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a28a6e86 FL |
1 | /* SPDX-License-Identifier: GPL-2.0 */ |
2 | #ifndef _LINUX_FORTIFY_STRING_H_ | |
3 | #define _LINUX_FORTIFY_STRING_H_ | |
4 | ||
54d9469b | 5 | #include <linux/bug.h> |
67ebc3ab | 6 | #include <linux/const.h> |
311fb40a | 7 | #include <linux/limits.h> |
67ebc3ab | 8 | |
281d0c96 | 9 | #define __FORTIFY_INLINE extern __always_inline __gnu_inline __overloadable |
c430f600 KC |
10 | #define __RENAME(x) __asm__(#x) |
11 | ||
12 | void fortify_panic(const char *name) __noreturn __cold; | |
13 | void __read_overflow(void) __compiletime_error("detected read beyond size of object (1st parameter)"); | |
14 | void __read_overflow2(void) __compiletime_error("detected read beyond size of object (2nd parameter)"); | |
f68f2ff9 | 15 | void __read_overflow2_field(size_t avail, size_t wanted) __compiletime_warning("detected read beyond size of field (2nd parameter); maybe use struct_group()?"); |
c430f600 | 16 | void __write_overflow(void) __compiletime_error("detected write beyond size of object (1st parameter)"); |
f68f2ff9 | 17 | void __write_overflow_field(size_t avail, size_t wanted) __compiletime_warning("detected write beyond size of field (1st parameter); maybe use struct_group()?"); |
a28a6e86 | 18 | |
95cadae3 QC |
19 | #define __compiletime_strlen(p) \ |
20 | ({ \ | |
e9a40e15 | 21 | char *__p = (char *)(p); \ |
311fb40a | 22 | size_t __ret = SIZE_MAX; \ |
9f7d69c5 | 23 | size_t __p_size = __member_size(p); \ |
311fb40a | 24 | if (__p_size != SIZE_MAX && \ |
d07c0acb | 25 | __builtin_constant_p(*__p)) { \ |
95cadae3 QC |
26 | size_t __p_len = __p_size - 1; \ |
27 | if (__builtin_constant_p(__p[__p_len]) && \ | |
28 | __p[__p_len] == '\0') \ | |
29 | __ret = __builtin_strlen(__p); \ | |
30 | } \ | |
31 | __ret; \ | |
3009f891 KC |
32 | }) |
33 | ||
a28a6e86 FL |
34 | #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS) |
35 | extern void *__underlying_memchr(const void *p, int c, __kernel_size_t size) __RENAME(memchr); | |
36 | extern int __underlying_memcmp(const void *p, const void *q, __kernel_size_t size) __RENAME(memcmp); | |
37 | extern void *__underlying_memcpy(void *p, const void *q, __kernel_size_t size) __RENAME(memcpy); | |
38 | extern void *__underlying_memmove(void *p, const void *q, __kernel_size_t size) __RENAME(memmove); | |
39 | extern void *__underlying_memset(void *p, int c, __kernel_size_t size) __RENAME(memset); | |
40 | extern char *__underlying_strcat(char *p, const char *q) __RENAME(strcat); | |
41 | extern char *__underlying_strcpy(char *p, const char *q) __RENAME(strcpy); | |
42 | extern __kernel_size_t __underlying_strlen(const char *p) __RENAME(strlen); | |
43 | extern char *__underlying_strncat(char *p, const char *q, __kernel_size_t count) __RENAME(strncat); | |
44 | extern char *__underlying_strncpy(char *p, const char *q, __kernel_size_t size) __RENAME(strncpy); | |
45 | #else | |
78a498c3 AP |
46 | |
47 | #if defined(__SANITIZE_MEMORY__) | |
48 | /* | |
49 | * For KMSAN builds all memcpy/memset/memmove calls should be replaced by the | |
50 | * corresponding __msan_XXX functions. | |
51 | */ | |
52 | #include <linux/kmsan_string.h> | |
53 | #define __underlying_memcpy __msan_memcpy | |
54 | #define __underlying_memmove __msan_memmove | |
55 | #define __underlying_memset __msan_memset | |
56 | #else | |
a28a6e86 FL |
57 | #define __underlying_memcpy __builtin_memcpy |
58 | #define __underlying_memmove __builtin_memmove | |
59 | #define __underlying_memset __builtin_memset | |
78a498c3 AP |
60 | #endif |
61 | ||
62 | #define __underlying_memchr __builtin_memchr | |
63 | #define __underlying_memcmp __builtin_memcmp | |
a28a6e86 FL |
64 | #define __underlying_strcat __builtin_strcat |
65 | #define __underlying_strcpy __builtin_strcpy | |
66 | #define __underlying_strlen __builtin_strlen | |
67 | #define __underlying_strncat __builtin_strncat | |
68 | #define __underlying_strncpy __builtin_strncpy | |
69 | #endif | |
70 | ||
43213dae KC |
71 | /** |
72 | * unsafe_memcpy - memcpy implementation with no FORTIFY bounds checking | |
73 | * | |
74 | * @dst: Destination memory address to write to | |
75 | * @src: Source memory address to read from | |
76 | * @bytes: How many bytes to write to @dst from @src | |
77 | * @justification: Free-form text or comment describing why the use is needed | |
78 | * | |
79 | * This should be used for corner cases where the compiler cannot do the | |
80 | * right thing, or during transitions between APIs, etc. It should be used | |
81 | * very rarely, and includes a place for justification detailing where bounds | |
82 | * checking has happened, and why existing solutions cannot be employed. | |
83 | */ | |
84 | #define unsafe_memcpy(dst, src, bytes, justification) \ | |
85 | __underlying_memcpy(dst, src, bytes) | |
86 | ||
281d0c96 | 87 | /* |
9f7d69c5 KC |
88 | * Clang's use of __builtin_*object_size() within inlines needs hinting via |
89 | * __pass_*object_size(). The preference is to only ever use type 1 (member | |
281d0c96 KC |
90 | * size, rather than struct size), but there remain some stragglers using |
91 | * type 0 that will be converted in the future. | |
92 | */ | |
439a1bca KC |
93 | #if __has_builtin(__builtin_dynamic_object_size) |
94 | #define POS __pass_dynamic_object_size(1) | |
95 | #define POS0 __pass_dynamic_object_size(0) | |
96 | #define __struct_size(p) __builtin_dynamic_object_size(p, 0) | |
97 | #define __member_size(p) __builtin_dynamic_object_size(p, 1) | |
98 | #else | |
9f7d69c5 KC |
99 | #define POS __pass_object_size(1) |
100 | #define POS0 __pass_object_size(0) | |
101 | #define __struct_size(p) __builtin_object_size(p, 0) | |
102 | #define __member_size(p) __builtin_object_size(p, 1) | |
439a1bca | 103 | #endif |
281d0c96 | 104 | |
fa35198f KC |
105 | #define __compiletime_lessthan(bounds, length) ( \ |
106 | __builtin_constant_p((bounds) < (length)) && \ | |
107 | (bounds) < (length) \ | |
108 | ) | |
109 | ||
dfbafa70 KC |
110 | /** |
111 | * strncpy - Copy a string to memory with non-guaranteed NUL padding | |
112 | * | |
113 | * @p: pointer to destination of copy | |
114 | * @q: pointer to NUL-terminated source string to copy | |
115 | * @size: bytes to write at @p | |
116 | * | |
117 | * If strlen(@q) >= @size, the copy of @q will stop after @size bytes, | |
118 | * and @p will NOT be NUL-terminated | |
119 | * | |
120 | * If strlen(@q) < @size, following the copy of @q, trailing NUL bytes | |
121 | * will be written to @p until @size total bytes have been written. | |
122 | * | |
123 | * Do not use this function. While FORTIFY_SOURCE tries to avoid | |
124 | * over-reads of @q, it cannot defend against writing unterminated | |
125 | * results to @p. Using strncpy() remains ambiguous and fragile. | |
126 | * Instead, please choose an alternative, so that the expectation | |
127 | * of @p's contents is unambiguous: | |
128 | * | |
03699f27 KC |
129 | * +--------------------+--------------------+------------+ |
130 | * | **p** needs to be: | padded to **size** | not padded | | |
131 | * +====================+====================+============+ | |
132 | * | NUL-terminated | strscpy_pad() | strscpy() | | |
133 | * +--------------------+--------------------+------------+ | |
134 | * | not NUL-terminated | strtomem_pad() | strtomem() | | |
135 | * +--------------------+--------------------+------------+ | |
dfbafa70 KC |
136 | * |
137 | * Note strscpy*()'s differing return values for detecting truncation, | |
138 | * and strtomem*()'s expectation that the destination is marked with | |
139 | * __nonstring when it is a character array. | |
140 | * | |
141 | */ | |
92df138a | 142 | __FORTIFY_INLINE __diagnose_as(__builtin_strncpy, 1, 2, 3) |
281d0c96 | 143 | char *strncpy(char * const POS p, const char *q, __kernel_size_t size) |
a28a6e86 | 144 | { |
9f7d69c5 | 145 | size_t p_size = __member_size(p); |
a28a6e86 | 146 | |
fa35198f | 147 | if (__compiletime_lessthan(p_size, size)) |
a28a6e86 FL |
148 | __write_overflow(); |
149 | if (p_size < size) | |
150 | fortify_panic(__func__); | |
151 | return __underlying_strncpy(p, q, size); | |
152 | } | |
153 | ||
03699f27 KC |
154 | /** |
155 | * strcat - Append a string to an existing string | |
156 | * | |
157 | * @p: pointer to NUL-terminated string to append to | |
158 | * @q: pointer to NUL-terminated source string to append from | |
159 | * | |
160 | * Do not use this function. While FORTIFY_SOURCE tries to avoid | |
161 | * read and write overflows, this is only possible when the | |
162 | * destination buffer size is known to the compiler. Prefer | |
163 | * building the string with formatting, via scnprintf() or similar. | |
164 | * At the very least, use strncat(). | |
165 | * | |
166 | * Returns @p. | |
167 | * | |
168 | */ | |
92df138a | 169 | __FORTIFY_INLINE __diagnose_as(__builtin_strcat, 1, 2) |
281d0c96 | 170 | char *strcat(char * const POS p, const char *q) |
a28a6e86 | 171 | { |
9f7d69c5 | 172 | size_t p_size = __member_size(p); |
a28a6e86 | 173 | |
311fb40a | 174 | if (p_size == SIZE_MAX) |
a28a6e86 FL |
175 | return __underlying_strcat(p, q); |
176 | if (strlcat(p, q, p_size) >= p_size) | |
177 | fortify_panic(__func__); | |
178 | return p; | |
179 | } | |
180 | ||
369cd216 | 181 | extern __kernel_size_t __real_strnlen(const char *, __kernel_size_t) __RENAME(strnlen); |
03699f27 KC |
182 | /** |
183 | * strnlen - Return bounded count of characters in a NUL-terminated string | |
184 | * | |
185 | * @p: pointer to NUL-terminated string to count. | |
186 | * @maxlen: maximum number of characters to count. | |
187 | * | |
188 | * Returns number of characters in @p (NOT including the final NUL), or | |
189 | * @maxlen, if no NUL has been found up to there. | |
190 | * | |
191 | */ | |
281d0c96 | 192 | __FORTIFY_INLINE __kernel_size_t strnlen(const char * const POS p, __kernel_size_t maxlen) |
369cd216 | 193 | { |
9f7d69c5 | 194 | size_t p_size = __member_size(p); |
3009f891 KC |
195 | size_t p_len = __compiletime_strlen(p); |
196 | size_t ret; | |
197 | ||
198 | /* We can take compile-time actions when maxlen is const. */ | |
311fb40a | 199 | if (__builtin_constant_p(maxlen) && p_len != SIZE_MAX) { |
3009f891 KC |
200 | /* If p is const, we can use its compile-time-known len. */ |
201 | if (maxlen >= p_size) | |
202 | return p_len; | |
203 | } | |
369cd216 | 204 | |
3009f891 KC |
205 | /* Do not check characters beyond the end of p. */ |
206 | ret = __real_strnlen(p, maxlen < p_size ? maxlen : p_size); | |
369cd216 KC |
207 | if (p_size <= ret && maxlen != ret) |
208 | fortify_panic(__func__); | |
209 | return ret; | |
210 | } | |
211 | ||
67ebc3ab KC |
212 | /* |
213 | * Defined after fortified strnlen to reuse it. However, it must still be | |
214 | * possible for strlen() to be used on compile-time strings for use in | |
215 | * static initializers (i.e. as a constant expression). | |
216 | */ | |
03699f27 KC |
217 | /** |
218 | * strlen - Return count of characters in a NUL-terminated string | |
219 | * | |
220 | * @p: pointer to NUL-terminated string to count. | |
221 | * | |
222 | * Do not use this function unless the string length is known at | |
223 | * compile-time. When @p is unterminated, this function may crash | |
224 | * or return unexpected counts that could lead to memory content | |
225 | * exposures. Prefer strnlen(). | |
226 | * | |
227 | * Returns number of characters in @p (NOT including the final NUL). | |
228 | * | |
229 | */ | |
67ebc3ab KC |
230 | #define strlen(p) \ |
231 | __builtin_choose_expr(__is_constexpr(__builtin_strlen(p)), \ | |
232 | __builtin_strlen(p), __fortify_strlen(p)) | |
92df138a | 233 | __FORTIFY_INLINE __diagnose_as(__builtin_strlen, 1) |
281d0c96 | 234 | __kernel_size_t __fortify_strlen(const char * const POS p) |
a28a6e86 FL |
235 | { |
236 | __kernel_size_t ret; | |
9f7d69c5 | 237 | size_t p_size = __member_size(p); |
a28a6e86 | 238 | |
3009f891 | 239 | /* Give up if we don't know how large p is. */ |
311fb40a | 240 | if (p_size == SIZE_MAX) |
a28a6e86 FL |
241 | return __underlying_strlen(p); |
242 | ret = strnlen(p, p_size); | |
243 | if (p_size <= ret) | |
244 | fortify_panic(__func__); | |
245 | return ret; | |
246 | } | |
247 | ||
03699f27 | 248 | /* Defined after fortified strlen() to reuse it. */ |
a28a6e86 | 249 | extern size_t __real_strlcpy(char *, const char *, size_t) __RENAME(strlcpy); |
03699f27 KC |
250 | /** |
251 | * strlcpy - Copy a string into another string buffer | |
252 | * | |
253 | * @p: pointer to destination of copy | |
254 | * @q: pointer to NUL-terminated source string to copy | |
255 | * @size: maximum number of bytes to write at @p | |
256 | * | |
257 | * If strlen(@q) >= @size, the copy of @q will be truncated at | |
258 | * @size - 1 bytes. @p will always be NUL-terminated. | |
259 | * | |
260 | * Do not use this function. While FORTIFY_SOURCE tries to avoid | |
261 | * over-reads when calculating strlen(@q), it is still possible. | |
262 | * Prefer strscpy(), though note its different return values for | |
263 | * detecting truncation. | |
264 | * | |
265 | * Returns total number of bytes written to @p, including terminating NUL. | |
266 | * | |
267 | */ | |
281d0c96 | 268 | __FORTIFY_INLINE size_t strlcpy(char * const POS p, const char * const POS q, size_t size) |
a28a6e86 | 269 | { |
9f7d69c5 KC |
270 | size_t p_size = __member_size(p); |
271 | size_t q_size = __member_size(q); | |
3009f891 KC |
272 | size_t q_len; /* Full count of source string length. */ |
273 | size_t len; /* Count of characters going into destination. */ | |
a28a6e86 | 274 | |
311fb40a | 275 | if (p_size == SIZE_MAX && q_size == SIZE_MAX) |
a28a6e86 | 276 | return __real_strlcpy(p, q, size); |
3009f891 KC |
277 | q_len = strlen(q); |
278 | len = (q_len >= size) ? size - 1 : q_len; | |
279 | if (__builtin_constant_p(size) && __builtin_constant_p(q_len) && size) { | |
280 | /* Write size is always larger than destination. */ | |
281 | if (len >= p_size) | |
a28a6e86 | 282 | __write_overflow(); |
3009f891 KC |
283 | } |
284 | if (size) { | |
a28a6e86 FL |
285 | if (len >= p_size) |
286 | fortify_panic(__func__); | |
287 | __underlying_memcpy(p, q, len); | |
288 | p[len] = '\0'; | |
289 | } | |
3009f891 | 290 | return q_len; |
a28a6e86 FL |
291 | } |
292 | ||
03699f27 | 293 | /* Defined after fortified strnlen() to reuse it. */ |
a28a6e86 | 294 | extern ssize_t __real_strscpy(char *, const char *, size_t) __RENAME(strscpy); |
03699f27 KC |
295 | /** |
296 | * strscpy - Copy a C-string into a sized buffer | |
297 | * | |
298 | * @p: Where to copy the string to | |
299 | * @q: Where to copy the string from | |
300 | * @size: Size of destination buffer | |
301 | * | |
302 | * Copy the source string @p, or as much of it as fits, into the destination | |
303 | * @q buffer. The behavior is undefined if the string buffers overlap. The | |
304 | * destination @p buffer is always NUL terminated, unless it's zero-sized. | |
305 | * | |
306 | * Preferred to strlcpy() since the API doesn't require reading memory | |
307 | * from the source @q string beyond the specified @size bytes, and since | |
308 | * the return value is easier to error-check than strlcpy()'s. | |
309 | * In addition, the implementation is robust to the string changing out | |
310 | * from underneath it, unlike the current strlcpy() implementation. | |
311 | * | |
312 | * Preferred to strncpy() since it always returns a valid string, and | |
313 | * doesn't unnecessarily force the tail of the destination buffer to be | |
314 | * zero padded. If padding is desired please use strscpy_pad(). | |
315 | * | |
316 | * Returns the number of characters copied in @p (not including the | |
317 | * trailing %NUL) or -E2BIG if @size is 0 or the copy of @q was truncated. | |
318 | */ | |
281d0c96 | 319 | __FORTIFY_INLINE ssize_t strscpy(char * const POS p, const char * const POS q, size_t size) |
a28a6e86 FL |
320 | { |
321 | size_t len; | |
322 | /* Use string size rather than possible enclosing struct size. */ | |
9f7d69c5 KC |
323 | size_t p_size = __member_size(p); |
324 | size_t q_size = __member_size(q); | |
a28a6e86 FL |
325 | |
326 | /* If we cannot get size of p and q default to call strscpy. */ | |
311fb40a | 327 | if (p_size == SIZE_MAX && q_size == SIZE_MAX) |
a28a6e86 FL |
328 | return __real_strscpy(p, q, size); |
329 | ||
330 | /* | |
331 | * If size can be known at compile time and is greater than | |
332 | * p_size, generate a compile time write overflow error. | |
333 | */ | |
fa35198f | 334 | if (__compiletime_lessthan(p_size, size)) |
a28a6e86 FL |
335 | __write_overflow(); |
336 | ||
62e1cbfc KC |
337 | /* Short-circuit for compile-time known-safe lengths. */ |
338 | if (__compiletime_lessthan(p_size, SIZE_MAX)) { | |
339 | len = __compiletime_strlen(q); | |
340 | ||
341 | if (len < SIZE_MAX && __compiletime_lessthan(len, size)) { | |
342 | __underlying_memcpy(p, q, len + 1); | |
343 | return len; | |
344 | } | |
345 | } | |
346 | ||
a28a6e86 FL |
347 | /* |
348 | * This call protects from read overflow, because len will default to q | |
349 | * length if it smaller than size. | |
350 | */ | |
351 | len = strnlen(q, size); | |
352 | /* | |
353 | * If len equals size, we will copy only size bytes which leads to | |
354 | * -E2BIG being returned. | |
355 | * Otherwise we will copy len + 1 because of the final '\O'. | |
356 | */ | |
357 | len = len == size ? size : len + 1; | |
358 | ||
359 | /* | |
360 | * Generate a runtime write overflow error if len is greater than | |
361 | * p_size. | |
362 | */ | |
363 | if (len > p_size) | |
364 | fortify_panic(__func__); | |
365 | ||
366 | /* | |
367 | * We can now safely call vanilla strscpy because we are protected from: | |
368 | * 1. Read overflow thanks to call to strnlen(). | |
369 | * 2. Write overflow thanks to above ifs. | |
370 | */ | |
371 | return __real_strscpy(p, q, len); | |
372 | } | |
373 | ||
03699f27 KC |
374 | /** |
375 | * strncat - Append a string to an existing string | |
376 | * | |
377 | * @p: pointer to NUL-terminated string to append to | |
378 | * @q: pointer to source string to append from | |
379 | * @count: Maximum bytes to read from @q | |
380 | * | |
381 | * Appends at most @count bytes from @q (stopping at the first | |
382 | * NUL byte) after the NUL-terminated string at @p. @p will be | |
383 | * NUL-terminated. | |
384 | * | |
385 | * Do not use this function. While FORTIFY_SOURCE tries to avoid | |
386 | * read and write overflows, this is only possible when the sizes | |
387 | * of @p and @q are known to the compiler. Prefer building the | |
388 | * string with formatting, via scnprintf() or similar. | |
389 | * | |
390 | * Returns @p. | |
391 | * | |
392 | */ | |
393 | /* Defined after fortified strlen() and strnlen() to reuse them. */ | |
92df138a | 394 | __FORTIFY_INLINE __diagnose_as(__builtin_strncat, 1, 2, 3) |
281d0c96 | 395 | char *strncat(char * const POS p, const char * const POS q, __kernel_size_t count) |
a28a6e86 FL |
396 | { |
397 | size_t p_len, copy_len; | |
9f7d69c5 KC |
398 | size_t p_size = __member_size(p); |
399 | size_t q_size = __member_size(q); | |
a28a6e86 | 400 | |
311fb40a | 401 | if (p_size == SIZE_MAX && q_size == SIZE_MAX) |
a28a6e86 FL |
402 | return __underlying_strncat(p, q, count); |
403 | p_len = strlen(p); | |
404 | copy_len = strnlen(q, count); | |
405 | if (p_size < p_len + copy_len + 1) | |
406 | fortify_panic(__func__); | |
407 | __underlying_memcpy(p + p_len, q, copy_len); | |
408 | p[p_len + copy_len] = '\0'; | |
409 | return p; | |
410 | } | |
411 | ||
28e77cc1 KC |
412 | __FORTIFY_INLINE void fortify_memset_chk(__kernel_size_t size, |
413 | const size_t p_size, | |
414 | const size_t p_size_field) | |
a28a6e86 | 415 | { |
28e77cc1 KC |
416 | if (__builtin_constant_p(size)) { |
417 | /* | |
418 | * Length argument is a constant expression, so we | |
419 | * can perform compile-time bounds checking where | |
fa35198f | 420 | * buffer sizes are also known at compile time. |
28e77cc1 | 421 | */ |
a28a6e86 | 422 | |
28e77cc1 | 423 | /* Error when size is larger than enclosing struct. */ |
fa35198f KC |
424 | if (__compiletime_lessthan(p_size_field, p_size) && |
425 | __compiletime_lessthan(p_size, size)) | |
28e77cc1 KC |
426 | __write_overflow(); |
427 | ||
428 | /* Warn when write size is larger than dest field. */ | |
fa35198f | 429 | if (__compiletime_lessthan(p_size_field, size)) |
28e77cc1 KC |
430 | __write_overflow_field(p_size_field, size); |
431 | } | |
432 | /* | |
433 | * At this point, length argument may not be a constant expression, | |
434 | * so run-time bounds checking can be done where buffer sizes are | |
435 | * known. (This is not an "else" because the above checks may only | |
436 | * be compile-time warnings, and we want to still warn for run-time | |
437 | * overflows.) | |
438 | */ | |
439 | ||
440 | /* | |
441 | * Always stop accesses beyond the struct that contains the | |
442 | * field, when the buffer's remaining size is known. | |
311fb40a | 443 | * (The SIZE_MAX test is to optimize away checks where the buffer |
28e77cc1 KC |
444 | * lengths are unknown.) |
445 | */ | |
311fb40a | 446 | if (p_size != SIZE_MAX && p_size < size) |
28e77cc1 | 447 | fortify_panic("memset"); |
a28a6e86 FL |
448 | } |
449 | ||
28e77cc1 KC |
450 | #define __fortify_memset_chk(p, c, size, p_size, p_size_field) ({ \ |
451 | size_t __fortify_size = (size_t)(size); \ | |
452 | fortify_memset_chk(__fortify_size, p_size, p_size_field), \ | |
453 | __underlying_memset(p, c, __fortify_size); \ | |
454 | }) | |
455 | ||
456 | /* | |
9f7d69c5 KC |
457 | * __struct_size() vs __member_size() must be captured here to avoid |
458 | * evaluating argument side-effects further into the macro layers. | |
28e77cc1 | 459 | */ |
ff901d80 | 460 | #ifndef CONFIG_KMSAN |
28e77cc1 | 461 | #define memset(p, c, s) __fortify_memset_chk(p, c, s, \ |
9f7d69c5 | 462 | __struct_size(p), __member_size(p)) |
ff901d80 | 463 | #endif |
28e77cc1 | 464 | |
f68f2ff9 KC |
465 | /* |
466 | * To make sure the compiler can enforce protection against buffer overflows, | |
467 | * memcpy(), memmove(), and memset() must not be used beyond individual | |
468 | * struct members. If you need to copy across multiple members, please use | |
469 | * struct_group() to create a named mirror of an anonymous struct union. | |
470 | * (e.g. see struct sk_buff.) Read overflow checking is currently only | |
471 | * done when a write overflow is also present, or when building with W=1. | |
472 | * | |
473 | * Mitigation coverage matrix | |
474 | * Bounds checking at: | |
475 | * +-------+-------+-------+-------+ | |
476 | * | Compile time | Run time | | |
477 | * memcpy() argument sizes: | write | read | write | read | | |
478 | * dest source length +-------+-------+-------+-------+ | |
479 | * memcpy(known, known, constant) | y | y | n/a | n/a | | |
480 | * memcpy(known, unknown, constant) | y | n | n/a | V | | |
481 | * memcpy(known, known, dynamic) | n | n | B | B | | |
482 | * memcpy(known, unknown, dynamic) | n | n | B | V | | |
483 | * memcpy(unknown, known, constant) | n | y | V | n/a | | |
484 | * memcpy(unknown, unknown, constant) | n | n | V | V | | |
485 | * memcpy(unknown, known, dynamic) | n | n | V | B | | |
486 | * memcpy(unknown, unknown, dynamic) | n | n | V | V | | |
487 | * +-------+-------+-------+-------+ | |
488 | * | |
489 | * y = perform deterministic compile-time bounds checking | |
490 | * n = cannot perform deterministic compile-time bounds checking | |
491 | * n/a = no run-time bounds checking needed since compile-time deterministic | |
492 | * B = can perform run-time bounds checking (currently unimplemented) | |
493 | * V = vulnerable to run-time overflow (will need refactoring to solve) | |
494 | * | |
495 | */ | |
54d9469b | 496 | __FORTIFY_INLINE bool fortify_memcpy_chk(__kernel_size_t size, |
f68f2ff9 KC |
497 | const size_t p_size, |
498 | const size_t q_size, | |
499 | const size_t p_size_field, | |
500 | const size_t q_size_field, | |
501 | const char *func) | |
a28a6e86 | 502 | { |
a28a6e86 | 503 | if (__builtin_constant_p(size)) { |
f68f2ff9 KC |
504 | /* |
505 | * Length argument is a constant expression, so we | |
506 | * can perform compile-time bounds checking where | |
fa35198f | 507 | * buffer sizes are also known at compile time. |
f68f2ff9 KC |
508 | */ |
509 | ||
510 | /* Error when size is larger than enclosing struct. */ | |
fa35198f KC |
511 | if (__compiletime_lessthan(p_size_field, p_size) && |
512 | __compiletime_lessthan(p_size, size)) | |
a28a6e86 | 513 | __write_overflow(); |
fa35198f KC |
514 | if (__compiletime_lessthan(q_size_field, q_size) && |
515 | __compiletime_lessthan(q_size, size)) | |
a28a6e86 | 516 | __read_overflow2(); |
f68f2ff9 KC |
517 | |
518 | /* Warn when write size argument larger than dest field. */ | |
fa35198f | 519 | if (__compiletime_lessthan(p_size_field, size)) |
f68f2ff9 KC |
520 | __write_overflow_field(p_size_field, size); |
521 | /* | |
522 | * Warn for source field over-read when building with W=1 | |
523 | * or when an over-write happened, so both can be fixed at | |
524 | * the same time. | |
525 | */ | |
fa35198f KC |
526 | if ((IS_ENABLED(KBUILD_EXTRA_WARN1) || |
527 | __compiletime_lessthan(p_size_field, size)) && | |
528 | __compiletime_lessthan(q_size_field, size)) | |
f68f2ff9 | 529 | __read_overflow2_field(q_size_field, size); |
a28a6e86 | 530 | } |
f68f2ff9 KC |
531 | /* |
532 | * At this point, length argument may not be a constant expression, | |
533 | * so run-time bounds checking can be done where buffer sizes are | |
534 | * known. (This is not an "else" because the above checks may only | |
535 | * be compile-time warnings, and we want to still warn for run-time | |
536 | * overflows.) | |
537 | */ | |
538 | ||
539 | /* | |
540 | * Always stop accesses beyond the struct that contains the | |
541 | * field, when the buffer's remaining size is known. | |
311fb40a | 542 | * (The SIZE_MAX test is to optimize away checks where the buffer |
f68f2ff9 KC |
543 | * lengths are unknown.) |
544 | */ | |
311fb40a KC |
545 | if ((p_size != SIZE_MAX && p_size < size) || |
546 | (q_size != SIZE_MAX && q_size < size)) | |
f68f2ff9 | 547 | fortify_panic(func); |
54d9469b KC |
548 | |
549 | /* | |
550 | * Warn when writing beyond destination field size. | |
551 | * | |
552 | * We must ignore p_size_field == 0 for existing 0-element | |
553 | * fake flexible arrays, until they are all converted to | |
554 | * proper flexible arrays. | |
555 | * | |
9f7d69c5 | 556 | * The implementation of __builtin_*object_size() behaves |
54d9469b KC |
557 | * like sizeof() when not directly referencing a flexible |
558 | * array member, which means there will be many bounds checks | |
559 | * that will appear at run-time, without a way for them to be | |
560 | * detected at compile-time (as can be done when the destination | |
561 | * is specifically the flexible array member). | |
562 | * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101832 | |
563 | */ | |
564 | if (p_size_field != 0 && p_size_field != SIZE_MAX && | |
565 | p_size != p_size_field && p_size_field < size) | |
566 | return true; | |
567 | ||
568 | return false; | |
a28a6e86 FL |
569 | } |
570 | ||
f68f2ff9 KC |
571 | #define __fortify_memcpy_chk(p, q, size, p_size, q_size, \ |
572 | p_size_field, q_size_field, op) ({ \ | |
6f7630b1 KC |
573 | const size_t __fortify_size = (size_t)(size); \ |
574 | const size_t __p_size = (p_size); \ | |
575 | const size_t __q_size = (q_size); \ | |
576 | const size_t __p_size_field = (p_size_field); \ | |
577 | const size_t __q_size_field = (q_size_field); \ | |
578 | WARN_ONCE(fortify_memcpy_chk(__fortify_size, __p_size, \ | |
579 | __q_size, __p_size_field, \ | |
580 | __q_size_field, #op), \ | |
54d9469b KC |
581 | #op ": detected field-spanning write (size %zu) of single %s (size %zu)\n", \ |
582 | __fortify_size, \ | |
583 | "field \"" #p "\" at " __FILE__ ":" __stringify(__LINE__), \ | |
6f7630b1 | 584 | __p_size_field); \ |
f68f2ff9 KC |
585 | __underlying_##op(p, q, __fortify_size); \ |
586 | }) | |
587 | ||
54d9469b KC |
588 | /* |
589 | * Notes about compile-time buffer size detection: | |
590 | * | |
591 | * With these types... | |
592 | * | |
593 | * struct middle { | |
594 | * u16 a; | |
595 | * u8 middle_buf[16]; | |
596 | * int b; | |
597 | * }; | |
598 | * struct end { | |
599 | * u16 a; | |
600 | * u8 end_buf[16]; | |
601 | * }; | |
602 | * struct flex { | |
603 | * int a; | |
604 | * u8 flex_buf[]; | |
605 | * }; | |
606 | * | |
607 | * void func(TYPE *ptr) { ... } | |
608 | * | |
609 | * Cases where destination size cannot be currently detected: | |
610 | * - the size of ptr's object (seemingly by design, gcc & clang fail): | |
611 | * __builtin_object_size(ptr, 1) == SIZE_MAX | |
612 | * - the size of flexible arrays in ptr's obj (by design, dynamic size): | |
613 | * __builtin_object_size(ptr->flex_buf, 1) == SIZE_MAX | |
614 | * - the size of ANY array at the end of ptr's obj (gcc and clang bug): | |
615 | * __builtin_object_size(ptr->end_buf, 1) == SIZE_MAX | |
616 | * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101836 | |
617 | * | |
618 | * Cases where destination size is currently detected: | |
619 | * - the size of non-array members within ptr's object: | |
620 | * __builtin_object_size(ptr->a, 1) == 2 | |
621 | * - the size of non-flexible-array in the middle of ptr's obj: | |
622 | * __builtin_object_size(ptr->middle_buf, 1) == 16 | |
623 | * | |
624 | */ | |
625 | ||
f68f2ff9 | 626 | /* |
9f7d69c5 KC |
627 | * __struct_size() vs __member_size() must be captured here to avoid |
628 | * evaluating argument side-effects further into the macro layers. | |
f68f2ff9 KC |
629 | */ |
630 | #define memcpy(p, q, s) __fortify_memcpy_chk(p, q, s, \ | |
9f7d69c5 KC |
631 | __struct_size(p), __struct_size(q), \ |
632 | __member_size(p), __member_size(q), \ | |
f68f2ff9 | 633 | memcpy) |
938a000e | 634 | #define memmove(p, q, s) __fortify_memcpy_chk(p, q, s, \ |
9f7d69c5 KC |
635 | __struct_size(p), __struct_size(q), \ |
636 | __member_size(p), __member_size(q), \ | |
938a000e | 637 | memmove) |
a28a6e86 FL |
638 | |
639 | extern void *__real_memscan(void *, int, __kernel_size_t) __RENAME(memscan); | |
281d0c96 | 640 | __FORTIFY_INLINE void *memscan(void * const POS0 p, int c, __kernel_size_t size) |
a28a6e86 | 641 | { |
9f7d69c5 | 642 | size_t p_size = __struct_size(p); |
a28a6e86 | 643 | |
fa35198f | 644 | if (__compiletime_lessthan(p_size, size)) |
a28a6e86 FL |
645 | __read_overflow(); |
646 | if (p_size < size) | |
647 | fortify_panic(__func__); | |
648 | return __real_memscan(p, c, size); | |
649 | } | |
650 | ||
92df138a | 651 | __FORTIFY_INLINE __diagnose_as(__builtin_memcmp, 1, 2, 3) |
281d0c96 | 652 | int memcmp(const void * const POS0 p, const void * const POS0 q, __kernel_size_t size) |
a28a6e86 | 653 | { |
9f7d69c5 KC |
654 | size_t p_size = __struct_size(p); |
655 | size_t q_size = __struct_size(q); | |
a28a6e86 FL |
656 | |
657 | if (__builtin_constant_p(size)) { | |
fa35198f | 658 | if (__compiletime_lessthan(p_size, size)) |
a28a6e86 | 659 | __read_overflow(); |
fa35198f | 660 | if (__compiletime_lessthan(q_size, size)) |
a28a6e86 FL |
661 | __read_overflow2(); |
662 | } | |
663 | if (p_size < size || q_size < size) | |
664 | fortify_panic(__func__); | |
665 | return __underlying_memcmp(p, q, size); | |
666 | } | |
667 | ||
92df138a | 668 | __FORTIFY_INLINE __diagnose_as(__builtin_memchr, 1, 2, 3) |
281d0c96 | 669 | void *memchr(const void * const POS0 p, int c, __kernel_size_t size) |
a28a6e86 | 670 | { |
9f7d69c5 | 671 | size_t p_size = __struct_size(p); |
a28a6e86 | 672 | |
fa35198f | 673 | if (__compiletime_lessthan(p_size, size)) |
a28a6e86 FL |
674 | __read_overflow(); |
675 | if (p_size < size) | |
676 | fortify_panic(__func__); | |
677 | return __underlying_memchr(p, c, size); | |
678 | } | |
679 | ||
680 | void *__real_memchr_inv(const void *s, int c, size_t n) __RENAME(memchr_inv); | |
281d0c96 | 681 | __FORTIFY_INLINE void *memchr_inv(const void * const POS0 p, int c, size_t size) |
a28a6e86 | 682 | { |
9f7d69c5 | 683 | size_t p_size = __struct_size(p); |
a28a6e86 | 684 | |
fa35198f | 685 | if (__compiletime_lessthan(p_size, size)) |
a28a6e86 FL |
686 | __read_overflow(); |
687 | if (p_size < size) | |
688 | fortify_panic(__func__); | |
689 | return __real_memchr_inv(p, c, size); | |
690 | } | |
691 | ||
9e4a6177 KC |
692 | extern void *__real_kmemdup(const void *src, size_t len, gfp_t gfp) __RENAME(kmemdup) |
693 | __realloc_size(2); | |
281d0c96 | 694 | __FORTIFY_INLINE void *kmemdup(const void * const POS0 p, size_t size, gfp_t gfp) |
a28a6e86 | 695 | { |
9f7d69c5 | 696 | size_t p_size = __struct_size(p); |
a28a6e86 | 697 | |
fa35198f | 698 | if (__compiletime_lessthan(p_size, size)) |
a28a6e86 FL |
699 | __read_overflow(); |
700 | if (p_size < size) | |
701 | fortify_panic(__func__); | |
702 | return __real_kmemdup(p, size, gfp); | |
703 | } | |
704 | ||
03699f27 KC |
705 | /** |
706 | * strcpy - Copy a string into another string buffer | |
707 | * | |
708 | * @p: pointer to destination of copy | |
709 | * @q: pointer to NUL-terminated source string to copy | |
710 | * | |
711 | * Do not use this function. While FORTIFY_SOURCE tries to avoid | |
712 | * overflows, this is only possible when the sizes of @q and @p are | |
713 | * known to the compiler. Prefer strscpy(), though note its different | |
714 | * return values for detecting truncation. | |
715 | * | |
716 | * Returns @p. | |
717 | * | |
718 | */ | |
f68f2ff9 | 719 | /* Defined after fortified strlen to reuse it. */ |
92df138a | 720 | __FORTIFY_INLINE __diagnose_as(__builtin_strcpy, 1, 2) |
281d0c96 | 721 | char *strcpy(char * const POS p, const char * const POS q) |
a28a6e86 | 722 | { |
9f7d69c5 KC |
723 | size_t p_size = __member_size(p); |
724 | size_t q_size = __member_size(q); | |
a28a6e86 FL |
725 | size_t size; |
726 | ||
f68f2ff9 | 727 | /* If neither buffer size is known, immediately give up. */ |
fa35198f KC |
728 | if (__builtin_constant_p(p_size) && |
729 | __builtin_constant_p(q_size) && | |
730 | p_size == SIZE_MAX && q_size == SIZE_MAX) | |
a28a6e86 FL |
731 | return __underlying_strcpy(p, q); |
732 | size = strlen(q) + 1; | |
072af0c6 | 733 | /* Compile-time check for const size overflow. */ |
fa35198f | 734 | if (__compiletime_lessthan(p_size, size)) |
072af0c6 KC |
735 | __write_overflow(); |
736 | /* Run-time check for dynamic size overflow. */ | |
a28a6e86 FL |
737 | if (p_size < size) |
738 | fortify_panic(__func__); | |
f68f2ff9 | 739 | __underlying_memcpy(p, q, size); |
a28a6e86 FL |
740 | return p; |
741 | } | |
742 | ||
743 | /* Don't use these outside the FORITFY_SOURCE implementation */ | |
744 | #undef __underlying_memchr | |
745 | #undef __underlying_memcmp | |
a28a6e86 FL |
746 | #undef __underlying_strcat |
747 | #undef __underlying_strcpy | |
748 | #undef __underlying_strlen | |
749 | #undef __underlying_strncat | |
750 | #undef __underlying_strncpy | |
751 | ||
281d0c96 KC |
752 | #undef POS |
753 | #undef POS0 | |
754 | ||
a28a6e86 | 755 | #endif /* _LINUX_FORTIFY_STRING_H_ */ |