xref: /openbmc/linux/lib/ubsan.c (revision cc8bbe1a)
1 /*
2  * UBSAN error reporting functions
3  *
4  * Copyright (c) 2014 Samsung Electronics Co., Ltd.
5  * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
6  *
7  * This program is free software; you can redistribute it and/or modify
8  * it under the terms of the GNU General Public License version 2 as
9  * published by the Free Software Foundation.
10  *
11  */
12 
13 #include <linux/bitops.h>
14 #include <linux/bug.h>
15 #include <linux/ctype.h>
16 #include <linux/init.h>
17 #include <linux/kernel.h>
18 #include <linux/types.h>
19 #include <linux/sched.h>
20 
21 #include "ubsan.h"
22 
23 const char *type_check_kinds[] = {
24 	"load of",
25 	"store to",
26 	"reference binding to",
27 	"member access within",
28 	"member call on",
29 	"constructor call on",
30 	"downcast of",
31 	"downcast of"
32 };
33 
34 #define REPORTED_BIT 31
35 
36 #if (BITS_PER_LONG == 64) && defined(__BIG_ENDIAN)
37 #define COLUMN_MASK (~(1U << REPORTED_BIT))
38 #define LINE_MASK   (~0U)
39 #else
40 #define COLUMN_MASK   (~0U)
41 #define LINE_MASK (~(1U << REPORTED_BIT))
42 #endif
43 
44 #define VALUE_LENGTH 40
45 
46 static bool was_reported(struct source_location *location)
47 {
48 	return test_and_set_bit(REPORTED_BIT, &location->reported);
49 }
50 
51 static void print_source_location(const char *prefix,
52 				struct source_location *loc)
53 {
54 	pr_err("%s %s:%d:%d\n", prefix, loc->file_name,
55 		loc->line & LINE_MASK, loc->column & COLUMN_MASK);
56 }
57 
58 static bool suppress_report(struct source_location *loc)
59 {
60 	return current->in_ubsan || was_reported(loc);
61 }
62 
63 static bool type_is_int(struct type_descriptor *type)
64 {
65 	return type->type_kind == type_kind_int;
66 }
67 
68 static bool type_is_signed(struct type_descriptor *type)
69 {
70 	WARN_ON(!type_is_int(type));
71 	return  type->type_info & 1;
72 }
73 
74 static unsigned type_bit_width(struct type_descriptor *type)
75 {
76 	return 1 << (type->type_info >> 1);
77 }
78 
79 static bool is_inline_int(struct type_descriptor *type)
80 {
81 	unsigned inline_bits = sizeof(unsigned long)*8;
82 	unsigned bits = type_bit_width(type);
83 
84 	WARN_ON(!type_is_int(type));
85 
86 	return bits <= inline_bits;
87 }
88 
89 static s_max get_signed_val(struct type_descriptor *type, unsigned long val)
90 {
91 	if (is_inline_int(type)) {
92 		unsigned extra_bits = sizeof(s_max)*8 - type_bit_width(type);
93 		return ((s_max)val) << extra_bits >> extra_bits;
94 	}
95 
96 	if (type_bit_width(type) == 64)
97 		return *(s64 *)val;
98 
99 	return *(s_max *)val;
100 }
101 
102 static bool val_is_negative(struct type_descriptor *type, unsigned long val)
103 {
104 	return type_is_signed(type) && get_signed_val(type, val) < 0;
105 }
106 
107 static u_max get_unsigned_val(struct type_descriptor *type, unsigned long val)
108 {
109 	if (is_inline_int(type))
110 		return val;
111 
112 	if (type_bit_width(type) == 64)
113 		return *(u64 *)val;
114 
115 	return *(u_max *)val;
116 }
117 
118 static void val_to_string(char *str, size_t size, struct type_descriptor *type,
119 	unsigned long value)
120 {
121 	if (type_is_int(type)) {
122 		if (type_bit_width(type) == 128) {
123 #if defined(CONFIG_ARCH_SUPPORTS_INT128) && defined(__SIZEOF_INT128__)
124 			u_max val = get_unsigned_val(type, value);
125 
126 			scnprintf(str, size, "0x%08x%08x%08x%08x",
127 				(u32)(val >> 96),
128 				(u32)(val >> 64),
129 				(u32)(val >> 32),
130 				(u32)(val));
131 #else
132 			WARN_ON(1);
133 #endif
134 		} else if (type_is_signed(type)) {
135 			scnprintf(str, size, "%lld",
136 				(s64)get_signed_val(type, value));
137 		} else {
138 			scnprintf(str, size, "%llu",
139 				(u64)get_unsigned_val(type, value));
140 		}
141 	}
142 }
143 
144 static bool location_is_valid(struct source_location *loc)
145 {
146 	return loc->file_name != NULL;
147 }
148 
149 static DEFINE_SPINLOCK(report_lock);
150 
151 static void ubsan_prologue(struct source_location *location,
152 			unsigned long *flags)
153 {
154 	current->in_ubsan++;
155 	spin_lock_irqsave(&report_lock, *flags);
156 
157 	pr_err("========================================"
158 		"========================================\n");
159 	print_source_location("UBSAN: Undefined behaviour in", location);
160 }
161 
162 static void ubsan_epilogue(unsigned long *flags)
163 {
164 	dump_stack();
165 	pr_err("========================================"
166 		"========================================\n");
167 	spin_unlock_irqrestore(&report_lock, *flags);
168 	current->in_ubsan--;
169 }
170 
171 static void handle_overflow(struct overflow_data *data, unsigned long lhs,
172 			unsigned long rhs, char op)
173 {
174 
175 	struct type_descriptor *type = data->type;
176 	unsigned long flags;
177 	char lhs_val_str[VALUE_LENGTH];
178 	char rhs_val_str[VALUE_LENGTH];
179 
180 	if (suppress_report(&data->location))
181 		return;
182 
183 	ubsan_prologue(&data->location, &flags);
184 
185 	val_to_string(lhs_val_str, sizeof(lhs_val_str), type, lhs);
186 	val_to_string(rhs_val_str, sizeof(rhs_val_str), type, rhs);
187 	pr_err("%s integer overflow:\n",
188 		type_is_signed(type) ? "signed" : "unsigned");
189 	pr_err("%s %c %s cannot be represented in type %s\n",
190 		lhs_val_str,
191 		op,
192 		rhs_val_str,
193 		type->type_name);
194 
195 	ubsan_epilogue(&flags);
196 }
197 
198 void __ubsan_handle_add_overflow(struct overflow_data *data,
199 				unsigned long lhs,
200 				unsigned long rhs)
201 {
202 
203 	handle_overflow(data, lhs, rhs, '+');
204 }
205 EXPORT_SYMBOL(__ubsan_handle_add_overflow);
206 
207 void __ubsan_handle_sub_overflow(struct overflow_data *data,
208 				unsigned long lhs,
209 				unsigned long rhs)
210 {
211 	handle_overflow(data, lhs, rhs, '-');
212 }
213 EXPORT_SYMBOL(__ubsan_handle_sub_overflow);
214 
215 void __ubsan_handle_mul_overflow(struct overflow_data *data,
216 				unsigned long lhs,
217 				unsigned long rhs)
218 {
219 	handle_overflow(data, lhs, rhs, '*');
220 }
221 EXPORT_SYMBOL(__ubsan_handle_mul_overflow);
222 
223 void __ubsan_handle_negate_overflow(struct overflow_data *data,
224 				unsigned long old_val)
225 {
226 	unsigned long flags;
227 	char old_val_str[VALUE_LENGTH];
228 
229 	if (suppress_report(&data->location))
230 		return;
231 
232 	ubsan_prologue(&data->location, &flags);
233 
234 	val_to_string(old_val_str, sizeof(old_val_str), data->type, old_val);
235 
236 	pr_err("negation of %s cannot be represented in type %s:\n",
237 		old_val_str, data->type->type_name);
238 
239 	ubsan_epilogue(&flags);
240 }
241 EXPORT_SYMBOL(__ubsan_handle_negate_overflow);
242 
243 
244 void __ubsan_handle_divrem_overflow(struct overflow_data *data,
245 				unsigned long lhs,
246 				unsigned long rhs)
247 {
248 	unsigned long flags;
249 	char rhs_val_str[VALUE_LENGTH];
250 
251 	if (suppress_report(&data->location))
252 		return;
253 
254 	ubsan_prologue(&data->location, &flags);
255 
256 	val_to_string(rhs_val_str, sizeof(rhs_val_str), data->type, rhs);
257 
258 	if (type_is_signed(data->type) && get_signed_val(data->type, rhs) == -1)
259 		pr_err("division of %s by -1 cannot be represented in type %s\n",
260 			rhs_val_str, data->type->type_name);
261 	else
262 		pr_err("division by zero\n");
263 
264 	ubsan_epilogue(&flags);
265 }
266 EXPORT_SYMBOL(__ubsan_handle_divrem_overflow);
267 
268 static void handle_null_ptr_deref(struct type_mismatch_data *data)
269 {
270 	unsigned long flags;
271 
272 	if (suppress_report(&data->location))
273 		return;
274 
275 	ubsan_prologue(&data->location, &flags);
276 
277 	pr_err("%s null pointer of type %s\n",
278 		type_check_kinds[data->type_check_kind],
279 		data->type->type_name);
280 
281 	ubsan_epilogue(&flags);
282 }
283 
284 static void handle_missaligned_access(struct type_mismatch_data *data,
285 				unsigned long ptr)
286 {
287 	unsigned long flags;
288 
289 	if (suppress_report(&data->location))
290 		return;
291 
292 	ubsan_prologue(&data->location, &flags);
293 
294 	pr_err("%s misaligned address %p for type %s\n",
295 		type_check_kinds[data->type_check_kind],
296 		(void *)ptr, data->type->type_name);
297 	pr_err("which requires %ld byte alignment\n", data->alignment);
298 
299 	ubsan_epilogue(&flags);
300 }
301 
302 static void handle_object_size_mismatch(struct type_mismatch_data *data,
303 					unsigned long ptr)
304 {
305 	unsigned long flags;
306 
307 	if (suppress_report(&data->location))
308 		return;
309 
310 	ubsan_prologue(&data->location, &flags);
311 	pr_err("%s address %pk with insufficient space\n",
312 		type_check_kinds[data->type_check_kind],
313 		(void *) ptr);
314 	pr_err("for an object of type %s\n", data->type->type_name);
315 	ubsan_epilogue(&flags);
316 }
317 
318 void __ubsan_handle_type_mismatch(struct type_mismatch_data *data,
319 				unsigned long ptr)
320 {
321 
322 	if (!ptr)
323 		handle_null_ptr_deref(data);
324 	else if (data->alignment && !IS_ALIGNED(ptr, data->alignment))
325 		handle_missaligned_access(data, ptr);
326 	else
327 		handle_object_size_mismatch(data, ptr);
328 }
329 EXPORT_SYMBOL(__ubsan_handle_type_mismatch);
330 
331 void __ubsan_handle_nonnull_return(struct nonnull_return_data *data)
332 {
333 	unsigned long flags;
334 
335 	if (suppress_report(&data->location))
336 		return;
337 
338 	ubsan_prologue(&data->location, &flags);
339 
340 	pr_err("null pointer returned from function declared to never return null\n");
341 
342 	if (location_is_valid(&data->attr_location))
343 		print_source_location("returns_nonnull attribute specified in",
344 				&data->attr_location);
345 
346 	ubsan_epilogue(&flags);
347 }
348 EXPORT_SYMBOL(__ubsan_handle_nonnull_return);
349 
350 void __ubsan_handle_vla_bound_not_positive(struct vla_bound_data *data,
351 					unsigned long bound)
352 {
353 	unsigned long flags;
354 	char bound_str[VALUE_LENGTH];
355 
356 	if (suppress_report(&data->location))
357 		return;
358 
359 	ubsan_prologue(&data->location, &flags);
360 
361 	val_to_string(bound_str, sizeof(bound_str), data->type, bound);
362 	pr_err("variable length array bound value %s <= 0\n", bound_str);
363 
364 	ubsan_epilogue(&flags);
365 }
366 EXPORT_SYMBOL(__ubsan_handle_vla_bound_not_positive);
367 
368 void __ubsan_handle_out_of_bounds(struct out_of_bounds_data *data,
369 				unsigned long index)
370 {
371 	unsigned long flags;
372 	char index_str[VALUE_LENGTH];
373 
374 	if (suppress_report(&data->location))
375 		return;
376 
377 	ubsan_prologue(&data->location, &flags);
378 
379 	val_to_string(index_str, sizeof(index_str), data->index_type, index);
380 	pr_err("index %s is out of range for type %s\n", index_str,
381 		data->array_type->type_name);
382 	ubsan_epilogue(&flags);
383 }
384 EXPORT_SYMBOL(__ubsan_handle_out_of_bounds);
385 
386 void __ubsan_handle_shift_out_of_bounds(struct shift_out_of_bounds_data *data,
387 					unsigned long lhs, unsigned long rhs)
388 {
389 	unsigned long flags;
390 	struct type_descriptor *rhs_type = data->rhs_type;
391 	struct type_descriptor *lhs_type = data->lhs_type;
392 	char rhs_str[VALUE_LENGTH];
393 	char lhs_str[VALUE_LENGTH];
394 
395 	if (suppress_report(&data->location))
396 		return;
397 
398 	ubsan_prologue(&data->location, &flags);
399 
400 	val_to_string(rhs_str, sizeof(rhs_str), rhs_type, rhs);
401 	val_to_string(lhs_str, sizeof(lhs_str), lhs_type, lhs);
402 
403 	if (val_is_negative(rhs_type, rhs))
404 		pr_err("shift exponent %s is negative\n", rhs_str);
405 
406 	else if (get_unsigned_val(rhs_type, rhs) >=
407 		type_bit_width(lhs_type))
408 		pr_err("shift exponent %s is too large for %u-bit type %s\n",
409 			rhs_str,
410 			type_bit_width(lhs_type),
411 			lhs_type->type_name);
412 	else if (val_is_negative(lhs_type, lhs))
413 		pr_err("left shift of negative value %s\n",
414 			lhs_str);
415 	else
416 		pr_err("left shift of %s by %s places cannot be"
417 			" represented in type %s\n",
418 			lhs_str, rhs_str,
419 			lhs_type->type_name);
420 
421 	ubsan_epilogue(&flags);
422 }
423 EXPORT_SYMBOL(__ubsan_handle_shift_out_of_bounds);
424 
425 
426 void __noreturn
427 __ubsan_handle_builtin_unreachable(struct unreachable_data *data)
428 {
429 	unsigned long flags;
430 
431 	ubsan_prologue(&data->location, &flags);
432 	pr_err("calling __builtin_unreachable()\n");
433 	ubsan_epilogue(&flags);
434 	panic("can't return from __builtin_unreachable()");
435 }
436 EXPORT_SYMBOL(__ubsan_handle_builtin_unreachable);
437 
438 void __ubsan_handle_load_invalid_value(struct invalid_value_data *data,
439 				unsigned long val)
440 {
441 	unsigned long flags;
442 	char val_str[VALUE_LENGTH];
443 
444 	if (suppress_report(&data->location))
445 		return;
446 
447 	ubsan_prologue(&data->location, &flags);
448 
449 	val_to_string(val_str, sizeof(val_str), data->type, val);
450 
451 	pr_err("load of value %s is not a valid value for type %s\n",
452 		val_str, data->type->type_name);
453 
454 	ubsan_epilogue(&flags);
455 }
456 EXPORT_SYMBOL(__ubsan_handle_load_invalid_value);
457