1 /* SPDX-License-Identifier: GPL-2.0 */ 2 /* 3 * Functions used by the KMSAN runtime. 4 * 5 * Copyright (C) 2017-2022 Google LLC 6 * Author: Alexander Potapenko <glider@google.com> 7 * 8 */ 9 10 #ifndef __MM_KMSAN_KMSAN_H 11 #define __MM_KMSAN_KMSAN_H 12 13 #include <asm/pgtable_64_types.h> 14 #include <linux/irqflags.h> 15 #include <linux/sched.h> 16 #include <linux/stackdepot.h> 17 #include <linux/stacktrace.h> 18 #include <linux/nmi.h> 19 #include <linux/mm.h> 20 #include <linux/printk.h> 21 22 #define KMSAN_ALLOCA_MAGIC_ORIGIN 0xabcd0100 23 #define KMSAN_CHAIN_MAGIC_ORIGIN 0xabcd0200 24 25 #define KMSAN_POISON_NOCHECK 0x0 26 #define KMSAN_POISON_CHECK 0x1 27 #define KMSAN_POISON_FREE 0x2 28 29 #define KMSAN_ORIGIN_SIZE 4 30 #define KMSAN_MAX_ORIGIN_DEPTH 7 31 32 #define KMSAN_STACK_DEPTH 64 33 34 #define KMSAN_META_SHADOW (false) 35 #define KMSAN_META_ORIGIN (true) 36 37 extern bool kmsan_enabled; 38 extern int panic_on_kmsan; 39 40 /* 41 * KMSAN performs a lot of consistency checks that are currently enabled by 42 * default. BUG_ON is normally discouraged in the kernel, unless used for 43 * debugging, but KMSAN itself is a debugging tool, so it makes little sense to 44 * recover if something goes wrong. 45 */ 46 #define KMSAN_WARN_ON(cond) \ 47 ({ \ 48 const bool __cond = WARN_ON(cond); \ 49 if (unlikely(__cond)) { \ 50 WRITE_ONCE(kmsan_enabled, false); \ 51 if (panic_on_kmsan) { \ 52 /* Can't call panic() here because */ \ 53 /* of uaccess checks. */ \ 54 BUG(); \ 55 } \ 56 } \ 57 __cond; \ 58 }) 59 60 /* 61 * A pair of metadata pointers to be returned by the instrumentation functions. 62 */ 63 struct shadow_origin_ptr { 64 void *shadow, *origin; 65 }; 66 67 struct shadow_origin_ptr kmsan_get_shadow_origin_ptr(void *addr, u64 size, 68 bool store); 69 void *kmsan_get_metadata(void *addr, bool is_origin); 70 void __init kmsan_init_alloc_meta_for_range(void *start, void *end); 71 72 enum kmsan_bug_reason { 73 REASON_ANY, 74 REASON_COPY_TO_USER, 75 REASON_SUBMIT_URB, 76 }; 77 78 void kmsan_print_origin(depot_stack_handle_t origin); 79 80 /** 81 * kmsan_report() - Report a use of uninitialized value. 82 * @origin: Stack ID of the uninitialized value. 83 * @address: Address at which the memory access happens. 84 * @size: Memory access size. 85 * @off_first: Offset (from @address) of the first byte to be reported. 86 * @off_last: Offset (from @address) of the last byte to be reported. 87 * @user_addr: When non-NULL, denotes the userspace address to which the kernel 88 * is leaking data. 89 * @reason: Error type from enum kmsan_bug_reason. 90 * 91 * kmsan_report() prints an error message for a consequent group of bytes 92 * sharing the same origin. If an uninitialized value is used in a comparison, 93 * this function is called once without specifying the addresses. When checking 94 * a memory range, KMSAN may call kmsan_report() multiple times with the same 95 * @address, @size, @user_addr and @reason, but different @off_first and 96 * @off_last corresponding to different @origin values. 97 */ 98 void kmsan_report(depot_stack_handle_t origin, void *address, int size, 99 int off_first, int off_last, const void *user_addr, 100 enum kmsan_bug_reason reason); 101 102 DECLARE_PER_CPU(struct kmsan_ctx, kmsan_percpu_ctx); 103 104 static __always_inline struct kmsan_ctx *kmsan_get_context(void) 105 { 106 return in_task() ? ¤t->kmsan_ctx : raw_cpu_ptr(&kmsan_percpu_ctx); 107 } 108 109 /* 110 * When a compiler hook or KMSAN runtime function is invoked, it may make a 111 * call to instrumented code and eventually call itself recursively. To avoid 112 * that, we guard the runtime entry regions with 113 * kmsan_enter_runtime()/kmsan_leave_runtime() and exit the hook if 114 * kmsan_in_runtime() is true. 115 * 116 * Non-runtime code may occasionally get executed in nested IRQs from the 117 * runtime code (e.g. when called via smp_call_function_single()). Because some 118 * KMSAN routines may take locks (e.g. for memory allocation), we conservatively 119 * bail out instead of calling them. To minimize the effect of this (potentially 120 * missing initialization events) kmsan_in_runtime() is not checked in 121 * non-blocking runtime functions. 122 */ 123 static __always_inline bool kmsan_in_runtime(void) 124 { 125 if ((hardirq_count() >> HARDIRQ_SHIFT) > 1) 126 return true; 127 if (in_nmi()) 128 return true; 129 return kmsan_get_context()->kmsan_in_runtime; 130 } 131 132 static __always_inline void kmsan_enter_runtime(void) 133 { 134 struct kmsan_ctx *ctx; 135 136 ctx = kmsan_get_context(); 137 KMSAN_WARN_ON(ctx->kmsan_in_runtime++); 138 } 139 140 static __always_inline void kmsan_leave_runtime(void) 141 { 142 struct kmsan_ctx *ctx = kmsan_get_context(); 143 144 KMSAN_WARN_ON(--ctx->kmsan_in_runtime); 145 } 146 147 depot_stack_handle_t kmsan_save_stack(void); 148 depot_stack_handle_t kmsan_save_stack_with_flags(gfp_t flags, 149 unsigned int extra_bits); 150 151 /* 152 * Pack and unpack the origin chain depth and UAF flag to/from the extra bits 153 * provided by the stack depot. 154 * The UAF flag is stored in the lowest bit, followed by the depth in the upper 155 * bits. 156 * set_dsh_extra_bits() is responsible for clamping the value. 157 */ 158 static __always_inline unsigned int kmsan_extra_bits(unsigned int depth, 159 bool uaf) 160 { 161 return (depth << 1) | uaf; 162 } 163 164 static __always_inline bool kmsan_uaf_from_eb(unsigned int extra_bits) 165 { 166 return extra_bits & 1; 167 } 168 169 static __always_inline unsigned int kmsan_depth_from_eb(unsigned int extra_bits) 170 { 171 return extra_bits >> 1; 172 } 173 174 /* 175 * kmsan_internal_ functions are supposed to be very simple and not require the 176 * kmsan_in_runtime() checks. 177 */ 178 void kmsan_internal_memmove_metadata(void *dst, void *src, size_t n); 179 void kmsan_internal_poison_memory(void *address, size_t size, gfp_t flags, 180 unsigned int poison_flags); 181 void kmsan_internal_unpoison_memory(void *address, size_t size, bool checked); 182 void kmsan_internal_set_shadow_origin(void *address, size_t size, int b, 183 u32 origin, bool checked); 184 depot_stack_handle_t kmsan_internal_chain_origin(depot_stack_handle_t id); 185 186 void kmsan_internal_task_create(struct task_struct *task); 187 188 bool kmsan_metadata_is_contiguous(void *addr, size_t size); 189 void kmsan_internal_check_memory(void *addr, size_t size, const void *user_addr, 190 int reason); 191 192 struct page *kmsan_vmalloc_to_page_or_null(void *vaddr); 193 void kmsan_setup_meta(struct page *page, struct page *shadow, 194 struct page *origin, int order); 195 196 /* 197 * kmsan_internal_is_module_addr() and kmsan_internal_is_vmalloc_addr() are 198 * non-instrumented versions of is_module_address() and is_vmalloc_addr() that 199 * are safe to call from KMSAN runtime without recursion. 200 */ 201 static inline bool kmsan_internal_is_module_addr(void *vaddr) 202 { 203 return ((u64)vaddr >= MODULES_VADDR) && ((u64)vaddr < MODULES_END); 204 } 205 206 static inline bool kmsan_internal_is_vmalloc_addr(void *addr) 207 { 208 return ((u64)addr >= VMALLOC_START) && ((u64)addr < VMALLOC_END); 209 } 210 211 #endif /* __MM_KMSAN_KMSAN_H */ 212