1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _LINUX_FORTIFY_STRING_H_
3#define _LINUX_FORTIFY_STRING_H_
4
5#include <linux/bug.h>
6#include <linux/const.h>
7#include <linux/limits.h>
8
9#define __FORTIFY_INLINE extern __always_inline __gnu_inline __overloadable
10#define __RENAME(x) __asm__(#x)
11
12void fortify_panic(const char *name) __noreturn __cold;
13void __read_overflow(void) __compiletime_error("detected read beyond size of object (1st parameter)");
14void __read_overflow2(void) __compiletime_error("detected read beyond size of object (2nd parameter)");
15void __read_overflow2_field(size_t avail, size_t wanted) __compiletime_warning("detected read beyond size of field (2nd parameter); maybe use struct_group()?");
16void __write_overflow(void) __compiletime_error("detected write beyond size of object (1st parameter)");
17void __write_overflow_field(size_t avail, size_t wanted) __compiletime_warning("detected write beyond size of field (1st parameter); maybe use struct_group()?");
18
19#define __compiletime_strlen(p) \
20({ \
21 char *__p = (char *)(p); \
22 size_t __ret = SIZE_MAX; \
23 const size_t __p_size = __member_size(p); \
24 if (__p_size != SIZE_MAX && \
25 __builtin_constant_p(*__p)) { \
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; \
32})
33
34#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
35extern void *__underlying_memchr(const void *p, int c, __kernel_size_t size) __RENAME(memchr);
36extern int __underlying_memcmp(const void *p, const void *q, __kernel_size_t size) __RENAME(memcmp);
37extern void *__underlying_memcpy(void *p, const void *q, __kernel_size_t size) __RENAME(memcpy);
38extern void *__underlying_memmove(void *p, const void *q, __kernel_size_t size) __RENAME(memmove);
39extern void *__underlying_memset(void *p, int c, __kernel_size_t size) __RENAME(memset);
40extern char *__underlying_strcat(char *p, const char *q) __RENAME(strcat);
41extern char *__underlying_strcpy(char *p, const char *q) __RENAME(strcpy);
42extern __kernel_size_t __underlying_strlen(const char *p) __RENAME(strlen);
43extern char *__underlying_strncat(char *p, const char *q, __kernel_size_t count) __RENAME(strncat);
44extern char *__underlying_strncpy(char *p, const char *q, __kernel_size_t size) __RENAME(strncpy);
45#else
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
57#define __underlying_memcpy __builtin_memcpy
58#define __underlying_memmove __builtin_memmove
59#define __underlying_memset __builtin_memset
60#endif
61
62#define __underlying_memchr __builtin_memchr
63#define __underlying_memcmp __builtin_memcmp
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
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
87/*
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
90 * size, rather than struct size), but there remain some stragglers using
91 * type 0 that will be converted in the future.
92 */
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#else
97#define POS __pass_object_size(1)
98#define POS0 __pass_object_size(0)
99#endif
100
101#define __compiletime_lessthan(bounds, length) ( \
102 __builtin_constant_p((bounds) < (length)) && \
103 (bounds) < (length) \
104)
105
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 *
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 * +--------------------+--------------------+------------+
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 */
138__FORTIFY_INLINE __diagnose_as(__builtin_strncpy, 1, 2, 3)
139char *strncpy(char * const POS p, const char *q, __kernel_size_t size)
140{
141 const size_t p_size = __member_size(p);
142
143 if (__compiletime_lessthan(p_size, size))
144 __write_overflow();
145 if (p_size < size)
146 fortify_panic(name: __func__);
147 return __underlying_strncpy(p, q, size);
148}
149
150extern __kernel_size_t __real_strnlen(const char *, __kernel_size_t) __RENAME(strnlen);
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 */
161__FORTIFY_INLINE __kernel_size_t strnlen(const char * const POS p, __kernel_size_t maxlen)
162{
163 const size_t p_size = __member_size(p);
164 const size_t p_len = __compiletime_strlen(p);
165 size_t ret;
166
167 /* We can take compile-time actions when maxlen is const. */
168 if (__builtin_constant_p(maxlen) && p_len != SIZE_MAX) {
169 /* If p is const, we can use its compile-time-known len. */
170 if (maxlen >= p_size)
171 return p_len;
172 }
173
174 /* Do not check characters beyond the end of p. */
175 ret = __real_strnlen(p, maxlen < p_size ? maxlen : p_size);
176 if (p_size <= ret && maxlen != ret)
177 fortify_panic(name: __func__);
178 return ret;
179}
180
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 */
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 */
199#define strlen(p) \
200 __builtin_choose_expr(__is_constexpr(__builtin_strlen(p)), \
201 __builtin_strlen(p), __fortify_strlen(p))
202__FORTIFY_INLINE __diagnose_as(__builtin_strlen, 1)
203__kernel_size_t __fortify_strlen(const char * const POS p)
204{
205 const size_t p_size = __member_size(p);
206 __kernel_size_t ret;
207
208 /* Give up if we don't know how large p is. */
209 if (p_size == SIZE_MAX)
210 return __underlying_strlen(p);
211 ret = strnlen(p, maxlen: p_size);
212 if (p_size <= ret)
213 fortify_panic(name: __func__);
214 return ret;
215}
216
217/* Defined after fortified strlen() to reuse it. */
218extern size_t __real_strlcpy(char *, const char *, size_t) __RENAME(strlcpy);
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 */
237__FORTIFY_INLINE size_t strlcpy(char * const POS p, const char * const POS q, size_t size)
238{
239 const size_t p_size = __member_size(p);
240 const size_t q_size = __member_size(q);
241 size_t q_len; /* Full count of source string length. */
242 size_t len; /* Count of characters going into destination. */
243
244 if (p_size == SIZE_MAX && q_size == SIZE_MAX)
245 return __real_strlcpy(p, q, size);
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)
251 __write_overflow();
252 }
253 if (size) {
254 if (len >= p_size)
255 fortify_panic(name: __func__);
256 __underlying_memcpy(p, q, len);
257 p[len] = '\0';
258 }
259 return q_len;
260}
261
262/* Defined after fortified strnlen() to reuse it. */
263extern ssize_t __real_strscpy(char *, const char *, size_t) __RENAME(strscpy);
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 *
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
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 */
288__FORTIFY_INLINE ssize_t strscpy(char * const POS p, const char * const POS q, size_t size)
289{
290 /* Use string size rather than possible enclosing struct size. */
291 const size_t p_size = __member_size(p);
292 const size_t q_size = __member_size(q);
293 size_t len;
294
295 /* If we cannot get size of p and q default to call strscpy. */
296 if (p_size == SIZE_MAX && q_size == SIZE_MAX)
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 */
303 if (__compiletime_lessthan(p_size, size))
304 __write_overflow();
305
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
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(p: q, maxlen: 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(name: __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
343/* Defined after fortified strlen() to reuse it. */
344extern 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
370size_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, maxlen: 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(name: __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(name: __func__);
401 __underlying_memcpy(p + p_len, q, copy_len);
402 p[actual] = '\0';
403
404 return wanted;
405}
406
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)
424char *strcat(char * const POS p, const char *q)
425{
426 const size_t p_size = __member_size(p);
427
428 if (strlcat(p, q, avail: p_size) >= p_size)
429 fortify_panic(name: __func__);
430 return p;
431}
432
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. */
453__FORTIFY_INLINE __diagnose_as(__builtin_strncat, 1, 2, 3)
454char *strncat(char * const POS p, const char * const POS q, __kernel_size_t count)
455{
456 const size_t p_size = __member_size(p);
457 const size_t q_size = __member_size(q);
458 size_t p_len, copy_len;
459
460 if (p_size == SIZE_MAX && q_size == SIZE_MAX)
461 return __underlying_strncat(p, q, count);
462 p_len = strlen(p);
463 copy_len = strnlen(p: q, maxlen: count);
464 if (p_size < p_len + copy_len + 1)
465 fortify_panic(name: __func__);
466 __underlying_memcpy(p + p_len, q, copy_len);
467 p[p_len + copy_len] = '\0';
468 return p;
469}
470
471__FORTIFY_INLINE void fortify_memset_chk(__kernel_size_t size,
472 const size_t p_size,
473 const size_t p_size_field)
474{
475 if (__builtin_constant_p(size)) {
476 /*
477 * Length argument is a constant expression, so we
478 * can perform compile-time bounds checking where
479 * buffer sizes are also known at compile time.
480 */
481
482 /* Error when size is larger than enclosing struct. */
483 if (__compiletime_lessthan(p_size_field, p_size) &&
484 __compiletime_lessthan(p_size, size))
485 __write_overflow();
486
487 /* Warn when write size is larger than dest field. */
488 if (__compiletime_lessthan(p_size_field, size))
489 __write_overflow_field(avail: p_size_field, wanted: 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.
502 * (The SIZE_MAX test is to optimize away checks where the buffer
503 * lengths are unknown.)
504 */
505 if (p_size != SIZE_MAX && p_size < size)
506 fortify_panic(name: "memset");
507}
508
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/*
516 * __struct_size() vs __member_size() must be captured here to avoid
517 * evaluating argument side-effects further into the macro layers.
518 */
519#ifndef CONFIG_KMSAN
520#define memset(p, c, s) __fortify_memset_chk(p, c, s, \
521 __struct_size(p), __member_size(p))
522#endif
523
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 */
555__FORTIFY_INLINE bool fortify_memcpy_chk(__kernel_size_t size,
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)
561{
562 if (__builtin_constant_p(size)) {
563 /*
564 * Length argument is a constant expression, so we
565 * can perform compile-time bounds checking where
566 * buffer sizes are also known at compile time.
567 */
568
569 /* Error when size is larger than enclosing struct. */
570 if (__compiletime_lessthan(p_size_field, p_size) &&
571 __compiletime_lessthan(p_size, size))
572 __write_overflow();
573 if (__compiletime_lessthan(q_size_field, q_size) &&
574 __compiletime_lessthan(q_size, size))
575 __read_overflow2();
576
577 /* Warn when write size argument larger than dest field. */
578 if (__compiletime_lessthan(p_size_field, size))
579 __write_overflow_field(avail: p_size_field, wanted: 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 */
585 if ((IS_ENABLED(KBUILD_EXTRA_WARN1) ||
586 __compiletime_lessthan(p_size_field, size)) &&
587 __compiletime_lessthan(q_size_field, size))
588 __read_overflow2_field(avail: q_size_field, wanted: size);
589 }
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.
601 * (The SIZE_MAX test is to optimize away checks where the buffer
602 * lengths are unknown.)
603 */
604 if ((p_size != SIZE_MAX && p_size < size) ||
605 (q_size != SIZE_MAX && q_size < size))
606 fortify_panic(name: func);
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 *
615 * The implementation of __builtin_*object_size() behaves
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;
628}
629
630#define __fortify_memcpy_chk(p, q, size, p_size, q_size, \
631 p_size_field, q_size_field, op) ({ \
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), \
640 #op ": detected field-spanning write (size %zu) of single %s (size %zu)\n", \
641 __fortify_size, \
642 "field \"" #p "\" at " FILE_LINE, \
643 __p_size_field); \
644 __underlying_##op(p, q, __fortify_size); \
645})
646
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
685/*
686 * __struct_size() vs __member_size() must be captured here to avoid
687 * evaluating argument side-effects further into the macro layers.
688 */
689#define memcpy(p, q, s) __fortify_memcpy_chk(p, q, s, \
690 __struct_size(p), __struct_size(q), \
691 __member_size(p), __member_size(q), \
692 memcpy)
693#define memmove(p, q, s) __fortify_memcpy_chk(p, q, s, \
694 __struct_size(p), __struct_size(q), \
695 __member_size(p), __member_size(q), \
696 memmove)
697
698extern void *__real_memscan(void *, int, __kernel_size_t) __RENAME(memscan);
699__FORTIFY_INLINE void *memscan(void * const POS0 p, int c, __kernel_size_t size)
700{
701 const size_t p_size = __struct_size(p);
702
703 if (__compiletime_lessthan(p_size, size))
704 __read_overflow();
705 if (p_size < size)
706 fortify_panic(name: __func__);
707 return __real_memscan(p, c, size);
708}
709
710__FORTIFY_INLINE __diagnose_as(__builtin_memcmp, 1, 2, 3)
711int memcmp(const void * const POS0 p, const void * const POS0 q, __kernel_size_t size)
712{
713 const size_t p_size = __struct_size(p);
714 const size_t q_size = __struct_size(q);
715
716 if (__builtin_constant_p(size)) {
717 if (__compiletime_lessthan(p_size, size))
718 __read_overflow();
719 if (__compiletime_lessthan(q_size, size))
720 __read_overflow2();
721 }
722 if (p_size < size || q_size < size)
723 fortify_panic(name: __func__);
724 return __underlying_memcmp(p, q, size);
725}
726
727__FORTIFY_INLINE __diagnose_as(__builtin_memchr, 1, 2, 3)
728void *memchr(const void * const POS0 p, int c, __kernel_size_t size)
729{
730 const size_t p_size = __struct_size(p);
731
732 if (__compiletime_lessthan(p_size, size))
733 __read_overflow();
734 if (p_size < size)
735 fortify_panic(name: __func__);
736 return __underlying_memchr(p, c, size);
737}
738
739void *__real_memchr_inv(const void *s, int c, size_t n) __RENAME(memchr_inv);
740__FORTIFY_INLINE void *memchr_inv(const void * const POS0 p, int c, size_t size)
741{
742 const size_t p_size = __struct_size(p);
743
744 if (__compiletime_lessthan(p_size, size))
745 __read_overflow();
746 if (p_size < size)
747 fortify_panic(name: __func__);
748 return __real_memchr_inv(s: p, c, n: size);
749}
750
751extern void *__real_kmemdup(const void *src, size_t len, gfp_t gfp) __RENAME(kmemdup)
752 __realloc_size(2);
753__FORTIFY_INLINE void *kmemdup(const void * const POS0 p, size_t size, gfp_t gfp)
754{
755 const size_t p_size = __struct_size(p);
756
757 if (__compiletime_lessthan(p_size, size))
758 __read_overflow();
759 if (p_size < size)
760 fortify_panic(name: __func__);
761 return __real_kmemdup(src: p, len: size, gfp);
762}
763
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 */
778/* Defined after fortified strlen to reuse it. */
779__FORTIFY_INLINE __diagnose_as(__builtin_strcpy, 1, 2)
780char *strcpy(char * const POS p, const char * const POS q)
781{
782 const size_t p_size = __member_size(p);
783 const size_t q_size = __member_size(q);
784 size_t size;
785
786 /* If neither buffer size is known, immediately give up. */
787 if (__builtin_constant_p(p_size) &&
788 __builtin_constant_p(q_size) &&
789 p_size == SIZE_MAX && q_size == SIZE_MAX)
790 return __underlying_strcpy(p, q);
791 size = strlen(q) + 1;
792 /* Compile-time check for const size overflow. */
793 if (__compiletime_lessthan(p_size, size))
794 __write_overflow();
795 /* Run-time check for dynamic size overflow. */
796 if (p_size < size)
797 fortify_panic(name: __func__);
798 __underlying_memcpy(p, q, size);
799 return p;
800}
801
802/* Don't use these outside the FORITFY_SOURCE implementation */
803#undef __underlying_memchr
804#undef __underlying_memcmp
805#undef __underlying_strcat
806#undef __underlying_strcpy
807#undef __underlying_strlen
808#undef __underlying_strncat
809#undef __underlying_strncpy
810
811#undef POS
812#undef POS0
813
814#endif /* _LINUX_FORTIFY_STRING_H_ */
815

source code of linux/include/linux/fortify-string.h