xref: /openbmc/linux/lib/ubsan.c (revision 2b91c4a8) 
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * UBSAN error reporting functions
4  *
5  * Copyright (c) 2014 Samsung Electronics Co., Ltd.
6  * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
7  */
8 
9 #include <linux/bitops.h>
10 #include <linux/bug.h>
11 #include <linux/ctype.h>
12 #include <linux/init.h>
13 #include <linux/kernel.h>
14 #include <linux/types.h>
15 #include <linux/sched.h>
16 #include <linux/uaccess.h>
17 #include <linux/ubsan.h>
18 #include <kunit/test-bug.h>
19 
20 #include "ubsan.h"
21 
22 #ifdef CONFIG_UBSAN_TRAP
23 /*
24  * Only include matches for UBSAN checks that are actually compiled in.
25  * The mappings of struct SanitizerKind (the -fsanitize=xxx args) to
26  * enum SanitizerHandler (the traps) in Clang is in clang/lib/CodeGen/.
27  */
28 const char *report_ubsan_failure(struct pt_regs *regs, u32 check_type)
29 {
30 	switch (check_type) {
31 #ifdef CONFIG_UBSAN_BOUNDS
32 	/*
33 	 * SanitizerKind::ArrayBounds and SanitizerKind::LocalBounds
34 	 * emit SanitizerHandler::OutOfBounds.
35 	 */
36 	case ubsan_out_of_bounds:
37 		return "UBSAN: array index out of bounds";
38 #endif
39 #ifdef CONFIG_UBSAN_SHIFT
40 	/*
41 	 * SanitizerKind::ShiftBase and SanitizerKind::ShiftExponent
42 	 * emit SanitizerHandler::ShiftOutOfBounds.
43 	 */
44 	case ubsan_shift_out_of_bounds:
45 		return "UBSAN: shift out of bounds";
46 #endif
47 #ifdef CONFIG_UBSAN_DIV_ZERO
48 	/*
49 	 * SanitizerKind::IntegerDivideByZero emits
50 	 * SanitizerHandler::DivremOverflow.
51 	 */
52 	case ubsan_divrem_overflow:
53 		return "UBSAN: divide/remainder overflow";
54 #endif
55 #ifdef CONFIG_UBSAN_UNREACHABLE
56 	/*
57 	 * SanitizerKind::Unreachable emits
58 	 * SanitizerHandler::BuiltinUnreachable.
59 	 */
60 	case ubsan_builtin_unreachable:
61 		return "UBSAN: unreachable code";
62 #endif
63 #if defined(CONFIG_UBSAN_BOOL) || defined(CONFIG_UBSAN_ENUM)
64 	/*
65 	 * SanitizerKind::Bool and SanitizerKind::Enum emit
66 	 * SanitizerHandler::LoadInvalidValue.
67 	 */
68 	case ubsan_load_invalid_value:
69 		return "UBSAN: loading invalid value";
70 #endif
71 #ifdef CONFIG_UBSAN_ALIGNMENT
72 	/*
73 	 * SanitizerKind::Alignment emits SanitizerHandler::TypeMismatch
74 	 * or SanitizerHandler::AlignmentAssumption.
75 	 */
76 	case ubsan_alignment_assumption:
77 		return "UBSAN: alignment assumption";
78 	case ubsan_type_mismatch:
79 		return "UBSAN: type mismatch";
80 #endif
81 	default:
82 		return "UBSAN: unrecognized failure code";
83 	}
84 }
85 
86 #else
87 static const char * const type_check_kinds[] = {
88 	"load of",
89 	"store to",
90 	"reference binding to",
91 	"member access within",
92 	"member call on",
93 	"constructor call on",
94 	"downcast of",
95 	"downcast of"
96 };
97 
98 #define REPORTED_BIT 31
99 
100 #if (BITS_PER_LONG == 64) && defined(__BIG_ENDIAN)
101 #define COLUMN_MASK (~(1U << REPORTED_BIT))
102 #define LINE_MASK   (~0U)
103 #else
104 #define COLUMN_MASK   (~0U)
105 #define LINE_MASK (~(1U << REPORTED_BIT))
106 #endif
107 
108 #define VALUE_LENGTH 40
109 
110 static bool was_reported(struct source_location *location)
111 {
112 	return test_and_set_bit(REPORTED_BIT, &location->reported);
113 }
114 
115 static bool suppress_report(struct source_location *loc)
116 {
117 	return current->in_ubsan || was_reported(loc);
118 }
119 
120 static bool type_is_int(struct type_descriptor *type)
121 {
122 	return type->type_kind == type_kind_int;
123 }
124 
125 static bool type_is_signed(struct type_descriptor *type)
126 {
127 	WARN_ON(!type_is_int(type));
128 	return  type->type_info & 1;
129 }
130 
131 static unsigned type_bit_width(struct type_descriptor *type)
132 {
133 	return 1 << (type->type_info >> 1);
134 }
135 
136 static bool is_inline_int(struct type_descriptor *type)
137 {
138 	unsigned inline_bits = sizeof(unsigned long)*8;
139 	unsigned bits = type_bit_width(type);
140 
141 	WARN_ON(!type_is_int(type));
142 
143 	return bits <= inline_bits;
144 }
145 
146 static s_max get_signed_val(struct type_descriptor *type, void *val)
147 {
148 	if (is_inline_int(type)) {
149 		unsigned extra_bits = sizeof(s_max)*8 - type_bit_width(type);
150 		unsigned long ulong_val = (unsigned long)val;
151 
152 		return ((s_max)ulong_val) << extra_bits >> extra_bits;
153 	}
154 
155 	if (type_bit_width(type) == 64)
156 		return *(s64 *)val;
157 
158 	return *(s_max *)val;
159 }
160 
161 static bool val_is_negative(struct type_descriptor *type, void *val)
162 {
163 	return type_is_signed(type) && get_signed_val(type, val) < 0;
164 }
165 
166 static u_max get_unsigned_val(struct type_descriptor *type, void *val)
167 {
168 	if (is_inline_int(type))
169 		return (unsigned long)val;
170 
171 	if (type_bit_width(type) == 64)
172 		return *(u64 *)val;
173 
174 	return *(u_max *)val;
175 }
176 
177 static void val_to_string(char *str, size_t size, struct type_descriptor *type,
178 			void *value)
179 {
180 	if (type_is_int(type)) {
181 		if (type_bit_width(type) == 128) {
182 #if defined(CONFIG_ARCH_SUPPORTS_INT128)
183 			u_max val = get_unsigned_val(type, value);
184 
185 			scnprintf(str, size, "0x%08x%08x%08x%08x",
186 				(u32)(val >> 96),
187 				(u32)(val >> 64),
188 				(u32)(val >> 32),
189 				(u32)(val));
190 #else
191 			WARN_ON(1);
192 #endif
193 		} else if (type_is_signed(type)) {
194 			scnprintf(str, size, "%lld",
195 				(s64)get_signed_val(type, value));
196 		} else {
197 			scnprintf(str, size, "%llu",
198 				(u64)get_unsigned_val(type, value));
199 		}
200 	}
201 }
202 
203 static void ubsan_prologue(struct source_location *loc, const char *reason)
204 {
205 	current->in_ubsan++;
206 
207 	pr_err("========================================"
208 		"========================================\n");
209 	pr_err("UBSAN: %s in %s:%d:%d\n", reason, loc->file_name,
210 		loc->line & LINE_MASK, loc->column & COLUMN_MASK);
211 
212 	kunit_fail_current_test("%s in %s", reason, loc->file_name);
213 }
214 
215 static void ubsan_epilogue(void)
216 {
217 	dump_stack();
218 	pr_err("========================================"
219 		"========================================\n");
220 
221 	current->in_ubsan--;
222 
223 	check_panic_on_warn("UBSAN");
224 }
225 
226 void __ubsan_handle_divrem_overflow(void *_data, void *lhs, void *rhs)
227 {
228 	struct overflow_data *data = _data;
229 	char rhs_val_str[VALUE_LENGTH];
230 
231 	if (suppress_report(&data->location))
232 		return;
233 
234 	ubsan_prologue(&data->location, "division-overflow");
235 
236 	val_to_string(rhs_val_str, sizeof(rhs_val_str), data->type, rhs);
237 
238 	if (type_is_signed(data->type) && get_signed_val(data->type, rhs) == -1)
239 		pr_err("division of %s by -1 cannot be represented in type %s\n",
240 			rhs_val_str, data->type->type_name);
241 	else
242 		pr_err("division by zero\n");
243 
244 	ubsan_epilogue();
245 }
246 EXPORT_SYMBOL(__ubsan_handle_divrem_overflow);
247 
248 static void handle_null_ptr_deref(struct type_mismatch_data_common *data)
249 {
250 	if (suppress_report(data->location))
251 		return;
252 
253 	ubsan_prologue(data->location, "null-ptr-deref");
254 
255 	pr_err("%s null pointer of type %s\n",
256 		type_check_kinds[data->type_check_kind],
257 		data->type->type_name);
258 
259 	ubsan_epilogue();
260 }
261 
262 static void handle_misaligned_access(struct type_mismatch_data_common *data,
263 				unsigned long ptr)
264 {
265 	if (suppress_report(data->location))
266 		return;
267 
268 	ubsan_prologue(data->location, "misaligned-access");
269 
270 	pr_err("%s misaligned address %p for type %s\n",
271 		type_check_kinds[data->type_check_kind],
272 		(void *)ptr, data->type->type_name);
273 	pr_err("which requires %ld byte alignment\n", data->alignment);
274 
275 	ubsan_epilogue();
276 }
277 
278 static void handle_object_size_mismatch(struct type_mismatch_data_common *data,
279 					unsigned long ptr)
280 {
281 	if (suppress_report(data->location))
282 		return;
283 
284 	ubsan_prologue(data->location, "object-size-mismatch");
285 	pr_err("%s address %p with insufficient space\n",
286 		type_check_kinds[data->type_check_kind],
287 		(void *) ptr);
288 	pr_err("for an object of type %s\n", data->type->type_name);
289 	ubsan_epilogue();
290 }
291 
292 static void ubsan_type_mismatch_common(struct type_mismatch_data_common *data,
293 				unsigned long ptr)
294 {
295 	unsigned long flags = user_access_save();
296 
297 	if (!ptr)
298 		handle_null_ptr_deref(data);
299 	else if (data->alignment && !IS_ALIGNED(ptr, data->alignment))
300 		handle_misaligned_access(data, ptr);
301 	else
302 		handle_object_size_mismatch(data, ptr);
303 
304 	user_access_restore(flags);
305 }
306 
307 void __ubsan_handle_type_mismatch(struct type_mismatch_data *data,
308 				void *ptr)
309 {
310 	struct type_mismatch_data_common common_data = {
311 		.location = &data->location,
312 		.type = data->type,
313 		.alignment = data->alignment,
314 		.type_check_kind = data->type_check_kind
315 	};
316 
317 	ubsan_type_mismatch_common(&common_data, (unsigned long)ptr);
318 }
319 EXPORT_SYMBOL(__ubsan_handle_type_mismatch);
320 
321 void __ubsan_handle_type_mismatch_v1(void *_data, void *ptr)
322 {
323 	struct type_mismatch_data_v1 *data = _data;
324 	struct type_mismatch_data_common common_data = {
325 		.location = &data->location,
326 		.type = data->type,
327 		.alignment = 1UL << data->log_alignment,
328 		.type_check_kind = data->type_check_kind
329 	};
330 
331 	ubsan_type_mismatch_common(&common_data, (unsigned long)ptr);
332 }
333 EXPORT_SYMBOL(__ubsan_handle_type_mismatch_v1);
334 
335 void __ubsan_handle_out_of_bounds(void *_data, void *index)
336 {
337 	struct out_of_bounds_data *data = _data;
338 	char index_str[VALUE_LENGTH];
339 
340 	if (suppress_report(&data->location))
341 		return;
342 
343 	ubsan_prologue(&data->location, "array-index-out-of-bounds");
344 
345 	val_to_string(index_str, sizeof(index_str), data->index_type, index);
346 	pr_err("index %s is out of range for type %s\n", index_str,
347 		data->array_type->type_name);
348 	ubsan_epilogue();
349 }
350 EXPORT_SYMBOL(__ubsan_handle_out_of_bounds);
351 
352 void __ubsan_handle_shift_out_of_bounds(void *_data, void *lhs, void *rhs)
353 {
354 	struct shift_out_of_bounds_data *data = _data;
355 	struct type_descriptor *rhs_type = data->rhs_type;
356 	struct type_descriptor *lhs_type = data->lhs_type;
357 	char rhs_str[VALUE_LENGTH];
358 	char lhs_str[VALUE_LENGTH];
359 	unsigned long ua_flags = user_access_save();
360 
361 	if (suppress_report(&data->location))
362 		goto out;
363 
364 	ubsan_prologue(&data->location, "shift-out-of-bounds");
365 
366 	val_to_string(rhs_str, sizeof(rhs_str), rhs_type, rhs);
367 	val_to_string(lhs_str, sizeof(lhs_str), lhs_type, lhs);
368 
369 	if (val_is_negative(rhs_type, rhs))
370 		pr_err("shift exponent %s is negative\n", rhs_str);
371 
372 	else if (get_unsigned_val(rhs_type, rhs) >=
373 		type_bit_width(lhs_type))
374 		pr_err("shift exponent %s is too large for %u-bit type %s\n",
375 			rhs_str,
376 			type_bit_width(lhs_type),
377 			lhs_type->type_name);
378 	else if (val_is_negative(lhs_type, lhs))
379 		pr_err("left shift of negative value %s\n",
380 			lhs_str);
381 	else
382 		pr_err("left shift of %s by %s places cannot be"
383 			" represented in type %s\n",
384 			lhs_str, rhs_str,
385 			lhs_type->type_name);
386 
387 	ubsan_epilogue();
388 out:
389 	user_access_restore(ua_flags);
390 }
391 EXPORT_SYMBOL(__ubsan_handle_shift_out_of_bounds);
392 
393 
394 void __ubsan_handle_builtin_unreachable(void *_data)
395 {
396 	struct unreachable_data *data = _data;
397 	ubsan_prologue(&data->location, "unreachable");
398 	pr_err("calling __builtin_unreachable()\n");
399 	ubsan_epilogue();
400 	panic("can't return from __builtin_unreachable()");
401 }
402 EXPORT_SYMBOL(__ubsan_handle_builtin_unreachable);
403 
404 void __ubsan_handle_load_invalid_value(void *_data, void *val)
405 {
406 	struct invalid_value_data *data = _data;
407 	char val_str[VALUE_LENGTH];
408 	unsigned long ua_flags = user_access_save();
409 
410 	if (suppress_report(&data->location))
411 		goto out;
412 
413 	ubsan_prologue(&data->location, "invalid-load");
414 
415 	val_to_string(val_str, sizeof(val_str), data->type, val);
416 
417 	pr_err("load of value %s is not a valid value for type %s\n",
418 		val_str, data->type->type_name);
419 
420 	ubsan_epilogue();
421 out:
422 	user_access_restore(ua_flags);
423 }
424 EXPORT_SYMBOL(__ubsan_handle_load_invalid_value);
425 
426 void __ubsan_handle_alignment_assumption(void *_data, unsigned long ptr,
427 					 unsigned long align,
428 					 unsigned long offset);
429 void __ubsan_handle_alignment_assumption(void *_data, unsigned long ptr,
430 					 unsigned long align,
431 					 unsigned long offset)
432 {
433 	struct alignment_assumption_data *data = _data;
434 	unsigned long real_ptr;
435 
436 	if (suppress_report(&data->location))
437 		return;
438 
439 	ubsan_prologue(&data->location, "alignment-assumption");
440 
441 	if (offset)
442 		pr_err("assumption of %lu byte alignment (with offset of %lu byte) for pointer of type %s failed",
443 		       align, offset, data->type->type_name);
444 	else
445 		pr_err("assumption of %lu byte alignment for pointer of type %s failed",
446 		       align, data->type->type_name);
447 
448 	real_ptr = ptr - offset;
449 	pr_err("%saddress is %lu aligned, misalignment offset is %lu bytes",
450 	       offset ? "offset " : "", BIT(real_ptr ? __ffs(real_ptr) : 0),
451 	       real_ptr & (align - 1));
452 
453 	ubsan_epilogue();
454 }
455 EXPORT_SYMBOL(__ubsan_handle_alignment_assumption);
456 
457 #endif /* !CONFIG_UBSAN_TRAP */
458