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Linux/lib/ubsan.c

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  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 bool suppress_report(struct source_location *loc)
 49 {
 50         return current->in_ubsan || was_reported(loc);
 51 }
 52 
 53 static bool type_is_int(struct type_descriptor *type)
 54 {
 55         return type->type_kind == type_kind_int;
 56 }
 57 
 58 static bool type_is_signed(struct type_descriptor *type)
 59 {
 60         WARN_ON(!type_is_int(type));
 61         return  type->type_info & 1;
 62 }
 63 
 64 static unsigned type_bit_width(struct type_descriptor *type)
 65 {
 66         return 1 << (type->type_info >> 1);
 67 }
 68 
 69 static bool is_inline_int(struct type_descriptor *type)
 70 {
 71         unsigned inline_bits = sizeof(unsigned long)*8;
 72         unsigned bits = type_bit_width(type);
 73 
 74         WARN_ON(!type_is_int(type));
 75 
 76         return bits <= inline_bits;
 77 }
 78 
 79 static s_max get_signed_val(struct type_descriptor *type, void *val)
 80 {
 81         if (is_inline_int(type)) {
 82                 unsigned extra_bits = sizeof(s_max)*8 - type_bit_width(type);
 83                 unsigned long ulong_val = (unsigned long)val;
 84 
 85                 return ((s_max)ulong_val) << extra_bits >> extra_bits;
 86         }
 87 
 88         if (type_bit_width(type) == 64)
 89                 return *(s64 *)val;
 90 
 91         return *(s_max *)val;
 92 }
 93 
 94 static bool val_is_negative(struct type_descriptor *type, void *val)
 95 {
 96         return type_is_signed(type) && get_signed_val(type, val) < 0;
 97 }
 98 
 99 static u_max get_unsigned_val(struct type_descriptor *type, void *val)
100 {
101         if (is_inline_int(type))
102                 return (unsigned long)val;
103 
104         if (type_bit_width(type) == 64)
105                 return *(u64 *)val;
106 
107         return *(u_max *)val;
108 }
109 
110 static void val_to_string(char *str, size_t size, struct type_descriptor *type,
111                         void *value)
112 {
113         if (type_is_int(type)) {
114                 if (type_bit_width(type) == 128) {
115 #if defined(CONFIG_ARCH_SUPPORTS_INT128)
116                         u_max val = get_unsigned_val(type, value);
117 
118                         scnprintf(str, size, "0x%08x%08x%08x%08x",
119                                 (u32)(val >> 96),
120                                 (u32)(val >> 64),
121                                 (u32)(val >> 32),
122                                 (u32)(val));
123 #else
124                         WARN_ON(1);
125 #endif
126                 } else if (type_is_signed(type)) {
127                         scnprintf(str, size, "%lld",
128                                 (s64)get_signed_val(type, value));
129                 } else {
130                         scnprintf(str, size, "%llu",
131                                 (u64)get_unsigned_val(type, value));
132                 }
133         }
134 }
135 
136 static void ubsan_prologue(struct source_location *loc, const char *reason)
137 {
138         current->in_ubsan++;
139 
140         pr_err("========================================"
141                 "========================================\n");
142         pr_err("UBSAN: %s in %s:%d:%d\n", reason, loc->file_name,
143                 loc->line & LINE_MASK, loc->column & COLUMN_MASK);
144 }
145 
146 static void ubsan_epilogue(void)
147 {
148         dump_stack();
149         pr_err("========================================"
150                 "========================================\n");
151 
152         current->in_ubsan--;
153 
154         if (panic_on_warn) {
155                 /*
156                  * This thread may hit another WARN() in the panic path.
157                  * Resetting this prevents additional WARN() from panicking the
158                  * system on this thread.  Other threads are blocked by the
159                  * panic_mutex in panic().
160                  */
161                 panic_on_warn = 0;
162                 panic("panic_on_warn set ...\n");
163         }
164 }
165 
166 static void handle_overflow(struct overflow_data *data, void *lhs,
167                         void *rhs, char op)
168 {
169 
170         struct type_descriptor *type = data->type;
171         char lhs_val_str[VALUE_LENGTH];
172         char rhs_val_str[VALUE_LENGTH];
173 
174         if (suppress_report(&data->location))
175                 return;
176 
177         ubsan_prologue(&data->location, type_is_signed(type) ?
178                         "signed-integer-overflow" :
179                         "unsigned-integer-overflow");
180 
181         val_to_string(lhs_val_str, sizeof(lhs_val_str), type, lhs);
182         val_to_string(rhs_val_str, sizeof(rhs_val_str), type, rhs);
183         pr_err("%s %c %s cannot be represented in type %s\n",
184                 lhs_val_str,
185                 op,
186                 rhs_val_str,
187                 type->type_name);
188 
189         ubsan_epilogue();
190 }
191 
192 void __ubsan_handle_add_overflow(void *data,
193                                 void *lhs, void *rhs)
194 {
195 
196         handle_overflow(data, lhs, rhs, '+');
197 }
198 EXPORT_SYMBOL(__ubsan_handle_add_overflow);
199 
200 void __ubsan_handle_sub_overflow(void *data,
201                                 void *lhs, void *rhs)
202 {
203         handle_overflow(data, lhs, rhs, '-');
204 }
205 EXPORT_SYMBOL(__ubsan_handle_sub_overflow);
206 
207 void __ubsan_handle_mul_overflow(void *data,
208                                 void *lhs, void *rhs)
209 {
210         handle_overflow(data, lhs, rhs, '*');
211 }
212 EXPORT_SYMBOL(__ubsan_handle_mul_overflow);
213 
214 void __ubsan_handle_negate_overflow(void *_data, void *old_val)
215 {
216         struct overflow_data *data = _data;
217         char old_val_str[VALUE_LENGTH];
218 
219         if (suppress_report(&data->location))
220                 return;
221 
222         ubsan_prologue(&data->location, "negation-overflow");
223 
224         val_to_string(old_val_str, sizeof(old_val_str), data->type, old_val);
225 
226         pr_err("negation of %s cannot be represented in type %s:\n",
227                 old_val_str, data->type->type_name);
228 
229         ubsan_epilogue();
230 }
231 EXPORT_SYMBOL(__ubsan_handle_negate_overflow);
232 
233 
234 void __ubsan_handle_divrem_overflow(void *_data, void *lhs, void *rhs)
235 {
236         struct overflow_data *data = _data;
237         char rhs_val_str[VALUE_LENGTH];
238 
239         if (suppress_report(&data->location))
240                 return;
241 
242         ubsan_prologue(&data->location, "division-overflow");
243 
244         val_to_string(rhs_val_str, sizeof(rhs_val_str), data->type, rhs);
245 
246         if (type_is_signed(data->type) && get_signed_val(data->type, rhs) == -1)
247                 pr_err("division of %s by -1 cannot be represented in type %s\n",
248                         rhs_val_str, data->type->type_name);
249         else
250                 pr_err("division by zero\n");
251 
252         ubsan_epilogue();
253 }
254 EXPORT_SYMBOL(__ubsan_handle_divrem_overflow);
255 
256 static void handle_null_ptr_deref(struct type_mismatch_data_common *data)
257 {
258         if (suppress_report(data->location))
259                 return;
260 
261         ubsan_prologue(data->location, "null-ptr-deref");
262 
263         pr_err("%s null pointer of type %s\n",
264                 type_check_kinds[data->type_check_kind],
265                 data->type->type_name);
266 
267         ubsan_epilogue();
268 }
269 
270 static void handle_misaligned_access(struct type_mismatch_data_common *data,
271                                 unsigned long ptr)
272 {
273         if (suppress_report(data->location))
274                 return;
275 
276         ubsan_prologue(data->location, "misaligned-access");
277 
278         pr_err("%s misaligned address %p for type %s\n",
279                 type_check_kinds[data->type_check_kind],
280                 (void *)ptr, data->type->type_name);
281         pr_err("which requires %ld byte alignment\n", data->alignment);
282 
283         ubsan_epilogue();
284 }
285 
286 static void handle_object_size_mismatch(struct type_mismatch_data_common *data,
287                                         unsigned long ptr)
288 {
289         if (suppress_report(data->location))
290                 return;
291 
292         ubsan_prologue(data->location, "object-size-mismatch");
293         pr_err("%s address %p with insufficient space\n",
294                 type_check_kinds[data->type_check_kind],
295                 (void *) ptr);
296         pr_err("for an object of type %s\n", data->type->type_name);
297         ubsan_epilogue();
298 }
299 
300 static void ubsan_type_mismatch_common(struct type_mismatch_data_common *data,
301                                 unsigned long ptr)
302 {
303         unsigned long flags = user_access_save();
304 
305         if (!ptr)
306                 handle_null_ptr_deref(data);
307         else if (data->alignment && !IS_ALIGNED(ptr, data->alignment))
308                 handle_misaligned_access(data, ptr);
309         else
310                 handle_object_size_mismatch(data, ptr);
311 
312         user_access_restore(flags);
313 }
314 
315 void __ubsan_handle_type_mismatch(struct type_mismatch_data *data,
316                                 void *ptr)
317 {
318         struct type_mismatch_data_common common_data = {
319                 .location = &data->location,
320                 .type = data->type,
321                 .alignment = data->alignment,
322                 .type_check_kind = data->type_check_kind
323         };
324 
325         ubsan_type_mismatch_common(&common_data, (unsigned long)ptr);
326 }
327 EXPORT_SYMBOL(__ubsan_handle_type_mismatch);
328 
329 void __ubsan_handle_type_mismatch_v1(void *_data, void *ptr)
330 {
331         struct type_mismatch_data_v1 *data = _data;
332         struct type_mismatch_data_common common_data = {
333                 .location = &data->location,
334                 .type = data->type,
335                 .alignment = 1UL << data->log_alignment,
336                 .type_check_kind = data->type_check_kind
337         };
338 
339         ubsan_type_mismatch_common(&common_data, (unsigned long)ptr);
340 }
341 EXPORT_SYMBOL(__ubsan_handle_type_mismatch_v1);
342 
343 void __ubsan_handle_out_of_bounds(void *_data, void *index)
344 {
345         struct out_of_bounds_data *data = _data;
346         char index_str[VALUE_LENGTH];
347 
348         if (suppress_report(&data->location))
349                 return;
350 
351         ubsan_prologue(&data->location, "array-index-out-of-bounds");
352 
353         val_to_string(index_str, sizeof(index_str), data->index_type, index);
354         pr_err("index %s is out of range for type %s\n", index_str,
355                 data->array_type->type_name);
356         ubsan_epilogue();
357 }
358 EXPORT_SYMBOL(__ubsan_handle_out_of_bounds);
359 
360 void __ubsan_handle_shift_out_of_bounds(void *_data, void *lhs, void *rhs)
361 {
362         struct shift_out_of_bounds_data *data = _data;
363         struct type_descriptor *rhs_type = data->rhs_type;
364         struct type_descriptor *lhs_type = data->lhs_type;
365         char rhs_str[VALUE_LENGTH];
366         char lhs_str[VALUE_LENGTH];
367         unsigned long ua_flags = user_access_save();
368 
369         if (suppress_report(&data->location))
370                 goto out;
371 
372         ubsan_prologue(&data->location, "shift-out-of-bounds");
373 
374         val_to_string(rhs_str, sizeof(rhs_str), rhs_type, rhs);
375         val_to_string(lhs_str, sizeof(lhs_str), lhs_type, lhs);
376 
377         if (val_is_negative(rhs_type, rhs))
378                 pr_err("shift exponent %s is negative\n", rhs_str);
379 
380         else if (get_unsigned_val(rhs_type, rhs) >=
381                 type_bit_width(lhs_type))
382                 pr_err("shift exponent %s is too large for %u-bit type %s\n",
383                         rhs_str,
384                         type_bit_width(lhs_type),
385                         lhs_type->type_name);
386         else if (val_is_negative(lhs_type, lhs))
387                 pr_err("left shift of negative value %s\n",
388                         lhs_str);
389         else
390                 pr_err("left shift of %s by %s places cannot be"
391                         " represented in type %s\n",
392                         lhs_str, rhs_str,
393                         lhs_type->type_name);
394 
395         ubsan_epilogue();
396 out:
397         user_access_restore(ua_flags);
398 }
399 EXPORT_SYMBOL(__ubsan_handle_shift_out_of_bounds);
400 
401 
402 void __ubsan_handle_builtin_unreachable(void *_data)
403 {
404         struct unreachable_data *data = _data;
405         ubsan_prologue(&data->location, "unreachable");
406         pr_err("calling __builtin_unreachable()\n");
407         ubsan_epilogue();
408         panic("can't return from __builtin_unreachable()");
409 }
410 EXPORT_SYMBOL(__ubsan_handle_builtin_unreachable);
411 
412 void __ubsan_handle_load_invalid_value(void *_data, void *val)
413 {
414         struct invalid_value_data *data = _data;
415         char val_str[VALUE_LENGTH];
416 
417         if (suppress_report(&data->location))
418                 return;
419 
420         ubsan_prologue(&data->location, "invalid-load");
421 
422         val_to_string(val_str, sizeof(val_str), data->type, val);
423 
424         pr_err("load of value %s is not a valid value for type %s\n",
425                 val_str, data->type->type_name);
426 
427         ubsan_epilogue();
428 }
429 EXPORT_SYMBOL(__ubsan_handle_load_invalid_value);
430 

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