xref: /linux/lib/ubsan.c (revision 4b660dbd9ee2059850fd30e0df420ca7a38a1856) 
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_warn(CUT_HERE);
208 
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_warn("---[ end trace ]---\n");
219 
220 	current->in_ubsan--;
221 
222 	check_panic_on_warn("UBSAN");
223 }
224 
225 static void handle_overflow(struct overflow_data *data, void *lhs,
226 			void *rhs, char op)
227 {
228 
229 	struct type_descriptor *type = data->type;
230 	char lhs_val_str[VALUE_LENGTH];
231 	char rhs_val_str[VALUE_LENGTH];
232 
233 	if (suppress_report(&data->location))
234 		return;
235 
236 	ubsan_prologue(&data->location, type_is_signed(type) ?
237 			"signed-integer-overflow" :
238 			"unsigned-integer-overflow");
239 
240 	val_to_string(lhs_val_str, sizeof(lhs_val_str), type, lhs);
241 	val_to_string(rhs_val_str, sizeof(rhs_val_str), type, rhs);
242 	pr_err("%s %c %s cannot be represented in type %s\n",
243 		lhs_val_str,
244 		op,
245 		rhs_val_str,
246 		type->type_name);
247 
248 	ubsan_epilogue();
249 }
250 
251 void __ubsan_handle_add_overflow(void *data,
252 				void *lhs, void *rhs)
253 {
254 
255 	handle_overflow(data, lhs, rhs, '+');
256 }
257 EXPORT_SYMBOL(__ubsan_handle_add_overflow);
258 
259 void __ubsan_handle_sub_overflow(void *data,
260 				void *lhs, void *rhs)
261 {
262 	handle_overflow(data, lhs, rhs, '-');
263 }
264 EXPORT_SYMBOL(__ubsan_handle_sub_overflow);
265 
266 void __ubsan_handle_mul_overflow(void *data,
267 				void *lhs, void *rhs)
268 {
269 	handle_overflow(data, lhs, rhs, '*');
270 }
271 EXPORT_SYMBOL(__ubsan_handle_mul_overflow);
272 
273 void __ubsan_handle_negate_overflow(void *_data, void *old_val)
274 {
275 	struct overflow_data *data = _data;
276 	char old_val_str[VALUE_LENGTH];
277 
278 	if (suppress_report(&data->location))
279 		return;
280 
281 	ubsan_prologue(&data->location, "negation-overflow");
282 
283 	val_to_string(old_val_str, sizeof(old_val_str), data->type, old_val);
284 
285 	pr_err("negation of %s cannot be represented in type %s:\n",
286 		old_val_str, data->type->type_name);
287 
288 	ubsan_epilogue();
289 }
290 EXPORT_SYMBOL(__ubsan_handle_negate_overflow);
291 
292 
293 void __ubsan_handle_divrem_overflow(void *_data, void *lhs, void *rhs)
294 {
295 	struct overflow_data *data = _data;
296 	char rhs_val_str[VALUE_LENGTH];
297 
298 	if (suppress_report(&data->location))
299 		return;
300 
301 	ubsan_prologue(&data->location, "division-overflow");
302 
303 	val_to_string(rhs_val_str, sizeof(rhs_val_str), data->type, rhs);
304 
305 	if (type_is_signed(data->type) && get_signed_val(data->type, rhs) == -1)
306 		pr_err("division of %s by -1 cannot be represented in type %s\n",
307 			rhs_val_str, data->type->type_name);
308 	else
309 		pr_err("division by zero\n");
310 
311 	ubsan_epilogue();
312 }
313 EXPORT_SYMBOL(__ubsan_handle_divrem_overflow);
314 
315 static void handle_null_ptr_deref(struct type_mismatch_data_common *data)
316 {
317 	if (suppress_report(data->location))
318 		return;
319 
320 	ubsan_prologue(data->location, "null-ptr-deref");
321 
322 	pr_err("%s null pointer of type %s\n",
323 		type_check_kinds[data->type_check_kind],
324 		data->type->type_name);
325 
326 	ubsan_epilogue();
327 }
328 
329 static void handle_misaligned_access(struct type_mismatch_data_common *data,
330 				unsigned long ptr)
331 {
332 	if (suppress_report(data->location))
333 		return;
334 
335 	ubsan_prologue(data->location, "misaligned-access");
336 
337 	pr_err("%s misaligned address %p for type %s\n",
338 		type_check_kinds[data->type_check_kind],
339 		(void *)ptr, data->type->type_name);
340 	pr_err("which requires %ld byte alignment\n", data->alignment);
341 
342 	ubsan_epilogue();
343 }
344 
345 static void handle_object_size_mismatch(struct type_mismatch_data_common *data,
346 					unsigned long ptr)
347 {
348 	if (suppress_report(data->location))
349 		return;
350 
351 	ubsan_prologue(data->location, "object-size-mismatch");
352 	pr_err("%s address %p with insufficient space\n",
353 		type_check_kinds[data->type_check_kind],
354 		(void *) ptr);
355 	pr_err("for an object of type %s\n", data->type->type_name);
356 	ubsan_epilogue();
357 }
358 
359 static void ubsan_type_mismatch_common(struct type_mismatch_data_common *data,
360 				unsigned long ptr)
361 {
362 	unsigned long flags = user_access_save();
363 
364 	if (!ptr)
365 		handle_null_ptr_deref(data);
366 	else if (data->alignment && !IS_ALIGNED(ptr, data->alignment))
367 		handle_misaligned_access(data, ptr);
368 	else
369 		handle_object_size_mismatch(data, ptr);
370 
371 	user_access_restore(flags);
372 }
373 
374 void __ubsan_handle_type_mismatch(struct type_mismatch_data *data,
375 				void *ptr)
376 {
377 	struct type_mismatch_data_common common_data = {
378 		.location = &data->location,
379 		.type = data->type,
380 		.alignment = data->alignment,
381 		.type_check_kind = data->type_check_kind
382 	};
383 
384 	ubsan_type_mismatch_common(&common_data, (unsigned long)ptr);
385 }
386 EXPORT_SYMBOL(__ubsan_handle_type_mismatch);
387 
388 void __ubsan_handle_type_mismatch_v1(void *_data, void *ptr)
389 {
390 	struct type_mismatch_data_v1 *data = _data;
391 	struct type_mismatch_data_common common_data = {
392 		.location = &data->location,
393 		.type = data->type,
394 		.alignment = 1UL << data->log_alignment,
395 		.type_check_kind = data->type_check_kind
396 	};
397 
398 	ubsan_type_mismatch_common(&common_data, (unsigned long)ptr);
399 }
400 EXPORT_SYMBOL(__ubsan_handle_type_mismatch_v1);
401 
402 void __ubsan_handle_out_of_bounds(void *_data, void *index)
403 {
404 	struct out_of_bounds_data *data = _data;
405 	char index_str[VALUE_LENGTH];
406 
407 	if (suppress_report(&data->location))
408 		return;
409 
410 	ubsan_prologue(&data->location, "array-index-out-of-bounds");
411 
412 	val_to_string(index_str, sizeof(index_str), data->index_type, index);
413 	pr_err("index %s is out of range for type %s\n", index_str,
414 		data->array_type->type_name);
415 	ubsan_epilogue();
416 }
417 EXPORT_SYMBOL(__ubsan_handle_out_of_bounds);
418 
419 void __ubsan_handle_shift_out_of_bounds(void *_data, void *lhs, void *rhs)
420 {
421 	struct shift_out_of_bounds_data *data = _data;
422 	struct type_descriptor *rhs_type = data->rhs_type;
423 	struct type_descriptor *lhs_type = data->lhs_type;
424 	char rhs_str[VALUE_LENGTH];
425 	char lhs_str[VALUE_LENGTH];
426 	unsigned long ua_flags = user_access_save();
427 
428 	if (suppress_report(&data->location))
429 		goto out;
430 
431 	ubsan_prologue(&data->location, "shift-out-of-bounds");
432 
433 	val_to_string(rhs_str, sizeof(rhs_str), rhs_type, rhs);
434 	val_to_string(lhs_str, sizeof(lhs_str), lhs_type, lhs);
435 
436 	if (val_is_negative(rhs_type, rhs))
437 		pr_err("shift exponent %s is negative\n", rhs_str);
438 
439 	else if (get_unsigned_val(rhs_type, rhs) >=
440 		type_bit_width(lhs_type))
441 		pr_err("shift exponent %s is too large for %u-bit type %s\n",
442 			rhs_str,
443 			type_bit_width(lhs_type),
444 			lhs_type->type_name);
445 	else if (val_is_negative(lhs_type, lhs))
446 		pr_err("left shift of negative value %s\n",
447 			lhs_str);
448 	else
449 		pr_err("left shift of %s by %s places cannot be"
450 			" represented in type %s\n",
451 			lhs_str, rhs_str,
452 			lhs_type->type_name);
453 
454 	ubsan_epilogue();
455 out:
456 	user_access_restore(ua_flags);
457 }
458 EXPORT_SYMBOL(__ubsan_handle_shift_out_of_bounds);
459 
460 
461 void __ubsan_handle_builtin_unreachable(void *_data)
462 {
463 	struct unreachable_data *data = _data;
464 	ubsan_prologue(&data->location, "unreachable");
465 	pr_err("calling __builtin_unreachable()\n");
466 	ubsan_epilogue();
467 	panic("can't return from __builtin_unreachable()");
468 }
469 EXPORT_SYMBOL(__ubsan_handle_builtin_unreachable);
470 
471 void __ubsan_handle_load_invalid_value(void *_data, void *val)
472 {
473 	struct invalid_value_data *data = _data;
474 	char val_str[VALUE_LENGTH];
475 	unsigned long ua_flags = user_access_save();
476 
477 	if (suppress_report(&data->location))
478 		goto out;
479 
480 	ubsan_prologue(&data->location, "invalid-load");
481 
482 	val_to_string(val_str, sizeof(val_str), data->type, val);
483 
484 	pr_err("load of value %s is not a valid value for type %s\n",
485 		val_str, data->type->type_name);
486 
487 	ubsan_epilogue();
488 out:
489 	user_access_restore(ua_flags);
490 }
491 EXPORT_SYMBOL(__ubsan_handle_load_invalid_value);
492 
493 void __ubsan_handle_alignment_assumption(void *_data, unsigned long ptr,
494 					 unsigned long align,
495 					 unsigned long offset)
496 {
497 	struct alignment_assumption_data *data = _data;
498 	unsigned long real_ptr;
499 
500 	if (suppress_report(&data->location))
501 		return;
502 
503 	ubsan_prologue(&data->location, "alignment-assumption");
504 
505 	if (offset)
506 		pr_err("assumption of %lu byte alignment (with offset of %lu byte) for pointer of type %s failed",
507 		       align, offset, data->type->type_name);
508 	else
509 		pr_err("assumption of %lu byte alignment for pointer of type %s failed",
510 		       align, data->type->type_name);
511 
512 	real_ptr = ptr - offset;
513 	pr_err("%saddress is %lu aligned, misalignment offset is %lu bytes",
514 	       offset ? "offset " : "", BIT(real_ptr ? __ffs(real_ptr) : 0),
515 	       real_ptr & (align - 1));
516 
517 	ubsan_epilogue();
518 }
519 EXPORT_SYMBOL(__ubsan_handle_alignment_assumption);
520 
521 #endif /* !CONFIG_UBSAN_TRAP */
522