xref: /linux/lib/ubsan.c (revision 9a6b55ac) 
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 
18 #include "ubsan.h"
19 
20 const char *type_check_kinds[] = {
21 	"load of",
22 	"store to",
23 	"reference binding to",
24 	"member access within",
25 	"member call on",
26 	"constructor call on",
27 	"downcast of",
28 	"downcast of"
29 };
30 
31 #define REPORTED_BIT 31
32 
33 #if (BITS_PER_LONG == 64) && defined(__BIG_ENDIAN)
34 #define COLUMN_MASK (~(1U << REPORTED_BIT))
35 #define LINE_MASK   (~0U)
36 #else
37 #define COLUMN_MASK   (~0U)
38 #define LINE_MASK (~(1U << REPORTED_BIT))
39 #endif
40 
41 #define VALUE_LENGTH 40
42 
43 static bool was_reported(struct source_location *location)
44 {
45 	return test_and_set_bit(REPORTED_BIT, &location->reported);
46 }
47 
48 static void print_source_location(const char *prefix,
49 				struct source_location *loc)
50 {
51 	pr_err("%s %s:%d:%d\n", prefix, loc->file_name,
52 		loc->line & LINE_MASK, loc->column & COLUMN_MASK);
53 }
54 
55 static bool suppress_report(struct source_location *loc)
56 {
57 	return current->in_ubsan || was_reported(loc);
58 }
59 
60 static bool type_is_int(struct type_descriptor *type)
61 {
62 	return type->type_kind == type_kind_int;
63 }
64 
65 static bool type_is_signed(struct type_descriptor *type)
66 {
67 	WARN_ON(!type_is_int(type));
68 	return  type->type_info & 1;
69 }
70 
71 static unsigned type_bit_width(struct type_descriptor *type)
72 {
73 	return 1 << (type->type_info >> 1);
74 }
75 
76 static bool is_inline_int(struct type_descriptor *type)
77 {
78 	unsigned inline_bits = sizeof(unsigned long)*8;
79 	unsigned bits = type_bit_width(type);
80 
81 	WARN_ON(!type_is_int(type));
82 
83 	return bits <= inline_bits;
84 }
85 
86 static s_max get_signed_val(struct type_descriptor *type, void *val)
87 {
88 	if (is_inline_int(type)) {
89 		unsigned extra_bits = sizeof(s_max)*8 - type_bit_width(type);
90 		unsigned long ulong_val = (unsigned long)val;
91 
92 		return ((s_max)ulong_val) << extra_bits >> extra_bits;
93 	}
94 
95 	if (type_bit_width(type) == 64)
96 		return *(s64 *)val;
97 
98 	return *(s_max *)val;
99 }
100 
101 static bool val_is_negative(struct type_descriptor *type, void *val)
102 {
103 	return type_is_signed(type) && get_signed_val(type, val) < 0;
104 }
105 
106 static u_max get_unsigned_val(struct type_descriptor *type, void *val)
107 {
108 	if (is_inline_int(type))
109 		return (unsigned long)val;
110 
111 	if (type_bit_width(type) == 64)
112 		return *(u64 *)val;
113 
114 	return *(u_max *)val;
115 }
116 
117 static void val_to_string(char *str, size_t size, struct type_descriptor *type,
118 			void *value)
119 {
120 	if (type_is_int(type)) {
121 		if (type_bit_width(type) == 128) {
122 #if defined(CONFIG_ARCH_SUPPORTS_INT128)
123 			u_max val = get_unsigned_val(type, value);
124 
125 			scnprintf(str, size, "0x%08x%08x%08x%08x",
126 				(u32)(val >> 96),
127 				(u32)(val >> 64),
128 				(u32)(val >> 32),
129 				(u32)(val));
130 #else
131 			WARN_ON(1);
132 #endif
133 		} else if (type_is_signed(type)) {
134 			scnprintf(str, size, "%lld",
135 				(s64)get_signed_val(type, value));
136 		} else {
137 			scnprintf(str, size, "%llu",
138 				(u64)get_unsigned_val(type, value));
139 		}
140 	}
141 }
142 
143 static void ubsan_prologue(struct source_location *location)
144 {
145 	current->in_ubsan++;
146 
147 	pr_err("========================================"
148 		"========================================\n");
149 	print_source_location("UBSAN: Undefined behaviour in", location);
150 }
151 
152 static void ubsan_epilogue(void)
153 {
154 	dump_stack();
155 	pr_err("========================================"
156 		"========================================\n");
157 
158 	current->in_ubsan--;
159 }
160 
161 static void handle_overflow(struct overflow_data *data, void *lhs,
162 			void *rhs, char op)
163 {
164 
165 	struct type_descriptor *type = data->type;
166 	char lhs_val_str[VALUE_LENGTH];
167 	char rhs_val_str[VALUE_LENGTH];
168 
169 	if (suppress_report(&data->location))
170 		return;
171 
172 	ubsan_prologue(&data->location);
173 
174 	val_to_string(lhs_val_str, sizeof(lhs_val_str), type, lhs);
175 	val_to_string(rhs_val_str, sizeof(rhs_val_str), type, rhs);
176 	pr_err("%s integer overflow:\n",
177 		type_is_signed(type) ? "signed" : "unsigned");
178 	pr_err("%s %c %s cannot be represented in type %s\n",
179 		lhs_val_str,
180 		op,
181 		rhs_val_str,
182 		type->type_name);
183 
184 	ubsan_epilogue();
185 }
186 
187 void __ubsan_handle_add_overflow(struct overflow_data *data,
188 				void *lhs, void *rhs)
189 {
190 
191 	handle_overflow(data, lhs, rhs, '+');
192 }
193 EXPORT_SYMBOL(__ubsan_handle_add_overflow);
194 
195 void __ubsan_handle_sub_overflow(struct overflow_data *data,
196 				void *lhs, void *rhs)
197 {
198 	handle_overflow(data, lhs, rhs, '-');
199 }
200 EXPORT_SYMBOL(__ubsan_handle_sub_overflow);
201 
202 void __ubsan_handle_mul_overflow(struct overflow_data *data,
203 				void *lhs, void *rhs)
204 {
205 	handle_overflow(data, lhs, rhs, '*');
206 }
207 EXPORT_SYMBOL(__ubsan_handle_mul_overflow);
208 
209 void __ubsan_handle_negate_overflow(struct overflow_data *data,
210 				void *old_val)
211 {
212 	char old_val_str[VALUE_LENGTH];
213 
214 	if (suppress_report(&data->location))
215 		return;
216 
217 	ubsan_prologue(&data->location);
218 
219 	val_to_string(old_val_str, sizeof(old_val_str), data->type, old_val);
220 
221 	pr_err("negation of %s cannot be represented in type %s:\n",
222 		old_val_str, data->type->type_name);
223 
224 	ubsan_epilogue();
225 }
226 EXPORT_SYMBOL(__ubsan_handle_negate_overflow);
227 
228 
229 void __ubsan_handle_divrem_overflow(struct overflow_data *data,
230 				void *lhs, void *rhs)
231 {
232 	char rhs_val_str[VALUE_LENGTH];
233 
234 	if (suppress_report(&data->location))
235 		return;
236 
237 	ubsan_prologue(&data->location);
238 
239 	val_to_string(rhs_val_str, sizeof(rhs_val_str), data->type, rhs);
240 
241 	if (type_is_signed(data->type) && get_signed_val(data->type, rhs) == -1)
242 		pr_err("division of %s by -1 cannot be represented in type %s\n",
243 			rhs_val_str, data->type->type_name);
244 	else
245 		pr_err("division by zero\n");
246 
247 	ubsan_epilogue();
248 }
249 EXPORT_SYMBOL(__ubsan_handle_divrem_overflow);
250 
251 static void handle_null_ptr_deref(struct type_mismatch_data_common *data)
252 {
253 	if (suppress_report(data->location))
254 		return;
255 
256 	ubsan_prologue(data->location);
257 
258 	pr_err("%s null pointer of type %s\n",
259 		type_check_kinds[data->type_check_kind],
260 		data->type->type_name);
261 
262 	ubsan_epilogue();
263 }
264 
265 static void handle_misaligned_access(struct type_mismatch_data_common *data,
266 				unsigned long ptr)
267 {
268 	if (suppress_report(data->location))
269 		return;
270 
271 	ubsan_prologue(data->location);
272 
273 	pr_err("%s misaligned address %p for type %s\n",
274 		type_check_kinds[data->type_check_kind],
275 		(void *)ptr, data->type->type_name);
276 	pr_err("which requires %ld byte alignment\n", data->alignment);
277 
278 	ubsan_epilogue();
279 }
280 
281 static void handle_object_size_mismatch(struct type_mismatch_data_common *data,
282 					unsigned long ptr)
283 {
284 	if (suppress_report(data->location))
285 		return;
286 
287 	ubsan_prologue(data->location);
288 	pr_err("%s address %p with insufficient space\n",
289 		type_check_kinds[data->type_check_kind],
290 		(void *) ptr);
291 	pr_err("for an object of type %s\n", data->type->type_name);
292 	ubsan_epilogue();
293 }
294 
295 static void ubsan_type_mismatch_common(struct type_mismatch_data_common *data,
296 				unsigned long ptr)
297 {
298 	unsigned long flags = user_access_save();
299 
300 	if (!ptr)
301 		handle_null_ptr_deref(data);
302 	else if (data->alignment && !IS_ALIGNED(ptr, data->alignment))
303 		handle_misaligned_access(data, ptr);
304 	else
305 		handle_object_size_mismatch(data, ptr);
306 
307 	user_access_restore(flags);
308 }
309 
310 void __ubsan_handle_type_mismatch(struct type_mismatch_data *data,
311 				void *ptr)
312 {
313 	struct type_mismatch_data_common common_data = {
314 		.location = &data->location,
315 		.type = data->type,
316 		.alignment = data->alignment,
317 		.type_check_kind = data->type_check_kind
318 	};
319 
320 	ubsan_type_mismatch_common(&common_data, (unsigned long)ptr);
321 }
322 EXPORT_SYMBOL(__ubsan_handle_type_mismatch);
323 
324 void __ubsan_handle_type_mismatch_v1(struct type_mismatch_data_v1 *data,
325 				void *ptr)
326 {
327 
328 	struct type_mismatch_data_common common_data = {
329 		.location = &data->location,
330 		.type = data->type,
331 		.alignment = 1UL << data->log_alignment,
332 		.type_check_kind = data->type_check_kind
333 	};
334 
335 	ubsan_type_mismatch_common(&common_data, (unsigned long)ptr);
336 }
337 EXPORT_SYMBOL(__ubsan_handle_type_mismatch_v1);
338 
339 void __ubsan_handle_out_of_bounds(struct out_of_bounds_data *data, void *index)
340 {
341 	char index_str[VALUE_LENGTH];
342 
343 	if (suppress_report(&data->location))
344 		return;
345 
346 	ubsan_prologue(&data->location);
347 
348 	val_to_string(index_str, sizeof(index_str), data->index_type, index);
349 	pr_err("index %s is out of range for type %s\n", index_str,
350 		data->array_type->type_name);
351 	ubsan_epilogue();
352 }
353 EXPORT_SYMBOL(__ubsan_handle_out_of_bounds);
354 
355 void __ubsan_handle_shift_out_of_bounds(struct shift_out_of_bounds_data *data,
356 					void *lhs, void *rhs)
357 {
358 	struct type_descriptor *rhs_type = data->rhs_type;
359 	struct type_descriptor *lhs_type = data->lhs_type;
360 	char rhs_str[VALUE_LENGTH];
361 	char lhs_str[VALUE_LENGTH];
362 	unsigned long ua_flags = user_access_save();
363 
364 	if (suppress_report(&data->location))
365 		goto out;
366 
367 	ubsan_prologue(&data->location);
368 
369 	val_to_string(rhs_str, sizeof(rhs_str), rhs_type, rhs);
370 	val_to_string(lhs_str, sizeof(lhs_str), lhs_type, lhs);
371 
372 	if (val_is_negative(rhs_type, rhs))
373 		pr_err("shift exponent %s is negative\n", rhs_str);
374 
375 	else if (get_unsigned_val(rhs_type, rhs) >=
376 		type_bit_width(lhs_type))
377 		pr_err("shift exponent %s is too large for %u-bit type %s\n",
378 			rhs_str,
379 			type_bit_width(lhs_type),
380 			lhs_type->type_name);
381 	else if (val_is_negative(lhs_type, lhs))
382 		pr_err("left shift of negative value %s\n",
383 			lhs_str);
384 	else
385 		pr_err("left shift of %s by %s places cannot be"
386 			" represented in type %s\n",
387 			lhs_str, rhs_str,
388 			lhs_type->type_name);
389 
390 	ubsan_epilogue();
391 out:
392 	user_access_restore(ua_flags);
393 }
394 EXPORT_SYMBOL(__ubsan_handle_shift_out_of_bounds);
395 
396 
397 void __ubsan_handle_builtin_unreachable(struct unreachable_data *data)
398 {
399 	ubsan_prologue(&data->location);
400 	pr_err("calling __builtin_unreachable()\n");
401 	ubsan_epilogue();
402 	panic("can't return from __builtin_unreachable()");
403 }
404 EXPORT_SYMBOL(__ubsan_handle_builtin_unreachable);
405 
406 void __ubsan_handle_load_invalid_value(struct invalid_value_data *data,
407 				void *val)
408 {
409 	char val_str[VALUE_LENGTH];
410 
411 	if (suppress_report(&data->location))
412 		return;
413 
414 	ubsan_prologue(&data->location);
415 
416 	val_to_string(val_str, sizeof(val_str), data->type, val);
417 
418 	pr_err("load of value %s is not a valid value for type %s\n",
419 		val_str, data->type->type_name);
420 
421 	ubsan_epilogue();
422 }
423 EXPORT_SYMBOL(__ubsan_handle_load_invalid_value);
424