsan_internal_chain_origin(origin); + kmsan_leave_runtime(); + user_access_restore(ua_flags); + return ret; +} +EXPORT_SYMBOL(__msan_chain_origin); + +/* Poison a local variable when entering a function. */ +void __msan_poison_alloca(void *address, uintptr_t size, char *descr) +{ + depot_stack_handle_t handle; + unsigned long entries[4]; + unsigned long ua_flags; + + if (!kmsan_enabled || kmsan_in_runtime()) + return; + + ua_flags = user_access_save(); + entries[0] = KMSAN_ALLOCA_MAGIC_ORIGIN; + entries[1] = (u64)descr; + entries[2] = (u64)__builtin_return_address(0); + /* + * With frame pointers enabled, it is possible to quickly fetch the + * second frame of the caller stack without calling the unwinder. + * Without them, simply do not bother. + */ + if (IS_ENABLED(CONFIG_UNWINDER_FRAME_POINTER)) + entries[3] = (u64)__builtin_return_address(1); + else + entries[3] = 0; + + /* stack_depot_save() may allocate memory. */ + kmsan_enter_runtime(); + handle = stack_depot_save(entries, ARRAY_SIZE(entries), GFP_ATOMIC); + kmsan_leave_runtime(); + + kmsan_internal_set_shadow_origin(address, size, -1, handle, + /*checked*/ true); + user_access_restore(ua_flags); +} +EXPORT_SYMBOL(__msan_poison_alloca); + +/* Unpoison a local variable. */ +void __msan_unpoison_alloca(void *address, uintptr_t size) +{ + if (!kmsan_enabled || kmsan_in_runtime()) + return; + + kmsan_enter_runtime(); + kmsan_internal_unpoison_memory(address, size, /*checked*/ true); + kmsan_leave_runtime(); +} +EXPORT_SYMBOL(__msan_unpoison_alloca); + +/* + * Report that an uninitialized value with the given origin was used in a way + * that constituted undefined behavior. + */ +void __msan_warning(u32 origin) +{ + if (!kmsan_enabled || kmsan_in_runtime()) + return; + kmsan_enter_runtime(); + kmsan_report(origin, /*address*/ 0, /*size*/ 0, + /*off_first*/ 0, /*off_last*/ 0, /*user_addr*/ 0, + REASON_ANY); + kmsan_leave_runtime(); +} +EXPORT_SYMBOL(__msan_warning); + +/* + * At the beginning of an instrumented function, obtain the pointer to + * `struct kmsan_context_state` holding the metadata for function parameters. + */ +struct kmsan_context_state *__msan_get_context_state(void) +{ + return &kmsan_get_context()->cstate; +} +EXPORT_SYMBOL(__msan_get_context_state); diff --git a/mm/kmsan/kmsan.h b/mm/kmsan/kmsan.h new file mode 100644 index 000000000000..97d48b45dba5 --- /dev/null +++ b/mm/kmsan/kmsan.h @@ -0,0 +1,204 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Functions used by the KMSAN runtime. + * + * Copyright (C) 2017-2022 Google LLC + * Author: Alexander Potapenko <glider@google.com> + * + */ + +#ifndef __MM_KMSAN_KMSAN_H +#define __MM_KMSAN_KMSAN_H + +#include <asm/pgtable_64_types.h> +#include <linux/irqflags.h> +#include <linux/sched.h> +#include <linux/stackdepot.h> +#include <linux/stacktrace.h> +#include <linux/nmi.h> +#include <linux/mm.h> +#include <linux/printk.h> + +#define KMSAN_ALLOCA_MAGIC_ORIGIN 0xabcd0100 +#define KMSAN_CHAIN_MAGIC_ORIGIN 0xabcd0200 + +#define KMSAN_POISON_NOCHECK 0x0 +#define KMSAN_POISON_CHECK 0x1 +#define KMSAN_POISON_FREE 0x2 + +#define KMSAN_ORIGIN_SIZE 4 +#define KMSAN_MAX_ORIGIN_DEPTH 7 + +#define KMSAN_STACK_DEPTH 64 + +#define KMSAN_META_SHADOW (false) +#define KMSAN_META_ORIGIN (true) + +extern bool kmsan_enabled; +extern int panic_on_kmsan; + +/* + * KMSAN performs a lot of consistency checks that are currently enabled by + * default. BUG_ON is normally discouraged in the kernel, unless used for + * debugging, but KMSAN itself is a debugging tool, so it makes little sense to + * recover if something goes wrong. + */ +#define KMSAN_WARN_ON(cond) \ + ({ \ + const bool __cond = WARN_ON(cond); \ + if (unlikely(__cond)) { \ + WRITE_ONCE(kmsan_enabled, false); \ + if (panic_on_kmsan) { \ + /* Can't call panic() here because */ \ + /* of uaccess checks. */ \ + BUG(); \ + } \ + } \ + __cond; \ + }) + +/* + * A pair of metadata pointers to be returned by the instrumentation functions. + */ +struct shadow_origin_ptr { + void *shadow, *origin; +}; + +struct shadow_origin_ptr kmsan_get_shadow_origin_ptr(void *addr, u64 size, + bool store); +void *kmsan_get_metadata(void *addr, bool is_origin); + +enum kmsan_bug_reason { + REASON_ANY, + REASON_COPY_TO_USER, + REASON_SUBMIT_URB, +}; + +void kmsan_print_origin(depot_stack_handle_t origin); + +/** + * kmsan_report() - Report a use of uninitialized value. + * @origin: Stack ID of the uninitialized value. + * @address: Address at which the memory access happens. + * @size: Memory access size. + * @off_first: Offset (from @address) of the first byte to be reported. + * @off_last: Offset (from @address) of the last byte to be reported. + * @user_addr: When non-NULL, denotes the userspace address to which the kernel + * is leaking data. + * @reason: Error type from enum kmsan_bug_reason. + * + * kmsan_report() prints an error message for a consequent group of bytes + * sharing the same origin. If an uninitialized value is used in a comparison, + * this function is called once without specifying the addresses. When checking + * a memory range, KMSAN may call kmsan_report() multiple times with the same + * @address, @size, @user_addr and @reason, but different @off_first and + * @off_last corresponding to different @origin values. + */ +void kmsan_report(depot_stack_handle_t origin, void *address, int size, + int off_first, int off_last, const void *user_addr, + enum kmsan_bug_reason reason); + +DECLARE_PER_CPU(struct kmsan_ctx, kmsan_percpu_ctx); + +static __always_inline struct kmsan_ctx *kmsan_get_context(void) +{ + return in_task() ? ¤t->kmsan_ctx : raw_cpu_ptr(&kmsan_percpu_ctx); +} + +/* + * When a compiler hook or KMSAN runtime function is invoked, it may make a + * call to instrumented code and eventually call itself recursively. To avoid + * that, we guard the runtime entry regions with + * kmsan_enter_runtime()/kmsan_leave_runtime() and exit the hook if + * kmsan_in_runtime() is true. + * + * Non-runtime code may occasionally get executed in nested IRQs from the + * runtime code (e.g. when called via smp_call_function_single()). Because some + * KMSAN routines may take locks (e.g. for memory allocation), we conservatively + * bail out instead of calling them. To minimize the effect of this (potentially + * missing initialization events) kmsan_in_runtime() is not checked in + * non-blocking runtime functions. + */ +static __always_inline bool kmsan_in_runtime(void) +{ + if ((hardirq_count() >> HARDIRQ_SHIFT) > 1) + return true; + return kmsan_get_context()->kmsan_in_runtime; +} + +static __always_inline void kmsan_enter_runtime(void) +{ + struct kmsan_ctx *ctx; + + ctx = kmsan_get_context(); + KMSAN_WARN_ON(ctx->kmsan_in_runtime++); +} + +static __always_inline void kmsan_leave_runtime(void) +{ + struct kmsan_ctx *ctx = kmsan_get_context(); + + KMSAN_WARN_ON(--ctx->kmsan_in_runtime); +} + +depot_stack_handle_t kmsan_save_stack(void); +depot_stack_handle_t kmsan_save_stack_with_flags(gfp_t flags, + unsigned int extra_bits); + +/* + * Pack and unpack the origin chain depth and UAF flag to/from the extra bits + * provided by the stack depot. + * The UAF flag is stored in the lowest bit, followed by the depth in the upper + * bits. + * set_dsh_extra_bits() is responsible for clamping the value. + */ +static __always_inline unsigned int kmsan_extra_bits(unsigned int depth, + bool uaf) +{ + return (depth << 1) | uaf; +} + +static __always_inline bool kmsan_uaf_from_eb(unsigned int extra_bits) +{ + return extra_bits & 1; +} + +static __always_inline unsigned int kmsan_depth_from_eb(unsigned int extra_bits) +{ + return extra_bits >> 1; +} + +/* + * kmsan_internal_ functions are supposed to be very simple and not require the + * kmsan_in_runtime() checks. + */ +void kmsan_internal_memmove_metadata(void *dst, void *src, size_t n); +void kmsan_internal_poison_memory(void *address, size_t size, gfp_t flags, + unsigned int poison_flags); +void kmsan_internal_unpoison_memory(void *address, size_t size, bool checked); +void kmsan_internal_set_shadow_origin(void *address, size_t size, int b, + u32 origin, bool checked); +depot_stack_handle_t kmsan_internal_chain_origin(depot_stack_handle_t id); + +bool kmsan_metadata_is_contiguous(void *addr, size_t size); +void kmsan_internal_check_memory(void *addr, size_t size, const void *user_addr, + int reason); + +struct page *kmsan_vmalloc_to_page_or_null(void *vaddr); + +/* + * kmsan_internal_is_module_addr() and kmsan_internal_is_vmalloc_addr() are + * non-instrumented versions of is_module_address() and is_vmalloc_addr() that + * are safe to call from KMSAN runtime without recursion. + */ +static inline bool kmsan_internal_is_module_addr(void *vaddr) +{ + return ((u64)vaddr >= MODULES_VADDR) && ((u64)vaddr < MODULES_END); +} + +static inline bool kmsan_internal_is_vmalloc_addr(void *addr) +{ + return ((u64)addr >= VMALLOC_START) && ((u64)addr < VMALLOC_END); +} + +#endif /* __MM_KMSAN_KMSAN_H */ diff --git a/mm/kmsan/report.c b/mm/kmsan/report.c new file mode 100644 index 000000000000..02736ec757f2 --- /dev/null +++ b/mm/kmsan/report.c @@ -0,0 +1,219 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * KMSAN error reporting routines. + * + * Copyright (C) 2019-2022 Google LLC + * Author: Alexander Potapenko <glider@google.com> + * + */ + +#include <linux/console.h> +#include <linux/moduleparam.h> +#include <linux/stackdepot.h> +#include <linux/stacktrace.h> +#include <linux/uaccess.h> + +#include "kmsan.h" + +static DEFINE_RAW_SPINLOCK(kmsan_report_lock); +#define DESCR_SIZE 128 +/* Protected by kmsan_report_lock */ +static char report_local_descr[DESCR_SIZE]; +int panic_on_kmsan __read_mostly; + +#ifdef MODULE_PARAM_PREFIX +#undef MODULE_PARAM_PREFIX +#endif +#define MODULE_PARAM_PREFIX "kmsan." +module_param_named(panic, panic_on_kmsan, int, 0); + +/* + * Skip internal KMSAN frames. + */ +static int get_stack_skipnr(const unsigned long stack_entries[], + int num_entries) +{ + int len, skip; + char buf[64]; + + for (skip = 0; skip < num_entries; ++skip) { + len = scnprintf(buf, sizeof(buf), "%ps", + (void *)stack_entries[skip]); + + /* Never show __msan_* or kmsan_* functions. */ + if ((strnstr(buf, "__msan_", len) == buf) || + (strnstr(buf, "kmsan_", len) == buf)) + continue; + + /* + * No match for runtime functions -- @skip entries to skip to + * get to first frame of interest. + */ + break; + } + + return skip; +} + +/* + * Currently the descriptions of locals generated by Clang look as follows: + * ----local_name@function_name + * We want to print only the name of the local, as other information in that + * description can be confusing. + * The meaningful part of the description is copied to a global buffer to avoid + * allocating memory. + */ +static char *pretty_descr(char *descr) +{ + int pos = 0, len = strlen(descr); + + for (int i = 0; i < len; i++) { + if (descr[i] == '@') + break; + if (descr[i] == '-') + continue; + report_local_descr[pos] = descr[i]; + if (pos + 1 == DESCR_SIZE) + break; + pos++; + } + report_local_descr[pos] = 0; + return report_local_descr; +} + +void kmsan_print_origin(depot_stack_handle_t origin) +{ + unsigned long *entries = NULL, *chained_entries = NULL; + unsigned int nr_entries, chained_nr_entries, skipnr; + void *pc1 = NULL, *pc2 = NULL; + depot_stack_handle_t head; + unsigned long magic; + char *descr = NULL; + unsigned int depth; + + if (!origin) + return; + + while (true) { + nr_entries = stack_depot_fetch(origin, &entries); + depth = kmsan_depth_from_eb(stack_depot_get_extra_bits(origin)); + magic = nr_entries ? entries[0] : 0; + if ((nr_entries == 4) && (magic == KMSAN_ALLOCA_MAGIC_ORIGIN)) { + descr = (char *)entries[1]; + pc1 = (void *)entries[2]; + pc2 = (void *)entries[3]; + pr_err("Local variable %s created at:\n", + pretty_descr(descr)); + if (pc1) + pr_err(" %pSb\n", pc1); + if (pc2) + pr_err(" %pSb\n", pc2); + break; + } + if ((nr_entries == 3) && (magic == KMSAN_CHAIN_MAGIC_ORIGIN)) { + /* + * Origin chains deeper than KMSAN_MAX_ORIGIN_DEPTH are + * not stored, so the output may be incomplete. + */ + if (depth == KMSAN_MAX_ORIGIN_DEPTH) + pr_err("<Zero or more stacks not recorded to save memory>\n\n"); + head = entries[1]; + origin = entries[2]; + pr_err("Uninit was stored to memory at:\n"); + chained_nr_entries = + stack_depot_fetch(head, &chained_entries); + kmsan_internal_unpoison_memory( + chained_entries, + chained_nr_entries * sizeof(*chained_entries), + /*checked*/ false); + skipnr = get_stack_skipnr(chained_entries, + chained_nr_entries); + stack_trace_print(chained_entries + skipnr, + chained_nr_entries - skipnr, 0); + pr_err("\n"); + continue; + } + pr_err("Uninit was created at:\n"); + if (nr_entries) { + skipnr = get_stack_skipnr(entries, nr_entries); + stack_trace_print(entries + skipnr, nr_entries - skipnr, + 0); + } else { + pr_err("(stack is not available)\n"); + } + break; + } +} + +void kmsan_report(depot_stack_handle_t origin, void *address, int size, + int off_first, int off_last, const void *user_addr, + enum kmsan_bug_reason reason) +{ + unsigned long stack_entries[KMSAN_STACK_DEPTH]; + int num_stack_entries, skipnr; + char *bug_type = NULL; + unsigned long ua_flags; + bool is_uaf; + + if (!kmsan_enabled) + return; + if (!current->kmsan_ctx.allow_reporting) + return; + if (!origin) + return; + + current->kmsan_ctx.allow_reporting = false; + ua_flags = user_access_save(); + raw_spin_lock(&kmsan_report_lock); + pr_err("=====================================================\n"); + is_uaf = kmsan_uaf_from_eb(stack_depot_get_extra_bits(origin)); + switch (reason) { + case REASON_ANY: + bug_type = is_uaf ? "use-after-free" : "uninit-value"; + break; + case REASON_COPY_TO_USER: + bug_type = is_uaf ? "kernel-infoleak-after-free" : + "kernel-infoleak"; + break; + case REASON_SUBMIT_URB: + bug_type = is_uaf ? "kernel-usb-infoleak-after-free" : + "kernel-usb-infoleak"; + break; + } + + num_stack_entries = + stack_trace_save(stack_entries, KMSAN_STACK_DEPTH, 1); + skipnr = get_stack_skipnr(stack_entries, num_stack_entries); + + pr_err("BUG: KMSAN: %s in %pSb\n", bug_type, + (void *)stack_entries[skipnr]); + stack_trace_print(stack_entries + skipnr, num_stack_entries - skipnr, + 0); + pr_err("\n"); + + kmsan_print_origin(origin); + + if (size) { + pr_err("\n"); + if (off_first == off_last) + pr_err("Byte %d of %d is uninitialized\n", off_first, + size); + else + pr_err("Bytes %d-%d of %d are uninitialized\n", + off_first, off_last, size); + } + if (address) + pr_err("Memory access of size %d starts at %px\n", size, + address); + if (user_addr && reason == REASON_COPY_TO_USER) + pr_err("Data copied to user address %px\n", user_addr); + pr_err("\n"); + dump_stack_print_info(KERN_ERR); + pr_err("=====================================================\n"); + add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE); + raw_spin_unlock(&kmsan_report_lock); + if (panic_on_kmsan) + panic("kmsan.panic set ...\n"); + user_access_restore(ua_flags); + current->kmsan_ctx.allow_reporting = true; +} diff --git a/mm/kmsan/shadow.c b/mm/kmsan/shadow.c new file mode 100644 index 000000000000..acc5279acc3b --- /dev/null +++ b/mm/kmsan/shadow.c @@ -0,0 +1,147 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * KMSAN shadow implementation. + * + * Copyright (C) 2017-2022 Google LLC + * Author: Alexander Potapenko <glider@google.com> + * + */ + +#include <asm/kmsan.h> +#include <asm/tlbflush.h> +#include <linux/cacheflush.h> +#include <linux/memblock.h> +#include <linux/mm_types.h> +#include <linux/percpu-defs.h> +#include <linux/slab.h> +#include <linux/smp.h> +#include <linux/stddef.h> + +#include "../internal.h" +#include "kmsan.h" + +#define shadow_page_for(page) ((page)->kmsan_shadow) + +#define origin_page_for(page) ((page)->kmsan_origin) + +static void *shadow_ptr_for(struct page *page) +{ + return page_address(shadow_page_for(page)); +} + +static void *origin_ptr_for(struct page *page) +{ + return page_address(origin_page_for(page)); +} + +static bool page_has_metadata(struct page *page) +{ + return shadow_page_for(page) && origin_page_for(page); +} + +static void set_no_shadow_origin_page(struct page *page) +{ + shadow_page_for(page) = NULL; + origin_page_for(page) = NULL; +} + +/* + * Dummy load and store pages to be used when the real metadata is unavailable. + * There are separate pages for loads and stores, so that every load returns a + * zero, and every store doesn't affect other loads. + */ +static char dummy_load_page[PAGE_SIZE] __aligned(PAGE_SIZE); +static char dummy_store_page[PAGE_SIZE] __aligned(PAGE_SIZE); + +static unsigned long vmalloc_meta(void *addr, bool is_origin) +{ + unsigned long addr64 = (unsigned long)addr, off; + + KMSAN_WARN_ON(is_origin && !IS_ALIGNED(addr64, KMSAN_ORIGIN_SIZE)); + if (kmsan_internal_is_vmalloc_addr(addr)) { + off = addr64 - VMALLOC_START; + return off + (is_origin ? KMSAN_VMALLOC_ORIGIN_START : + KMSAN_VMALLOC_SHADOW_START); + } + if (kmsan_internal_is_module_addr(addr)) { + off = addr64 - MODULES_VADDR; + return off + (is_origin ? KMSAN_MODULES_ORIGIN_START : + KMSAN_MODULES_SHADOW_START); + } + return 0; +} + +static struct page *virt_to_page_or_null(void *vaddr) +{ + if (kmsan_virt_addr_valid(vaddr)) + return virt_to_page(vaddr); + else + return NULL; +} + +struct shadow_origin_ptr kmsan_get_shadow_origin_ptr(void *address, u64 size, + bool store) +{ + struct shadow_origin_ptr ret; + void *shadow; + + /* + * Even if we redirect this memory access to the dummy page, it will + * go out of bounds. + */ + KMSAN_WARN_ON(size > PAGE_SIZE); + + if (!kmsan_enabled) + goto return_dummy; + + KMSAN_WARN_ON(!kmsan_metadata_is_contiguous(address, size)); + shadow = kmsan_get_metadata(address, KMSAN_META_SHADOW); + if (!shadow) + goto return_dummy; + + ret.shadow = shadow; + ret.origin = kmsan_get_metadata(address, KMSAN_META_ORIGIN); + return ret; + +return_dummy: + if (store) { + /* Ignore this store. */ + ret.shadow = dummy_store_page; + ret.origin = dummy_store_page; + } else { + /* This load will return zero. */ + ret.shadow = dummy_load_page; + ret.origin = dummy_load_page; + } + return ret; +} + +/* + * Obtain the shadow or origin pointer for the given address, or NULL if there's + * none. The caller must check the return value for being non-NULL if needed. + * The return value of this function should not depend on whether we're in the + * runtime or not. + */ +void *kmsan_get_metadata(void *address, bool is_origin) +{ + u64 addr = (u64)address, pad, off; + struct page *page; + + if (is_origin && !IS_ALIGNED(addr, KMSAN_ORIGIN_SIZE)) { + pad = addr % KMSAN_ORIGIN_SIZE; + addr -= pad; + } + address = (void *)addr; + if (kmsan_internal_is_vmalloc_addr(address) || + kmsan_internal_is_module_addr(address)) + return (void *)vmalloc_meta(address, is_origin); + + page = virt_to_page_or_null(address); + if (!page) + return NULL; + if (!page_has_metadata(page)) + return NULL; + off = addr % PAGE_SIZE; + + return (is_origin ? origin_ptr_for(page) : shadow_ptr_for(page)) + off; +} diff --git a/scripts/Makefile.kmsan b/scripts/Makefile.kmsan new file mode 100644 index 000000000000..b5b0aa61322e --- /dev/null +++ b/scripts/Makefile.kmsan @@ -0,0 +1,8 @@ +# SPDX-License-Identifier: GPL-2.0 +kmsan-cflags := -fsanitize=kernel-memory + +ifdef CONFIG_KMSAN_CHECK_PARAM_RETVAL +kmsan-cflags += -fsanitize-memory-param-retval +endif + +export CFLAGS_KMSAN := $(kmsan-cflags) diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib index 3fb6a99e78c4..ac32429e93b7 100644 --- a/scripts/Makefile.lib +++ b/scripts/Makefile.lib @@ -157,6 +157,15 @@ _c_flags += $(if $(patsubst n%,, \ endif endif +ifeq ($(CONFIG_KMSAN),y) +_c_flags += $(if $(patsubst n%,, \ + $(KMSAN_SANITIZE_$(basetarget).o)$(KMSAN_SANITIZE)y), \ + $(CFLAGS_KMSAN)) +_c_flags += $(if $(patsubst n%,, \ + $(KMSAN_ENABLE_CHECKS_$(basetarget).o)$(KMSAN_ENABLE_CHECKS)y), \ + , -mllvm -msan-disable-checks=1) +endif + ifeq ($(CONFIG_UBSAN),y) _c_flags += $(if $(patsubst n%,, \ $(UBSAN_SANITIZE_$(basetarget).o)$(UBSAN_SANITIZE)$(CONFIG_UBSAN_SANITIZE_ALL)), \ |