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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; \ |
21a2c74b | 23 | const 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) | |
439a1bca | 96 | #else |
9f7d69c5 KC |
97 | #define POS __pass_object_size(1) |
98 | #define POS0 __pass_object_size(0) | |
439a1bca | 99 | #endif |
281d0c96 | 100 | |
fa35198f KC |
101 | #define __compiletime_lessthan(bounds, length) ( \ |
102 | __builtin_constant_p((bounds) < (length)) && \ | |
103 | (bounds) < (length) \ | |
104 | ) | |
105 | ||
dfbafa70 KC |
106 | /** |
107 | * strncpy - Copy a string to memory with non-guaranteed NUL padding | |
108 | * | |
109 | * @p: pointer to destination of copy | |
110 | * @q: pointer to NUL-terminated source string to copy | |
111 | * @size: bytes to write at @p | |
112 | * | |
113 | * If strlen(@q) >= @size, the copy of @q will stop after @size bytes, | |
114 | * and @p will NOT be NUL-terminated | |
115 | * | |
116 | * If strlen(@q) < @size, following the copy of @q, trailing NUL bytes | |
117 | * will be written to @p until @size total bytes have been written. | |
118 | * | |
119 | * Do not use this function. While FORTIFY_SOURCE tries to avoid | |
120 | * over-reads of @q, it cannot defend against writing unterminated | |
121 | * results to @p. Using strncpy() remains ambiguous and fragile. | |
122 | * Instead, please choose an alternative, so that the expectation | |
123 | * of @p's contents is unambiguous: | |
124 | * | |
03699f27 KC |
125 | * +--------------------+--------------------+------------+ |
126 | * | **p** needs to be: | padded to **size** | not padded | | |
127 | * +====================+====================+============+ | |
128 | * | NUL-terminated | strscpy_pad() | strscpy() | | |
129 | * +--------------------+--------------------+------------+ | |
130 | * | not NUL-terminated | strtomem_pad() | strtomem() | | |
131 | * +--------------------+--------------------+------------+ | |
dfbafa70 KC |
132 | * |
133 | * Note strscpy*()'s differing return values for detecting truncation, | |
134 | * and strtomem*()'s expectation that the destination is marked with | |
135 | * __nonstring when it is a character array. | |
136 | * | |
137 | */ | |
92df138a | 138 | __FORTIFY_INLINE __diagnose_as(__builtin_strncpy, 1, 2, 3) |
281d0c96 | 139 | char *strncpy(char * const POS p, const char *q, __kernel_size_t size) |
a28a6e86 | 140 | { |
21a2c74b | 141 | const size_t p_size = __member_size(p); |
a28a6e86 | 142 | |
fa35198f | 143 | if (__compiletime_lessthan(p_size, size)) |
a28a6e86 FL |
144 | __write_overflow(); |
145 | if (p_size < size) | |
146 | fortify_panic(__func__); | |
147 | return __underlying_strncpy(p, q, size); | |
148 | } | |
149 | ||
369cd216 | 150 | extern __kernel_size_t __real_strnlen(const char *, __kernel_size_t) __RENAME(strnlen); |
03699f27 KC |
151 | /** |
152 | * strnlen - Return bounded count of characters in a NUL-terminated string | |
153 | * | |
154 | * @p: pointer to NUL-terminated string to count. | |
155 | * @maxlen: maximum number of characters to count. | |
156 | * | |
157 | * Returns number of characters in @p (NOT including the final NUL), or | |
158 | * @maxlen, if no NUL has been found up to there. | |
159 | * | |
160 | */ | |
281d0c96 | 161 | __FORTIFY_INLINE __kernel_size_t strnlen(const char * const POS p, __kernel_size_t maxlen) |
369cd216 | 162 | { |
21a2c74b KC |
163 | const size_t p_size = __member_size(p); |
164 | const size_t p_len = __compiletime_strlen(p); | |
3009f891 KC |
165 | size_t ret; |
166 | ||
167 | /* We can take compile-time actions when maxlen is const. */ | |
311fb40a | 168 | if (__builtin_constant_p(maxlen) && p_len != SIZE_MAX) { |
3009f891 KC |
169 | /* If p is const, we can use its compile-time-known len. */ |
170 | if (maxlen >= p_size) | |
171 | return p_len; | |
172 | } | |
369cd216 | 173 | |
3009f891 KC |
174 | /* Do not check characters beyond the end of p. */ |
175 | ret = __real_strnlen(p, maxlen < p_size ? maxlen : p_size); | |
369cd216 KC |
176 | if (p_size <= ret && maxlen != ret) |
177 | fortify_panic(__func__); | |
178 | return ret; | |
179 | } | |
180 | ||
67ebc3ab KC |
181 | /* |
182 | * Defined after fortified strnlen to reuse it. However, it must still be | |
183 | * possible for strlen() to be used on compile-time strings for use in | |
184 | * static initializers (i.e. as a constant expression). | |
185 | */ | |
03699f27 KC |
186 | /** |
187 | * strlen - Return count of characters in a NUL-terminated string | |
188 | * | |
189 | * @p: pointer to NUL-terminated string to count. | |
190 | * | |
191 | * Do not use this function unless the string length is known at | |
192 | * compile-time. When @p is unterminated, this function may crash | |
193 | * or return unexpected counts that could lead to memory content | |
194 | * exposures. Prefer strnlen(). | |
195 | * | |
196 | * Returns number of characters in @p (NOT including the final NUL). | |
197 | * | |
198 | */ | |
67ebc3ab KC |
199 | #define strlen(p) \ |
200 | __builtin_choose_expr(__is_constexpr(__builtin_strlen(p)), \ | |
201 | __builtin_strlen(p), __fortify_strlen(p)) | |
92df138a | 202 | __FORTIFY_INLINE __diagnose_as(__builtin_strlen, 1) |
281d0c96 | 203 | __kernel_size_t __fortify_strlen(const char * const POS p) |
a28a6e86 | 204 | { |
21a2c74b | 205 | const size_t p_size = __member_size(p); |
a28a6e86 | 206 | __kernel_size_t ret; |
a28a6e86 | 207 | |
3009f891 | 208 | /* Give up if we don't know how large p is. */ |
311fb40a | 209 | if (p_size == SIZE_MAX) |
a28a6e86 FL |
210 | return __underlying_strlen(p); |
211 | ret = strnlen(p, p_size); | |
212 | if (p_size <= ret) | |
213 | fortify_panic(__func__); | |
214 | return ret; | |
215 | } | |
216 | ||
03699f27 | 217 | /* Defined after fortified strlen() to reuse it. */ |
a28a6e86 | 218 | extern size_t __real_strlcpy(char *, const char *, size_t) __RENAME(strlcpy); |
03699f27 KC |
219 | /** |
220 | * strlcpy - Copy a string into another string buffer | |
221 | * | |
222 | * @p: pointer to destination of copy | |
223 | * @q: pointer to NUL-terminated source string to copy | |
224 | * @size: maximum number of bytes to write at @p | |
225 | * | |
226 | * If strlen(@q) >= @size, the copy of @q will be truncated at | |
227 | * @size - 1 bytes. @p will always be NUL-terminated. | |
228 | * | |
229 | * Do not use this function. While FORTIFY_SOURCE tries to avoid | |
230 | * over-reads when calculating strlen(@q), it is still possible. | |
231 | * Prefer strscpy(), though note its different return values for | |
232 | * detecting truncation. | |
233 | * | |
234 | * Returns total number of bytes written to @p, including terminating NUL. | |
235 | * | |
236 | */ | |
281d0c96 | 237 | __FORTIFY_INLINE size_t strlcpy(char * const POS p, const char * const POS q, size_t size) |
a28a6e86 | 238 | { |
21a2c74b KC |
239 | const size_t p_size = __member_size(p); |
240 | const size_t q_size = __member_size(q); | |
3009f891 KC |
241 | size_t q_len; /* Full count of source string length. */ |
242 | size_t len; /* Count of characters going into destination. */ | |
a28a6e86 | 243 | |
311fb40a | 244 | if (p_size == SIZE_MAX && q_size == SIZE_MAX) |
a28a6e86 | 245 | return __real_strlcpy(p, q, size); |
3009f891 KC |
246 | q_len = strlen(q); |
247 | len = (q_len >= size) ? size - 1 : q_len; | |
248 | if (__builtin_constant_p(size) && __builtin_constant_p(q_len) && size) { | |
249 | /* Write size is always larger than destination. */ | |
250 | if (len >= p_size) | |
a28a6e86 | 251 | __write_overflow(); |
3009f891 KC |
252 | } |
253 | if (size) { | |
a28a6e86 FL |
254 | if (len >= p_size) |
255 | fortify_panic(__func__); | |
256 | __underlying_memcpy(p, q, len); | |
257 | p[len] = '\0'; | |
258 | } | |
3009f891 | 259 | return q_len; |
a28a6e86 FL |
260 | } |
261 | ||
03699f27 | 262 | /* Defined after fortified strnlen() to reuse it. */ |
a28a6e86 | 263 | extern ssize_t __real_strscpy(char *, const char *, size_t) __RENAME(strscpy); |
03699f27 KC |
264 | /** |
265 | * strscpy - Copy a C-string into a sized buffer | |
266 | * | |
267 | * @p: Where to copy the string to | |
268 | * @q: Where to copy the string from | |
269 | * @size: Size of destination buffer | |
270 | * | |
ead62aa3 AW |
271 | * Copy the source string @q, or as much of it as fits, into the destination |
272 | * @p buffer. The behavior is undefined if the string buffers overlap. The | |
03699f27 KC |
273 | * destination @p buffer is always NUL terminated, unless it's zero-sized. |
274 | * | |
275 | * Preferred to strlcpy() since the API doesn't require reading memory | |
276 | * from the source @q string beyond the specified @size bytes, and since | |
277 | * the return value is easier to error-check than strlcpy()'s. | |
278 | * In addition, the implementation is robust to the string changing out | |
279 | * from underneath it, unlike the current strlcpy() implementation. | |
280 | * | |
281 | * Preferred to strncpy() since it always returns a valid string, and | |
282 | * doesn't unnecessarily force the tail of the destination buffer to be | |
283 | * zero padded. If padding is desired please use strscpy_pad(). | |
284 | * | |
285 | * Returns the number of characters copied in @p (not including the | |
286 | * trailing %NUL) or -E2BIG if @size is 0 or the copy of @q was truncated. | |
287 | */ | |
281d0c96 | 288 | __FORTIFY_INLINE ssize_t strscpy(char * const POS p, const char * const POS q, size_t size) |
a28a6e86 | 289 | { |
a28a6e86 | 290 | /* Use string size rather than possible enclosing struct size. */ |
21a2c74b KC |
291 | const size_t p_size = __member_size(p); |
292 | const size_t q_size = __member_size(q); | |
293 | size_t len; | |
a28a6e86 FL |
294 | |
295 | /* If we cannot get size of p and q default to call strscpy. */ | |
311fb40a | 296 | if (p_size == SIZE_MAX && q_size == SIZE_MAX) |
a28a6e86 FL |
297 | return __real_strscpy(p, q, size); |
298 | ||
299 | /* | |
300 | * If size can be known at compile time and is greater than | |
301 | * p_size, generate a compile time write overflow error. | |
302 | */ | |
fa35198f | 303 | if (__compiletime_lessthan(p_size, size)) |
a28a6e86 FL |
304 | __write_overflow(); |
305 | ||
62e1cbfc KC |
306 | /* Short-circuit for compile-time known-safe lengths. */ |
307 | if (__compiletime_lessthan(p_size, SIZE_MAX)) { | |
308 | len = __compiletime_strlen(q); | |
309 | ||
310 | if (len < SIZE_MAX && __compiletime_lessthan(len, size)) { | |
311 | __underlying_memcpy(p, q, len + 1); | |
312 | return len; | |
313 | } | |
314 | } | |
315 | ||
a28a6e86 FL |
316 | /* |
317 | * This call protects from read overflow, because len will default to q | |
318 | * length if it smaller than size. | |
319 | */ | |
320 | len = strnlen(q, size); | |
321 | /* | |
322 | * If len equals size, we will copy only size bytes which leads to | |
323 | * -E2BIG being returned. | |
324 | * Otherwise we will copy len + 1 because of the final '\O'. | |
325 | */ | |
326 | len = len == size ? size : len + 1; | |
327 | ||
328 | /* | |
329 | * Generate a runtime write overflow error if len is greater than | |
330 | * p_size. | |
331 | */ | |
332 | if (len > p_size) | |
333 | fortify_panic(__func__); | |
334 | ||
335 | /* | |
336 | * We can now safely call vanilla strscpy because we are protected from: | |
337 | * 1. Read overflow thanks to call to strnlen(). | |
338 | * 2. Write overflow thanks to above ifs. | |
339 | */ | |
340 | return __real_strscpy(p, q, len); | |
341 | } | |
342 | ||
605395cd KC |
343 | /* Defined after fortified strlen() to reuse it. */ |
344 | extern size_t __real_strlcat(char *p, const char *q, size_t avail) __RENAME(strlcat); | |
345 | /** | |
346 | * strlcat - Append a string to an existing string | |
347 | * | |
348 | * @p: pointer to %NUL-terminated string to append to | |
349 | * @q: pointer to %NUL-terminated string to append from | |
350 | * @avail: Maximum bytes available in @p | |
351 | * | |
352 | * Appends %NUL-terminated string @q after the %NUL-terminated | |
353 | * string at @p, but will not write beyond @avail bytes total, | |
354 | * potentially truncating the copy from @q. @p will stay | |
355 | * %NUL-terminated only if a %NUL already existed within | |
356 | * the @avail bytes of @p. If so, the resulting number of | |
357 | * bytes copied from @q will be at most "@avail - strlen(@p) - 1". | |
358 | * | |
359 | * Do not use this function. While FORTIFY_SOURCE tries to avoid | |
360 | * read and write overflows, this is only possible when the sizes | |
361 | * of @p and @q are known to the compiler. Prefer building the | |
362 | * string with formatting, via scnprintf(), seq_buf, or similar. | |
363 | * | |
364 | * Returns total bytes that _would_ have been contained by @p | |
365 | * regardless of truncation, similar to snprintf(). If return | |
366 | * value is >= @avail, the string has been truncated. | |
367 | * | |
368 | */ | |
369 | __FORTIFY_INLINE | |
370 | size_t strlcat(char * const POS p, const char * const POS q, size_t avail) | |
371 | { | |
372 | const size_t p_size = __member_size(p); | |
373 | const size_t q_size = __member_size(q); | |
374 | size_t p_len, copy_len; | |
375 | size_t actual, wanted; | |
376 | ||
377 | /* Give up immediately if both buffer sizes are unknown. */ | |
378 | if (p_size == SIZE_MAX && q_size == SIZE_MAX) | |
379 | return __real_strlcat(p, q, avail); | |
380 | ||
381 | p_len = strnlen(p, avail); | |
382 | copy_len = strlen(q); | |
383 | wanted = actual = p_len + copy_len; | |
384 | ||
385 | /* Cannot append any more: report truncation. */ | |
386 | if (avail <= p_len) | |
387 | return wanted; | |
388 | ||
389 | /* Give up if string is already overflowed. */ | |
390 | if (p_size <= p_len) | |
391 | fortify_panic(__func__); | |
392 | ||
393 | if (actual >= avail) { | |
394 | copy_len = avail - p_len - 1; | |
395 | actual = p_len + copy_len; | |
396 | } | |
397 | ||
398 | /* Give up if copy will overflow. */ | |
399 | if (p_size <= actual) | |
400 | fortify_panic(__func__); | |
401 | __underlying_memcpy(p + p_len, q, copy_len); | |
402 | p[actual] = '\0'; | |
403 | ||
404 | return wanted; | |
405 | } | |
406 | ||
55c84a5c KC |
407 | /* Defined after fortified strlcat() to reuse it. */ |
408 | /** | |
409 | * strcat - Append a string to an existing string | |
410 | * | |
411 | * @p: pointer to NUL-terminated string to append to | |
412 | * @q: pointer to NUL-terminated source string to append from | |
413 | * | |
414 | * Do not use this function. While FORTIFY_SOURCE tries to avoid | |
415 | * read and write overflows, this is only possible when the | |
416 | * destination buffer size is known to the compiler. Prefer | |
417 | * building the string with formatting, via scnprintf() or similar. | |
418 | * At the very least, use strncat(). | |
419 | * | |
420 | * Returns @p. | |
421 | * | |
422 | */ | |
423 | __FORTIFY_INLINE __diagnose_as(__builtin_strcat, 1, 2) | |
424 | char *strcat(char * const POS p, const char *q) | |
425 | { | |
426 | const size_t p_size = __member_size(p); | |
427 | ||
428 | if (strlcat(p, q, p_size) >= p_size) | |
429 | fortify_panic(__func__); | |
430 | return p; | |
431 | } | |
432 | ||
03699f27 KC |
433 | /** |
434 | * strncat - Append a string to an existing string | |
435 | * | |
436 | * @p: pointer to NUL-terminated string to append to | |
437 | * @q: pointer to source string to append from | |
438 | * @count: Maximum bytes to read from @q | |
439 | * | |
440 | * Appends at most @count bytes from @q (stopping at the first | |
441 | * NUL byte) after the NUL-terminated string at @p. @p will be | |
442 | * NUL-terminated. | |
443 | * | |
444 | * Do not use this function. While FORTIFY_SOURCE tries to avoid | |
445 | * read and write overflows, this is only possible when the sizes | |
446 | * of @p and @q are known to the compiler. Prefer building the | |
447 | * string with formatting, via scnprintf() or similar. | |
448 | * | |
449 | * Returns @p. | |
450 | * | |
451 | */ | |
452 | /* Defined after fortified strlen() and strnlen() to reuse them. */ | |
92df138a | 453 | __FORTIFY_INLINE __diagnose_as(__builtin_strncat, 1, 2, 3) |
281d0c96 | 454 | char *strncat(char * const POS p, const char * const POS q, __kernel_size_t count) |
a28a6e86 | 455 | { |
21a2c74b KC |
456 | const size_t p_size = __member_size(p); |
457 | const size_t q_size = __member_size(q); | |
a28a6e86 | 458 | size_t p_len, copy_len; |
a28a6e86 | 459 | |
311fb40a | 460 | if (p_size == SIZE_MAX && q_size == SIZE_MAX) |
a28a6e86 FL |
461 | return __underlying_strncat(p, q, count); |
462 | p_len = strlen(p); | |
463 | copy_len = strnlen(q, count); | |
464 | if (p_size < p_len + copy_len + 1) | |
465 | fortify_panic(__func__); | |
466 | __underlying_memcpy(p + p_len, q, copy_len); | |
467 | p[p_len + copy_len] = '\0'; | |
468 | return p; | |
469 | } | |
470 | ||
28e77cc1 KC |
471 | __FORTIFY_INLINE void fortify_memset_chk(__kernel_size_t size, |
472 | const size_t p_size, | |
473 | const size_t p_size_field) | |
a28a6e86 | 474 | { |
28e77cc1 KC |
475 | if (__builtin_constant_p(size)) { |
476 | /* | |
477 | * Length argument is a constant expression, so we | |
478 | * can perform compile-time bounds checking where | |
fa35198f | 479 | * buffer sizes are also known at compile time. |
28e77cc1 | 480 | */ |
a28a6e86 | 481 | |
28e77cc1 | 482 | /* Error when size is larger than enclosing struct. */ |
fa35198f KC |
483 | if (__compiletime_lessthan(p_size_field, p_size) && |
484 | __compiletime_lessthan(p_size, size)) | |
28e77cc1 KC |
485 | __write_overflow(); |
486 | ||
487 | /* Warn when write size is larger than dest field. */ | |
fa35198f | 488 | if (__compiletime_lessthan(p_size_field, size)) |
28e77cc1 KC |
489 | __write_overflow_field(p_size_field, size); |
490 | } | |
491 | /* | |
492 | * At this point, length argument may not be a constant expression, | |
493 | * so run-time bounds checking can be done where buffer sizes are | |
494 | * known. (This is not an "else" because the above checks may only | |
495 | * be compile-time warnings, and we want to still warn for run-time | |
496 | * overflows.) | |
497 | */ | |
498 | ||
499 | /* | |
500 | * Always stop accesses beyond the struct that contains the | |
501 | * field, when the buffer's remaining size is known. | |
311fb40a | 502 | * (The SIZE_MAX test is to optimize away checks where the buffer |
28e77cc1 KC |
503 | * lengths are unknown.) |
504 | */ | |
311fb40a | 505 | if (p_size != SIZE_MAX && p_size < size) |
28e77cc1 | 506 | fortify_panic("memset"); |
a28a6e86 FL |
507 | } |
508 | ||
28e77cc1 KC |
509 | #define __fortify_memset_chk(p, c, size, p_size, p_size_field) ({ \ |
510 | size_t __fortify_size = (size_t)(size); \ | |
511 | fortify_memset_chk(__fortify_size, p_size, p_size_field), \ | |
512 | __underlying_memset(p, c, __fortify_size); \ | |
513 | }) | |
514 | ||
515 | /* | |
9f7d69c5 KC |
516 | * __struct_size() vs __member_size() must be captured here to avoid |
517 | * evaluating argument side-effects further into the macro layers. | |
28e77cc1 | 518 | */ |
ff901d80 | 519 | #ifndef CONFIG_KMSAN |
28e77cc1 | 520 | #define memset(p, c, s) __fortify_memset_chk(p, c, s, \ |
9f7d69c5 | 521 | __struct_size(p), __member_size(p)) |
ff901d80 | 522 | #endif |
28e77cc1 | 523 | |
f68f2ff9 KC |
524 | /* |
525 | * To make sure the compiler can enforce protection against buffer overflows, | |
526 | * memcpy(), memmove(), and memset() must not be used beyond individual | |
527 | * struct members. If you need to copy across multiple members, please use | |
528 | * struct_group() to create a named mirror of an anonymous struct union. | |
529 | * (e.g. see struct sk_buff.) Read overflow checking is currently only | |
530 | * done when a write overflow is also present, or when building with W=1. | |
531 | * | |
532 | * Mitigation coverage matrix | |
533 | * Bounds checking at: | |
534 | * +-------+-------+-------+-------+ | |
535 | * | Compile time | Run time | | |
536 | * memcpy() argument sizes: | write | read | write | read | | |
537 | * dest source length +-------+-------+-------+-------+ | |
538 | * memcpy(known, known, constant) | y | y | n/a | n/a | | |
539 | * memcpy(known, unknown, constant) | y | n | n/a | V | | |
540 | * memcpy(known, known, dynamic) | n | n | B | B | | |
541 | * memcpy(known, unknown, dynamic) | n | n | B | V | | |
542 | * memcpy(unknown, known, constant) | n | y | V | n/a | | |
543 | * memcpy(unknown, unknown, constant) | n | n | V | V | | |
544 | * memcpy(unknown, known, dynamic) | n | n | V | B | | |
545 | * memcpy(unknown, unknown, dynamic) | n | n | V | V | | |
546 | * +-------+-------+-------+-------+ | |
547 | * | |
548 | * y = perform deterministic compile-time bounds checking | |
549 | * n = cannot perform deterministic compile-time bounds checking | |
550 | * n/a = no run-time bounds checking needed since compile-time deterministic | |
551 | * B = can perform run-time bounds checking (currently unimplemented) | |
552 | * V = vulnerable to run-time overflow (will need refactoring to solve) | |
553 | * | |
554 | */ | |
54d9469b | 555 | __FORTIFY_INLINE bool fortify_memcpy_chk(__kernel_size_t size, |
f68f2ff9 KC |
556 | const size_t p_size, |
557 | const size_t q_size, | |
558 | const size_t p_size_field, | |
559 | const size_t q_size_field, | |
560 | const char *func) | |
a28a6e86 | 561 | { |
a28a6e86 | 562 | if (__builtin_constant_p(size)) { |
f68f2ff9 KC |
563 | /* |
564 | * Length argument is a constant expression, so we | |
565 | * can perform compile-time bounds checking where | |
fa35198f | 566 | * buffer sizes are also known at compile time. |
f68f2ff9 KC |
567 | */ |
568 | ||
569 | /* Error when size is larger than enclosing struct. */ | |
fa35198f KC |
570 | if (__compiletime_lessthan(p_size_field, p_size) && |
571 | __compiletime_lessthan(p_size, size)) | |
a28a6e86 | 572 | __write_overflow(); |
fa35198f KC |
573 | if (__compiletime_lessthan(q_size_field, q_size) && |
574 | __compiletime_lessthan(q_size, size)) | |
a28a6e86 | 575 | __read_overflow2(); |
f68f2ff9 KC |
576 | |
577 | /* Warn when write size argument larger than dest field. */ | |
fa35198f | 578 | if (__compiletime_lessthan(p_size_field, size)) |
f68f2ff9 KC |
579 | __write_overflow_field(p_size_field, size); |
580 | /* | |
581 | * Warn for source field over-read when building with W=1 | |
582 | * or when an over-write happened, so both can be fixed at | |
583 | * the same time. | |
584 | */ | |
fa35198f KC |
585 | if ((IS_ENABLED(KBUILD_EXTRA_WARN1) || |
586 | __compiletime_lessthan(p_size_field, size)) && | |
587 | __compiletime_lessthan(q_size_field, size)) | |
f68f2ff9 | 588 | __read_overflow2_field(q_size_field, size); |
a28a6e86 | 589 | } |
f68f2ff9 KC |
590 | /* |
591 | * At this point, length argument may not be a constant expression, | |
592 | * so run-time bounds checking can be done where buffer sizes are | |
593 | * known. (This is not an "else" because the above checks may only | |
594 | * be compile-time warnings, and we want to still warn for run-time | |
595 | * overflows.) | |
596 | */ | |
597 | ||
598 | /* | |
599 | * Always stop accesses beyond the struct that contains the | |
600 | * field, when the buffer's remaining size is known. | |
311fb40a | 601 | * (The SIZE_MAX test is to optimize away checks where the buffer |
f68f2ff9 KC |
602 | * lengths are unknown.) |
603 | */ | |
311fb40a KC |
604 | if ((p_size != SIZE_MAX && p_size < size) || |
605 | (q_size != SIZE_MAX && q_size < size)) | |
f68f2ff9 | 606 | fortify_panic(func); |
54d9469b KC |
607 | |
608 | /* | |
609 | * Warn when writing beyond destination field size. | |
610 | * | |
611 | * We must ignore p_size_field == 0 for existing 0-element | |
612 | * fake flexible arrays, until they are all converted to | |
613 | * proper flexible arrays. | |
614 | * | |
9f7d69c5 | 615 | * The implementation of __builtin_*object_size() behaves |
54d9469b KC |
616 | * like sizeof() when not directly referencing a flexible |
617 | * array member, which means there will be many bounds checks | |
618 | * that will appear at run-time, without a way for them to be | |
619 | * detected at compile-time (as can be done when the destination | |
620 | * is specifically the flexible array member). | |
621 | * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101832 | |
622 | */ | |
623 | if (p_size_field != 0 && p_size_field != SIZE_MAX && | |
624 | p_size != p_size_field && p_size_field < size) | |
625 | return true; | |
626 | ||
627 | return false; | |
a28a6e86 FL |
628 | } |
629 | ||
f68f2ff9 KC |
630 | #define __fortify_memcpy_chk(p, q, size, p_size, q_size, \ |
631 | p_size_field, q_size_field, op) ({ \ | |
6f7630b1 KC |
632 | const size_t __fortify_size = (size_t)(size); \ |
633 | const size_t __p_size = (p_size); \ | |
634 | const size_t __q_size = (q_size); \ | |
635 | const size_t __p_size_field = (p_size_field); \ | |
636 | const size_t __q_size_field = (q_size_field); \ | |
637 | WARN_ONCE(fortify_memcpy_chk(__fortify_size, __p_size, \ | |
638 | __q_size, __p_size_field, \ | |
639 | __q_size_field, #op), \ | |
54d9469b KC |
640 | #op ": detected field-spanning write (size %zu) of single %s (size %zu)\n", \ |
641 | __fortify_size, \ | |
5097a69d | 642 | "field \"" #p "\" at " FILE_LINE, \ |
6f7630b1 | 643 | __p_size_field); \ |
f68f2ff9 KC |
644 | __underlying_##op(p, q, __fortify_size); \ |
645 | }) | |
646 | ||
54d9469b KC |
647 | /* |
648 | * Notes about compile-time buffer size detection: | |
649 | * | |
650 | * With these types... | |
651 | * | |
652 | * struct middle { | |
653 | * u16 a; | |
654 | * u8 middle_buf[16]; | |
655 | * int b; | |
656 | * }; | |
657 | * struct end { | |
658 | * u16 a; | |
659 | * u8 end_buf[16]; | |
660 | * }; | |
661 | * struct flex { | |
662 | * int a; | |
663 | * u8 flex_buf[]; | |
664 | * }; | |
665 | * | |
666 | * void func(TYPE *ptr) { ... } | |
667 | * | |
668 | * Cases where destination size cannot be currently detected: | |
669 | * - the size of ptr's object (seemingly by design, gcc & clang fail): | |
670 | * __builtin_object_size(ptr, 1) == SIZE_MAX | |
671 | * - the size of flexible arrays in ptr's obj (by design, dynamic size): | |
672 | * __builtin_object_size(ptr->flex_buf, 1) == SIZE_MAX | |
673 | * - the size of ANY array at the end of ptr's obj (gcc and clang bug): | |
674 | * __builtin_object_size(ptr->end_buf, 1) == SIZE_MAX | |
675 | * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101836 | |
676 | * | |
677 | * Cases where destination size is currently detected: | |
678 | * - the size of non-array members within ptr's object: | |
679 | * __builtin_object_size(ptr->a, 1) == 2 | |
680 | * - the size of non-flexible-array in the middle of ptr's obj: | |
681 | * __builtin_object_size(ptr->middle_buf, 1) == 16 | |
682 | * | |
683 | */ | |
684 | ||
f68f2ff9 | 685 | /* |
9f7d69c5 KC |
686 | * __struct_size() vs __member_size() must be captured here to avoid |
687 | * evaluating argument side-effects further into the macro layers. | |
f68f2ff9 KC |
688 | */ |
689 | #define memcpy(p, q, s) __fortify_memcpy_chk(p, q, s, \ | |
9f7d69c5 KC |
690 | __struct_size(p), __struct_size(q), \ |
691 | __member_size(p), __member_size(q), \ | |
f68f2ff9 | 692 | memcpy) |
938a000e | 693 | #define memmove(p, q, s) __fortify_memcpy_chk(p, q, s, \ |
9f7d69c5 KC |
694 | __struct_size(p), __struct_size(q), \ |
695 | __member_size(p), __member_size(q), \ | |
938a000e | 696 | memmove) |
a28a6e86 FL |
697 | |
698 | extern void *__real_memscan(void *, int, __kernel_size_t) __RENAME(memscan); | |
281d0c96 | 699 | __FORTIFY_INLINE void *memscan(void * const POS0 p, int c, __kernel_size_t size) |
a28a6e86 | 700 | { |
21a2c74b | 701 | const size_t p_size = __struct_size(p); |
a28a6e86 | 702 | |
fa35198f | 703 | if (__compiletime_lessthan(p_size, size)) |
a28a6e86 FL |
704 | __read_overflow(); |
705 | if (p_size < size) | |
706 | fortify_panic(__func__); | |
707 | return __real_memscan(p, c, size); | |
708 | } | |
709 | ||
92df138a | 710 | __FORTIFY_INLINE __diagnose_as(__builtin_memcmp, 1, 2, 3) |
281d0c96 | 711 | int memcmp(const void * const POS0 p, const void * const POS0 q, __kernel_size_t size) |
a28a6e86 | 712 | { |
21a2c74b KC |
713 | const size_t p_size = __struct_size(p); |
714 | const size_t q_size = __struct_size(q); | |
a28a6e86 FL |
715 | |
716 | if (__builtin_constant_p(size)) { | |
fa35198f | 717 | if (__compiletime_lessthan(p_size, size)) |
a28a6e86 | 718 | __read_overflow(); |
fa35198f | 719 | if (__compiletime_lessthan(q_size, size)) |
a28a6e86 FL |
720 | __read_overflow2(); |
721 | } | |
722 | if (p_size < size || q_size < size) | |
723 | fortify_panic(__func__); | |
724 | return __underlying_memcmp(p, q, size); | |
725 | } | |
726 | ||
92df138a | 727 | __FORTIFY_INLINE __diagnose_as(__builtin_memchr, 1, 2, 3) |
281d0c96 | 728 | void *memchr(const void * const POS0 p, int c, __kernel_size_t size) |
a28a6e86 | 729 | { |
21a2c74b | 730 | const size_t p_size = __struct_size(p); |
a28a6e86 | 731 | |
fa35198f | 732 | if (__compiletime_lessthan(p_size, size)) |
a28a6e86 FL |
733 | __read_overflow(); |
734 | if (p_size < size) | |
735 | fortify_panic(__func__); | |
736 | return __underlying_memchr(p, c, size); | |
737 | } | |
738 | ||
739 | void *__real_memchr_inv(const void *s, int c, size_t n) __RENAME(memchr_inv); | |
281d0c96 | 740 | __FORTIFY_INLINE void *memchr_inv(const void * const POS0 p, int c, size_t size) |
a28a6e86 | 741 | { |
21a2c74b | 742 | const size_t p_size = __struct_size(p); |
a28a6e86 | 743 | |
fa35198f | 744 | if (__compiletime_lessthan(p_size, size)) |
a28a6e86 FL |
745 | __read_overflow(); |
746 | if (p_size < size) | |
747 | fortify_panic(__func__); | |
748 | return __real_memchr_inv(p, c, size); | |
749 | } | |
750 | ||
9e4a6177 KC |
751 | extern void *__real_kmemdup(const void *src, size_t len, gfp_t gfp) __RENAME(kmemdup) |
752 | __realloc_size(2); | |
281d0c96 | 753 | __FORTIFY_INLINE void *kmemdup(const void * const POS0 p, size_t size, gfp_t gfp) |
a28a6e86 | 754 | { |
21a2c74b | 755 | const size_t p_size = __struct_size(p); |
a28a6e86 | 756 | |
fa35198f | 757 | if (__compiletime_lessthan(p_size, size)) |
a28a6e86 FL |
758 | __read_overflow(); |
759 | if (p_size < size) | |
760 | fortify_panic(__func__); | |
761 | return __real_kmemdup(p, size, gfp); | |
762 | } | |
763 | ||
03699f27 KC |
764 | /** |
765 | * strcpy - Copy a string into another string buffer | |
766 | * | |
767 | * @p: pointer to destination of copy | |
768 | * @q: pointer to NUL-terminated source string to copy | |
769 | * | |
770 | * Do not use this function. While FORTIFY_SOURCE tries to avoid | |
771 | * overflows, this is only possible when the sizes of @q and @p are | |
772 | * known to the compiler. Prefer strscpy(), though note its different | |
773 | * return values for detecting truncation. | |
774 | * | |
775 | * Returns @p. | |
776 | * | |
777 | */ | |
f68f2ff9 | 778 | /* Defined after fortified strlen to reuse it. */ |
92df138a | 779 | __FORTIFY_INLINE __diagnose_as(__builtin_strcpy, 1, 2) |
281d0c96 | 780 | char *strcpy(char * const POS p, const char * const POS q) |
a28a6e86 | 781 | { |
21a2c74b KC |
782 | const size_t p_size = __member_size(p); |
783 | const size_t q_size = __member_size(q); | |
a28a6e86 FL |
784 | size_t size; |
785 | ||
f68f2ff9 | 786 | /* If neither buffer size is known, immediately give up. */ |
fa35198f KC |
787 | if (__builtin_constant_p(p_size) && |
788 | __builtin_constant_p(q_size) && | |
789 | p_size == SIZE_MAX && q_size == SIZE_MAX) | |
a28a6e86 FL |
790 | return __underlying_strcpy(p, q); |
791 | size = strlen(q) + 1; | |
072af0c6 | 792 | /* Compile-time check for const size overflow. */ |
fa35198f | 793 | if (__compiletime_lessthan(p_size, size)) |
072af0c6 KC |
794 | __write_overflow(); |
795 | /* Run-time check for dynamic size overflow. */ | |
a28a6e86 FL |
796 | if (p_size < size) |
797 | fortify_panic(__func__); | |
f68f2ff9 | 798 | __underlying_memcpy(p, q, size); |
a28a6e86 FL |
799 | return p; |
800 | } | |
801 | ||
802 | /* Don't use these outside the FORITFY_SOURCE implementation */ | |
803 | #undef __underlying_memchr | |
804 | #undef __underlying_memcmp | |
a28a6e86 FL |
805 | #undef __underlying_strcat |
806 | #undef __underlying_strcpy | |
807 | #undef __underlying_strlen | |
808 | #undef __underlying_strncat | |
809 | #undef __underlying_strncpy | |
810 | ||
281d0c96 KC |
811 | #undef POS |
812 | #undef POS0 | |
813 | ||
a28a6e86 | 814 | #endif /* _LINUX_FORTIFY_STRING_H_ */ |