Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
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linux
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
12#define FORTIFY_REASON_DIR(r) ((r) & 1)
13#define FORTIFY_REASON_FUNC(r) ((r) >> 1)
14#define FORTIFY_REASON(func, write) ((func) << 1 | (write))
15
16/* Overridden by KUnit tests. */
17#ifndef fortify_panic
18# define fortify_panic(func, write, avail, size, retfail) \
19 __fortify_panic(FORTIFY_REASON(func, write), avail, size)
20#endif
21#ifndef fortify_warn_once
22# define fortify_warn_once(x...) WARN_ONCE(x)
23#endif
24
25#define FORTIFY_READ 0
26#define FORTIFY_WRITE 1
27
28#define EACH_FORTIFY_FUNC(macro) \
29 macro(strncpy), \
30 macro(strnlen), \
31 macro(strlen), \
32 macro(strscpy), \
33 macro(strlcat), \
34 macro(strcat), \
35 macro(strncat), \
36 macro(memset), \
37 macro(memcpy), \
38 macro(memmove), \
39 macro(memscan), \
40 macro(memcmp), \
41 macro(memchr), \
42 macro(memchr_inv), \
43 macro(kmemdup), \
44 macro(strcpy), \
45 macro(UNKNOWN),
46
47#define MAKE_FORTIFY_FUNC(func) FORTIFY_FUNC_##func
48
49enum fortify_func {
50 EACH_FORTIFY_FUNC(MAKE_FORTIFY_FUNC)
51};
52
53void __fortify_report(const u8 reason, const size_t avail, const size_t size);
54void __fortify_panic(const u8 reason, const size_t avail, const size_t size) __cold __noreturn;
55void __read_overflow(void) __compiletime_error("detected read beyond size of object (1st parameter)");
56void __read_overflow2(void) __compiletime_error("detected read beyond size of object (2nd parameter)");
57void __read_overflow2_field(size_t avail, size_t wanted) __compiletime_warning("detected read beyond size of field (2nd parameter); maybe use struct_group()?");
58void __write_overflow(void) __compiletime_error("detected write beyond size of object (1st parameter)");
59void __write_overflow_field(size_t avail, size_t wanted) __compiletime_warning("detected write beyond size of field (1st parameter); maybe use struct_group()?");
60
61#define __compiletime_strlen(p) \
62({ \
63 char *__p = (char *)(p); \
64 size_t __ret = SIZE_MAX; \
65 const size_t __p_size = __member_size(p); \
66 if (__p_size != SIZE_MAX && \
67 __builtin_constant_p(*__p)) { \
68 size_t __p_len = __p_size - 1; \
69 if (__builtin_constant_p(__p[__p_len]) && \
70 __p[__p_len] == '\0') \
71 __ret = __builtin_strlen(__p); \
72 } \
73 __ret; \
74})
75
76#if defined(__SANITIZE_ADDRESS__)
77
78#if !defined(CONFIG_CC_HAS_KASAN_MEMINTRINSIC_PREFIX) && !defined(CONFIG_GENERIC_ENTRY)
79extern void *__underlying_memset(void *p, int c, __kernel_size_t size) __RENAME(memset);
80extern void *__underlying_memmove(void *p, const void *q, __kernel_size_t size) __RENAME(memmove);
81extern void *__underlying_memcpy(void *p, const void *q, __kernel_size_t size) __RENAME(memcpy);
82#elif defined(CONFIG_KASAN_GENERIC)
83extern void *__underlying_memset(void *p, int c, __kernel_size_t size) __RENAME(__asan_memset);
84extern void *__underlying_memmove(void *p, const void *q, __kernel_size_t size) __RENAME(__asan_memmove);
85extern void *__underlying_memcpy(void *p, const void *q, __kernel_size_t size) __RENAME(__asan_memcpy);
86#else /* CONFIG_KASAN_SW_TAGS */
87extern void *__underlying_memset(void *p, int c, __kernel_size_t size) __RENAME(__hwasan_memset);
88extern void *__underlying_memmove(void *p, const void *q, __kernel_size_t size) __RENAME(__hwasan_memmove);
89extern void *__underlying_memcpy(void *p, const void *q, __kernel_size_t size) __RENAME(__hwasan_memcpy);
90#endif
91
92extern void *__underlying_memchr(const void *p, int c, __kernel_size_t size) __RENAME(memchr);
93extern int __underlying_memcmp(const void *p, const void *q, __kernel_size_t size) __RENAME(memcmp);
94extern char *__underlying_strcat(char *p, const char *q) __RENAME(strcat);
95extern char *__underlying_strcpy(char *p, const char *q) __RENAME(strcpy);
96extern __kernel_size_t __underlying_strlen(const char *p) __RENAME(strlen);
97extern char *__underlying_strncat(char *p, const char *q, __kernel_size_t count) __RENAME(strncat);
98extern char *__underlying_strncpy(char *p, const char *q, __kernel_size_t size) __RENAME(strncpy);
99
100#else
101
102#if defined(__SANITIZE_MEMORY__)
103/*
104 * For KMSAN builds all memcpy/memset/memmove calls should be replaced by the
105 * corresponding __msan_XXX functions.
106 */
107#include <linux/kmsan_string.h>
108#define __underlying_memcpy __msan_memcpy
109#define __underlying_memmove __msan_memmove
110#define __underlying_memset __msan_memset
111#else
112#define __underlying_memcpy __builtin_memcpy
113#define __underlying_memmove __builtin_memmove
114#define __underlying_memset __builtin_memset
115#endif
116
117#define __underlying_memchr __builtin_memchr
118#define __underlying_memcmp __builtin_memcmp
119#define __underlying_strcat __builtin_strcat
120#define __underlying_strcpy __builtin_strcpy
121#define __underlying_strlen __builtin_strlen
122#define __underlying_strncat __builtin_strncat
123#define __underlying_strncpy __builtin_strncpy
124
125#endif
126
127/**
128 * unsafe_memcpy - memcpy implementation with no FORTIFY bounds checking
129 *
130 * @dst: Destination memory address to write to
131 * @src: Source memory address to read from
132 * @bytes: How many bytes to write to @dst from @src
133 * @justification: Free-form text or comment describing why the use is needed
134 *
135 * This should be used for corner cases where the compiler cannot do the
136 * right thing, or during transitions between APIs, etc. It should be used
137 * very rarely, and includes a place for justification detailing where bounds
138 * checking has happened, and why existing solutions cannot be employed.
139 */
140#define unsafe_memcpy(dst, src, bytes, justification) \
141 __underlying_memcpy(dst, src, bytes)
142
143/*
144 * Clang's use of __builtin_*object_size() within inlines needs hinting via
145 * __pass_*object_size(). The preference is to only ever use type 1 (member
146 * size, rather than struct size), but there remain some stragglers using
147 * type 0 that will be converted in the future.
148 */
149#if __has_builtin(__builtin_dynamic_object_size)
150#define POS __pass_dynamic_object_size(1)
151#define POS0 __pass_dynamic_object_size(0)
152#else
153#define POS __pass_object_size(1)
154#define POS0 __pass_object_size(0)
155#endif
156
157#define __compiletime_lessthan(bounds, length) ( \
158 __builtin_constant_p((bounds) < (length)) && \
159 (bounds) < (length) \
160)
161
162/**
163 * strncpy - Copy a string to memory with non-guaranteed NUL padding
164 *
165 * @p: pointer to destination of copy
166 * @q: pointer to NUL-terminated source string to copy
167 * @size: bytes to write at @p
168 *
169 * If strlen(@q) >= @size, the copy of @q will stop after @size bytes,
170 * and @p will NOT be NUL-terminated
171 *
172 * If strlen(@q) < @size, following the copy of @q, trailing NUL bytes
173 * will be written to @p until @size total bytes have been written.
174 *
175 * Do not use this function. While FORTIFY_SOURCE tries to avoid
176 * over-reads of @q, it cannot defend against writing unterminated
177 * results to @p. Using strncpy() remains ambiguous and fragile.
178 * Instead, please choose an alternative, so that the expectation
179 * of @p's contents is unambiguous:
180 *
181 * +--------------------+--------------------+------------+
182 * | **p** needs to be: | padded to **size** | not padded |
183 * +====================+====================+============+
184 * | NUL-terminated | strscpy_pad() | strscpy() |
185 * +--------------------+--------------------+------------+
186 * | not NUL-terminated | strtomem_pad() | strtomem() |
187 * +--------------------+--------------------+------------+
188 *
189 * Note strscpy*()'s differing return values for detecting truncation,
190 * and strtomem*()'s expectation that the destination is marked with
191 * __nonstring when it is a character array.
192 *
193 */
194__FORTIFY_INLINE __diagnose_as(__builtin_strncpy, 1, 2, 3)
195char *strncpy(char * const POS p, const char *q, __kernel_size_t size)
196{
197 const size_t p_size = __member_size(p);
198
199 if (__compiletime_lessthan(p_size, size))
200 __write_overflow();
201 if (p_size < size)
202 fortify_panic(FORTIFY_FUNC_strncpy, FORTIFY_WRITE, p_size, size, p);
203 return __underlying_strncpy(p, q, size);
204}
205
206extern __kernel_size_t __real_strnlen(const char *, __kernel_size_t) __RENAME(strnlen);
207/**
208 * strnlen - Return bounded count of characters in a NUL-terminated string
209 *
210 * @p: pointer to NUL-terminated string to count.
211 * @maxlen: maximum number of characters to count.
212 *
213 * Returns number of characters in @p (NOT including the final NUL), or
214 * @maxlen, if no NUL has been found up to there.
215 *
216 */
217__FORTIFY_INLINE __kernel_size_t strnlen(const char * const POS p, __kernel_size_t maxlen)
218{
219 const size_t p_size = __member_size(p);
220 const size_t p_len = __compiletime_strlen(p);
221 size_t ret;
222
223 /* We can take compile-time actions when maxlen is const. */
224 if (__builtin_constant_p(maxlen) && p_len != SIZE_MAX) {
225 /* If p is const, we can use its compile-time-known len. */
226 if (maxlen >= p_size)
227 return p_len;
228 }
229
230 /* Do not check characters beyond the end of p. */
231 ret = __real_strnlen(p, maxlen < p_size ? maxlen : p_size);
232 if (p_size <= ret && maxlen != ret)
233 fortify_panic(FORTIFY_FUNC_strnlen, FORTIFY_READ, p_size, ret + 1, ret);
234 return ret;
235}
236
237/*
238 * Defined after fortified strnlen to reuse it. However, it must still be
239 * possible for strlen() to be used on compile-time strings for use in
240 * static initializers (i.e. as a constant expression).
241 */
242/**
243 * strlen - Return count of characters in a NUL-terminated string
244 *
245 * @p: pointer to NUL-terminated string to count.
246 *
247 * Do not use this function unless the string length is known at
248 * compile-time. When @p is unterminated, this function may crash
249 * or return unexpected counts that could lead to memory content
250 * exposures. Prefer strnlen().
251 *
252 * Returns number of characters in @p (NOT including the final NUL).
253 *
254 */
255#define strlen(p) \
256 __builtin_choose_expr(__is_constexpr(__builtin_strlen(p)), \
257 __builtin_strlen(p), __fortify_strlen(p))
258__FORTIFY_INLINE __diagnose_as(__builtin_strlen, 1)
259__kernel_size_t __fortify_strlen(const char * const POS p)
260{
261 const size_t p_size = __member_size(p);
262 __kernel_size_t ret;
263
264 /* Give up if we don't know how large p is. */
265 if (p_size == SIZE_MAX)
266 return __underlying_strlen(p);
267 ret = strnlen(p, p_size);
268 if (p_size <= ret)
269 fortify_panic(FORTIFY_FUNC_strlen, FORTIFY_READ, p_size, ret + 1, ret);
270 return ret;
271}
272
273/* Defined after fortified strnlen() to reuse it. */
274extern ssize_t __real_strscpy(char *, const char *, size_t) __RENAME(sized_strscpy);
275__FORTIFY_INLINE ssize_t sized_strscpy(char * const POS p, const char * const POS q, size_t size)
276{
277 /* Use string size rather than possible enclosing struct size. */
278 const size_t p_size = __member_size(p);
279 const size_t q_size = __member_size(q);
280 size_t len;
281
282 /* If we cannot get size of p and q default to call strscpy. */
283 if (p_size == SIZE_MAX && q_size == SIZE_MAX)
284 return __real_strscpy(p, q, size);
285
286 /*
287 * If size can be known at compile time and is greater than
288 * p_size, generate a compile time write overflow error.
289 */
290 if (__compiletime_lessthan(p_size, size))
291 __write_overflow();
292
293 /* Short-circuit for compile-time known-safe lengths. */
294 if (__compiletime_lessthan(p_size, SIZE_MAX)) {
295 len = __compiletime_strlen(q);
296
297 if (len < SIZE_MAX && __compiletime_lessthan(len, size)) {
298 __underlying_memcpy(p, q, len + 1);
299 return len;
300 }
301 }
302
303 /*
304 * This call protects from read overflow, because len will default to q
305 * length if it smaller than size.
306 */
307 len = strnlen(q, size);
308 /*
309 * If len equals size, we will copy only size bytes which leads to
310 * -E2BIG being returned.
311 * Otherwise we will copy len + 1 because of the final '\O'.
312 */
313 len = len == size ? size : len + 1;
314
315 /*
316 * Generate a runtime write overflow error if len is greater than
317 * p_size.
318 */
319 if (p_size < len)
320 fortify_panic(FORTIFY_FUNC_strscpy, FORTIFY_WRITE, p_size, len, -E2BIG);
321
322 /*
323 * We can now safely call vanilla strscpy because we are protected from:
324 * 1. Read overflow thanks to call to strnlen().
325 * 2. Write overflow thanks to above ifs.
326 */
327 return __real_strscpy(p, q, len);
328}
329
330/* Defined after fortified strlen() to reuse it. */
331extern size_t __real_strlcat(char *p, const char *q, size_t avail) __RENAME(strlcat);
332/**
333 * strlcat - Append a string to an existing string
334 *
335 * @p: pointer to %NUL-terminated string to append to
336 * @q: pointer to %NUL-terminated string to append from
337 * @avail: Maximum bytes available in @p
338 *
339 * Appends %NUL-terminated string @q after the %NUL-terminated
340 * string at @p, but will not write beyond @avail bytes total,
341 * potentially truncating the copy from @q. @p will stay
342 * %NUL-terminated only if a %NUL already existed within
343 * the @avail bytes of @p. If so, the resulting number of
344 * bytes copied from @q will be at most "@avail - strlen(@p) - 1".
345 *
346 * Do not use this function. While FORTIFY_SOURCE tries to avoid
347 * read and write overflows, this is only possible when the sizes
348 * of @p and @q are known to the compiler. Prefer building the
349 * string with formatting, via scnprintf(), seq_buf, or similar.
350 *
351 * Returns total bytes that _would_ have been contained by @p
352 * regardless of truncation, similar to snprintf(). If return
353 * value is >= @avail, the string has been truncated.
354 *
355 */
356__FORTIFY_INLINE
357size_t strlcat(char * const POS p, const char * const POS q, size_t avail)
358{
359 const size_t p_size = __member_size(p);
360 const size_t q_size = __member_size(q);
361 size_t p_len, copy_len;
362 size_t actual, wanted;
363
364 /* Give up immediately if both buffer sizes are unknown. */
365 if (p_size == SIZE_MAX && q_size == SIZE_MAX)
366 return __real_strlcat(p, q, avail);
367
368 p_len = strnlen(p, avail);
369 copy_len = strlen(q);
370 wanted = actual = p_len + copy_len;
371
372 /* Cannot append any more: report truncation. */
373 if (avail <= p_len)
374 return wanted;
375
376 /* Give up if string is already overflowed. */
377 if (p_size <= p_len)
378 fortify_panic(FORTIFY_FUNC_strlcat, FORTIFY_READ, p_size, p_len + 1, wanted);
379
380 if (actual >= avail) {
381 copy_len = avail - p_len - 1;
382 actual = p_len + copy_len;
383 }
384
385 /* Give up if copy will overflow. */
386 if (p_size <= actual)
387 fortify_panic(FORTIFY_FUNC_strlcat, FORTIFY_WRITE, p_size, actual + 1, wanted);
388 __underlying_memcpy(p + p_len, q, copy_len);
389 p[actual] = '\0';
390
391 return wanted;
392}
393
394/* Defined after fortified strlcat() to reuse it. */
395/**
396 * strcat - Append a string to an existing string
397 *
398 * @p: pointer to NUL-terminated string to append to
399 * @q: pointer to NUL-terminated source string to append from
400 *
401 * Do not use this function. While FORTIFY_SOURCE tries to avoid
402 * read and write overflows, this is only possible when the
403 * destination buffer size is known to the compiler. Prefer
404 * building the string with formatting, via scnprintf() or similar.
405 * At the very least, use strncat().
406 *
407 * Returns @p.
408 *
409 */
410__FORTIFY_INLINE __diagnose_as(__builtin_strcat, 1, 2)
411char *strcat(char * const POS p, const char *q)
412{
413 const size_t p_size = __member_size(p);
414 const size_t wanted = strlcat(p, q, p_size);
415
416 if (p_size <= wanted)
417 fortify_panic(FORTIFY_FUNC_strcat, FORTIFY_WRITE, p_size, wanted + 1, p);
418 return p;
419}
420
421/**
422 * strncat - Append a string to an existing string
423 *
424 * @p: pointer to NUL-terminated string to append to
425 * @q: pointer to source string to append from
426 * @count: Maximum bytes to read from @q
427 *
428 * Appends at most @count bytes from @q (stopping at the first
429 * NUL byte) after the NUL-terminated string at @p. @p will be
430 * NUL-terminated.
431 *
432 * Do not use this function. While FORTIFY_SOURCE tries to avoid
433 * read and write overflows, this is only possible when the sizes
434 * of @p and @q are known to the compiler. Prefer building the
435 * string with formatting, via scnprintf() or similar.
436 *
437 * Returns @p.
438 *
439 */
440/* Defined after fortified strlen() and strnlen() to reuse them. */
441__FORTIFY_INLINE __diagnose_as(__builtin_strncat, 1, 2, 3)
442char *strncat(char * const POS p, const char * const POS q, __kernel_size_t count)
443{
444 const size_t p_size = __member_size(p);
445 const size_t q_size = __member_size(q);
446 size_t p_len, copy_len, total;
447
448 if (p_size == SIZE_MAX && q_size == SIZE_MAX)
449 return __underlying_strncat(p, q, count);
450 p_len = strlen(p);
451 copy_len = strnlen(q, count);
452 total = p_len + copy_len + 1;
453 if (p_size < total)
454 fortify_panic(FORTIFY_FUNC_strncat, FORTIFY_WRITE, p_size, total, p);
455 __underlying_memcpy(p + p_len, q, copy_len);
456 p[p_len + copy_len] = '\0';
457 return p;
458}
459
460__FORTIFY_INLINE bool fortify_memset_chk(__kernel_size_t size,
461 const size_t p_size,
462 const size_t p_size_field)
463{
464 if (__builtin_constant_p(size)) {
465 /*
466 * Length argument is a constant expression, so we
467 * can perform compile-time bounds checking where
468 * buffer sizes are also known at compile time.
469 */
470
471 /* Error when size is larger than enclosing struct. */
472 if (__compiletime_lessthan(p_size_field, p_size) &&
473 __compiletime_lessthan(p_size, size))
474 __write_overflow();
475
476 /* Warn when write size is larger than dest field. */
477 if (__compiletime_lessthan(p_size_field, size))
478 __write_overflow_field(p_size_field, size);
479 }
480 /*
481 * At this point, length argument may not be a constant expression,
482 * so run-time bounds checking can be done where buffer sizes are
483 * known. (This is not an "else" because the above checks may only
484 * be compile-time warnings, and we want to still warn for run-time
485 * overflows.)
486 */
487
488 /*
489 * Always stop accesses beyond the struct that contains the
490 * field, when the buffer's remaining size is known.
491 * (The SIZE_MAX test is to optimize away checks where the buffer
492 * lengths are unknown.)
493 */
494 if (p_size != SIZE_MAX && p_size < size)
495 fortify_panic(FORTIFY_FUNC_memset, FORTIFY_WRITE, p_size, size, true);
496 return false;
497}
498
499#define __fortify_memset_chk(p, c, size, p_size, p_size_field) ({ \
500 size_t __fortify_size = (size_t)(size); \
501 fortify_memset_chk(__fortify_size, p_size, p_size_field), \
502 __underlying_memset(p, c, __fortify_size); \
503})
504
505/*
506 * __struct_size() vs __member_size() must be captured here to avoid
507 * evaluating argument side-effects further into the macro layers.
508 */
509#ifndef CONFIG_KMSAN
510#define memset(p, c, s) __fortify_memset_chk(p, c, s, \
511 __struct_size(p), __member_size(p))
512#endif
513
514/*
515 * To make sure the compiler can enforce protection against buffer overflows,
516 * memcpy(), memmove(), and memset() must not be used beyond individual
517 * struct members. If you need to copy across multiple members, please use
518 * struct_group() to create a named mirror of an anonymous struct union.
519 * (e.g. see struct sk_buff.) Read overflow checking is currently only
520 * done when a write overflow is also present, or when building with W=1.
521 *
522 * Mitigation coverage matrix
523 * Bounds checking at:
524 * +-------+-------+-------+-------+
525 * | Compile time | Run time |
526 * memcpy() argument sizes: | write | read | write | read |
527 * dest source length +-------+-------+-------+-------+
528 * memcpy(known, known, constant) | y | y | n/a | n/a |
529 * memcpy(known, unknown, constant) | y | n | n/a | V |
530 * memcpy(known, known, dynamic) | n | n | B | B |
531 * memcpy(known, unknown, dynamic) | n | n | B | V |
532 * memcpy(unknown, known, constant) | n | y | V | n/a |
533 * memcpy(unknown, unknown, constant) | n | n | V | V |
534 * memcpy(unknown, known, dynamic) | n | n | V | B |
535 * memcpy(unknown, unknown, dynamic) | n | n | V | V |
536 * +-------+-------+-------+-------+
537 *
538 * y = perform deterministic compile-time bounds checking
539 * n = cannot perform deterministic compile-time bounds checking
540 * n/a = no run-time bounds checking needed since compile-time deterministic
541 * B = can perform run-time bounds checking (currently unimplemented)
542 * V = vulnerable to run-time overflow (will need refactoring to solve)
543 *
544 */
545__FORTIFY_INLINE bool fortify_memcpy_chk(__kernel_size_t size,
546 const size_t p_size,
547 const size_t q_size,
548 const size_t p_size_field,
549 const size_t q_size_field,
550 const u8 func)
551{
552 if (__builtin_constant_p(size)) {
553 /*
554 * Length argument is a constant expression, so we
555 * can perform compile-time bounds checking where
556 * buffer sizes are also known at compile time.
557 */
558
559 /* Error when size is larger than enclosing struct. */
560 if (__compiletime_lessthan(p_size_field, p_size) &&
561 __compiletime_lessthan(p_size, size))
562 __write_overflow();
563 if (__compiletime_lessthan(q_size_field, q_size) &&
564 __compiletime_lessthan(q_size, size))
565 __read_overflow2();
566
567 /* Warn when write size argument larger than dest field. */
568 if (__compiletime_lessthan(p_size_field, size))
569 __write_overflow_field(p_size_field, size);
570 /*
571 * Warn for source field over-read when building with W=1
572 * or when an over-write happened, so both can be fixed at
573 * the same time.
574 */
575 if ((IS_ENABLED(KBUILD_EXTRA_WARN1) ||
576 __compiletime_lessthan(p_size_field, size)) &&
577 __compiletime_lessthan(q_size_field, size))
578 __read_overflow2_field(q_size_field, size);
579 }
580 /*
581 * At this point, length argument may not be a constant expression,
582 * so run-time bounds checking can be done where buffer sizes are
583 * known. (This is not an "else" because the above checks may only
584 * be compile-time warnings, and we want to still warn for run-time
585 * overflows.)
586 */
587
588 /*
589 * Always stop accesses beyond the struct that contains the
590 * field, when the buffer's remaining size is known.
591 * (The SIZE_MAX test is to optimize away checks where the buffer
592 * lengths are unknown.)
593 */
594 if (p_size != SIZE_MAX && p_size < size)
595 fortify_panic(func, FORTIFY_WRITE, p_size, size, true);
596 else if (q_size != SIZE_MAX && q_size < size)
597 fortify_panic(func, FORTIFY_READ, q_size, size, true);
598
599 /*
600 * Warn when writing beyond destination field size.
601 *
602 * Note the implementation of __builtin_*object_size() behaves
603 * like sizeof() when not directly referencing a flexible
604 * array member, which means there will be many bounds checks
605 * that will appear at run-time, without a way for them to be
606 * detected at compile-time (as can be done when the destination
607 * is specifically the flexible array member).
608 * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101832
609 */
610 if (p_size_field != SIZE_MAX &&
611 p_size != p_size_field && p_size_field < size)
612 return true;
613
614 return false;
615}
616
617/*
618 * To work around what seems to be an optimizer bug, the macro arguments
619 * need to have const copies or the values end up changed by the time they
620 * reach fortify_warn_once(). See commit 6f7630b1b5bc ("fortify: Capture
621 * __bos() results in const temp vars") for more details.
622 */
623#define __fortify_memcpy_chk(p, q, size, p_size, q_size, \
624 p_size_field, q_size_field, op) ({ \
625 const size_t __fortify_size = (size_t)(size); \
626 const size_t __p_size = (p_size); \
627 const size_t __q_size = (q_size); \
628 const size_t __p_size_field = (p_size_field); \
629 const size_t __q_size_field = (q_size_field); \
630 /* Keep a mutable version of the size for the final copy. */ \
631 size_t __copy_size = __fortify_size; \
632 fortify_warn_once(fortify_memcpy_chk(__fortify_size, __p_size, \
633 __q_size, __p_size_field, \
634 __q_size_field, FORTIFY_FUNC_ ##op), \
635 #op ": detected field-spanning write (size %zu) of single %s (size %zu)\n", \
636 __fortify_size, \
637 "field \"" #p "\" at " FILE_LINE, \
638 __p_size_field); \
639 /* Hide only the run-time size from value range tracking to */ \
640 /* silence compile-time false positive bounds warnings. */ \
641 if (!__builtin_constant_p(__copy_size)) \
642 OPTIMIZER_HIDE_VAR(__copy_size); \
643 __underlying_##op(p, q, __copy_size); \
644})
645
646/*
647 * Notes about compile-time buffer size detection:
648 *
649 * With these types...
650 *
651 * struct middle {
652 * u16 a;
653 * u8 middle_buf[16];
654 * int b;
655 * };
656 * struct end {
657 * u16 a;
658 * u8 end_buf[16];
659 * };
660 * struct flex {
661 * int a;
662 * u8 flex_buf[];
663 * };
664 *
665 * void func(TYPE *ptr) { ... }
666 *
667 * Cases where destination size cannot be currently detected:
668 * - the size of ptr's object (seemingly by design, gcc & clang fail):
669 * __builtin_object_size(ptr, 1) == SIZE_MAX
670 * - the size of flexible arrays in ptr's obj (by design, dynamic size):
671 * __builtin_object_size(ptr->flex_buf, 1) == SIZE_MAX
672 * - the size of ANY array at the end of ptr's obj (gcc and clang bug):
673 * __builtin_object_size(ptr->end_buf, 1) == SIZE_MAX
674 * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101836
675 *
676 * Cases where destination size is currently detected:
677 * - the size of non-array members within ptr's object:
678 * __builtin_object_size(ptr->a, 1) == 2
679 * - the size of non-flexible-array in the middle of ptr's obj:
680 * __builtin_object_size(ptr->middle_buf, 1) == 16
681 *
682 */
683
684/*
685 * __struct_size() vs __member_size() must be captured here to avoid
686 * evaluating argument side-effects further into the macro layers.
687 */
688#define memcpy(p, q, s) __fortify_memcpy_chk(p, q, s, \
689 __struct_size(p), __struct_size(q), \
690 __member_size(p), __member_size(q), \
691 memcpy)
692#define memmove(p, q, s) __fortify_memcpy_chk(p, q, s, \
693 __struct_size(p), __struct_size(q), \
694 __member_size(p), __member_size(q), \
695 memmove)
696
697extern void *__real_memscan(void *, int, __kernel_size_t) __RENAME(memscan);
698__FORTIFY_INLINE void *memscan(void * const POS0 p, int c, __kernel_size_t size)
699{
700 const size_t p_size = __struct_size(p);
701
702 if (__compiletime_lessthan(p_size, size))
703 __read_overflow();
704 if (p_size < size)
705 fortify_panic(FORTIFY_FUNC_memscan, FORTIFY_READ, p_size, size, NULL);
706 return __real_memscan(p, c, size);
707}
708
709__FORTIFY_INLINE __diagnose_as(__builtin_memcmp, 1, 2, 3)
710int memcmp(const void * const POS0 p, const void * const POS0 q, __kernel_size_t size)
711{
712 const size_t p_size = __struct_size(p);
713 const size_t q_size = __struct_size(q);
714
715 if (__builtin_constant_p(size)) {
716 if (__compiletime_lessthan(p_size, size))
717 __read_overflow();
718 if (__compiletime_lessthan(q_size, size))
719 __read_overflow2();
720 }
721 if (p_size < size)
722 fortify_panic(FORTIFY_FUNC_memcmp, FORTIFY_READ, p_size, size, INT_MIN);
723 else if (q_size < size)
724 fortify_panic(FORTIFY_FUNC_memcmp, FORTIFY_READ, q_size, size, INT_MIN);
725 return __underlying_memcmp(p, q, size);
726}
727
728__FORTIFY_INLINE __diagnose_as(__builtin_memchr, 1, 2, 3)
729void *memchr(const void * const POS0 p, int c, __kernel_size_t size)
730{
731 const size_t p_size = __struct_size(p);
732
733 if (__compiletime_lessthan(p_size, size))
734 __read_overflow();
735 if (p_size < size)
736 fortify_panic(FORTIFY_FUNC_memchr, FORTIFY_READ, p_size, size, NULL);
737 return __underlying_memchr(p, c, size);
738}
739
740void *__real_memchr_inv(const void *s, int c, size_t n) __RENAME(memchr_inv);
741__FORTIFY_INLINE void *memchr_inv(const void * const POS0 p, int c, size_t size)
742{
743 const size_t p_size = __struct_size(p);
744
745 if (__compiletime_lessthan(p_size, size))
746 __read_overflow();
747 if (p_size < size)
748 fortify_panic(FORTIFY_FUNC_memchr_inv, FORTIFY_READ, p_size, size, NULL);
749 return __real_memchr_inv(p, c, size);
750}
751
752extern void *__real_kmemdup(const void *src, size_t len, gfp_t gfp) __RENAME(kmemdup_noprof)
753 __realloc_size(2);
754__FORTIFY_INLINE void *kmemdup_noprof(const void * const POS0 p, size_t size, gfp_t gfp)
755{
756 const size_t p_size = __struct_size(p);
757
758 if (__compiletime_lessthan(p_size, size))
759 __read_overflow();
760 if (p_size < size)
761 fortify_panic(FORTIFY_FUNC_kmemdup, FORTIFY_READ, p_size, size,
762 __real_kmemdup(p, 0, gfp));
763 return __real_kmemdup(p, size, gfp);
764}
765#define kmemdup(...) alloc_hooks(kmemdup_noprof(__VA_ARGS__))
766
767/**
768 * strcpy - Copy a string into another string buffer
769 *
770 * @p: pointer to destination of copy
771 * @q: pointer to NUL-terminated source string to copy
772 *
773 * Do not use this function. While FORTIFY_SOURCE tries to avoid
774 * overflows, this is only possible when the sizes of @q and @p are
775 * known to the compiler. Prefer strscpy(), though note its different
776 * return values for detecting truncation.
777 *
778 * Returns @p.
779 *
780 */
781/* Defined after fortified strlen to reuse it. */
782__FORTIFY_INLINE __diagnose_as(__builtin_strcpy, 1, 2)
783char *strcpy(char * const POS p, const char * const POS q)
784{
785 const size_t p_size = __member_size(p);
786 const size_t q_size = __member_size(q);
787 size_t size;
788
789 /* If neither buffer size is known, immediately give up. */
790 if (__builtin_constant_p(p_size) &&
791 __builtin_constant_p(q_size) &&
792 p_size == SIZE_MAX && q_size == SIZE_MAX)
793 return __underlying_strcpy(p, q);
794 size = strlen(q) + 1;
795 /* Compile-time check for const size overflow. */
796 if (__compiletime_lessthan(p_size, size))
797 __write_overflow();
798 /* Run-time check for dynamic size overflow. */
799 if (p_size < size)
800 fortify_panic(FORTIFY_FUNC_strcpy, FORTIFY_WRITE, p_size, size, p);
801 __underlying_memcpy(p, q, size);
802 return p;
803}
804
805/* Don't use these outside the FORITFY_SOURCE implementation */
806#undef __underlying_memchr
807#undef __underlying_memcmp
808#undef __underlying_strcat
809#undef __underlying_strcpy
810#undef __underlying_strlen
811#undef __underlying_strncat
812#undef __underlying_strncpy
813
814#undef POS
815#undef POS0
816
817#endif /* _LINUX_FORTIFY_STRING_H_ */