/* SPDX-License-Identifier: GPL-2.0 */ #ifndef _LINUX_FORTIFY_STRING_H_ #define _LINUX_FORTIFY_STRING_H_ #include <linux/bitfield.h> #include <linux/bug.h> #include <linux/const.h> #include <linux/limits.h> #define __FORTIFY_INLINE … #define __RENAME(x) … #define FORTIFY_REASON_DIR(r) … #define FORTIFY_REASON_FUNC(r) … #define FORTIFY_REASON(func, write) … /* Overridden by KUnit tests. */ #ifndef fortify_panic #define fortify_panic(func, write, avail, size, retfail) … #endif #ifndef fortify_warn_once #define fortify_warn_once(x...) … #endif #define FORTIFY_READ … #define FORTIFY_WRITE … #define EACH_FORTIFY_FUNC(macro) … #define MAKE_FORTIFY_FUNC(func) … enum fortify_func { … }; void __fortify_report(const u8 reason, const size_t avail, const size_t size); void __fortify_panic(const u8 reason, const size_t avail, const size_t size) __cold __noreturn; void __read_overflow(void) __compiletime_error("detected read beyond size of object (1st parameter)"); void __read_overflow2(void) __compiletime_error("detected read beyond size of object (2nd parameter)"); void __read_overflow2_field(size_t avail, size_t wanted) __compiletime_warning("detected read beyond size of field (2nd parameter); maybe use struct_group()?"); void __write_overflow(void) __compiletime_error("detected write beyond size of object (1st parameter)"); void __write_overflow_field(size_t avail, size_t wanted) __compiletime_warning("detected write beyond size of field (1st parameter); maybe use struct_group()?"); #define __compiletime_strlen(p) … #if defined(__SANITIZE_ADDRESS__) #if !defined(CONFIG_CC_HAS_KASAN_MEMINTRINSIC_PREFIX) && !defined(CONFIG_GENERIC_ENTRY) extern void *__underlying_memset(void *p, int c, __kernel_size_t size) __RENAME(memset); extern void *__underlying_memmove(void *p, const void *q, __kernel_size_t size) __RENAME(memmove); extern void *__underlying_memcpy(void *p, const void *q, __kernel_size_t size) __RENAME(memcpy); #elif defined(CONFIG_KASAN_GENERIC) extern void *__underlying_memset(void *p, int c, __kernel_size_t size) __RENAME(__asan_memset); extern void *__underlying_memmove(void *p, const void *q, __kernel_size_t size) __RENAME(__asan_memmove); extern void *__underlying_memcpy(void *p, const void *q, __kernel_size_t size) __RENAME(__asan_memcpy); #else /* CONFIG_KASAN_SW_TAGS */ extern void *__underlying_memset(void *p, int c, __kernel_size_t size) __RENAME(__hwasan_memset); extern void *__underlying_memmove(void *p, const void *q, __kernel_size_t size) __RENAME(__hwasan_memmove); extern void *__underlying_memcpy(void *p, const void *q, __kernel_size_t size) __RENAME(__hwasan_memcpy); #endif extern void *__underlying_memchr(const void *p, int c, __kernel_size_t size) __RENAME(memchr); extern int __underlying_memcmp(const void *p, const void *q, __kernel_size_t size) __RENAME(memcmp); extern char *__underlying_strcat(char *p, const char *q) __RENAME(strcat); extern char *__underlying_strcpy(char *p, const char *q) __RENAME(strcpy); extern __kernel_size_t __underlying_strlen(const char *p) __RENAME(strlen); extern char *__underlying_strncat(char *p, const char *q, __kernel_size_t count) __RENAME(strncat); extern char *__underlying_strncpy(char *p, const char *q, __kernel_size_t size) __RENAME(strncpy); #else #if defined(__SANITIZE_MEMORY__) /* * For KMSAN builds all memcpy/memset/memmove calls should be replaced by the * corresponding __msan_XXX functions. */ #include <linux/kmsan_string.h> #define __underlying_memcpy … #define __underlying_memmove … #define __underlying_memset … #else #define __underlying_memcpy … #define __underlying_memmove … #define __underlying_memset … #endif #define __underlying_memchr … #define __underlying_memcmp … #define __underlying_strcat … #define __underlying_strcpy … #define __underlying_strlen … #define __underlying_strncat … #define __underlying_strncpy … #endif /** * unsafe_memcpy - memcpy implementation with no FORTIFY bounds checking * * @dst: Destination memory address to write to * @src: Source memory address to read from * @bytes: How many bytes to write to @dst from @src * @justification: Free-form text or comment describing why the use is needed * * This should be used for corner cases where the compiler cannot do the * right thing, or during transitions between APIs, etc. It should be used * very rarely, and includes a place for justification detailing where bounds * checking has happened, and why existing solutions cannot be employed. */ #define unsafe_memcpy(dst, src, bytes, justification) … /* * Clang's use of __builtin_*object_size() within inlines needs hinting via * __pass_*object_size(). The preference is to only ever use type 1 (member * size, rather than struct size), but there remain some stragglers using * type 0 that will be converted in the future. */ #if __has_builtin(__builtin_dynamic_object_size) #define POS … #define POS0 … #else #define POS … #define POS0 … #endif #define __compiletime_lessthan(bounds, length) … /** * strncpy - Copy a string to memory with non-guaranteed NUL padding * * @p: pointer to destination of copy * @q: pointer to NUL-terminated source string to copy * @size: bytes to write at @p * * If strlen(@q) >= @size, the copy of @q will stop after @size bytes, * and @p will NOT be NUL-terminated * * If strlen(@q) < @size, following the copy of @q, trailing NUL bytes * will be written to @p until @size total bytes have been written. * * Do not use this function. While FORTIFY_SOURCE tries to avoid * over-reads of @q, it cannot defend against writing unterminated * results to @p. Using strncpy() remains ambiguous and fragile. * Instead, please choose an alternative, so that the expectation * of @p's contents is unambiguous: * * +--------------------+--------------------+------------+ * | **p** needs to be: | padded to **size** | not padded | * +====================+====================+============+ * | NUL-terminated | strscpy_pad() | strscpy() | * +--------------------+--------------------+------------+ * | not NUL-terminated | strtomem_pad() | strtomem() | * +--------------------+--------------------+------------+ * * Note strscpy*()'s differing return values for detecting truncation, * and strtomem*()'s expectation that the destination is marked with * __nonstring when it is a character array. * */ __FORTIFY_INLINE __diagnose_as(__builtin_strncpy, 1, 2, 3) char *strncpy(char * const POS p, const char *q, __kernel_size_t size) { … } extern __kernel_size_t __real_strnlen(const char *, __kernel_size_t) __RENAME(strnlen); /** * strnlen - Return bounded count of characters in a NUL-terminated string * * @p: pointer to NUL-terminated string to count. * @maxlen: maximum number of characters to count. * * Returns number of characters in @p (NOT including the final NUL), or * @maxlen, if no NUL has been found up to there. * */ __FORTIFY_INLINE __kernel_size_t strnlen(const char * const POS p, __kernel_size_t maxlen) { … } /* * Defined after fortified strnlen to reuse it. However, it must still be * possible for strlen() to be used on compile-time strings for use in * static initializers (i.e. as a constant expression). */ /** * strlen - Return count of characters in a NUL-terminated string * * @p: pointer to NUL-terminated string to count. * * Do not use this function unless the string length is known at * compile-time. When @p is unterminated, this function may crash * or return unexpected counts that could lead to memory content * exposures. Prefer strnlen(). * * Returns number of characters in @p (NOT including the final NUL). * */ #define strlen(p) … __FORTIFY_INLINE __diagnose_as(__builtin_strlen, 1) __kernel_size_t __fortify_strlen(const char * const POS p) { … } /* Defined after fortified strnlen() to reuse it. */ extern ssize_t __real_strscpy(char *, const char *, size_t) __RENAME(sized_strscpy); __FORTIFY_INLINE ssize_t sized_strscpy(char * const POS p, const char * const POS q, size_t size) { … } /* Defined after fortified strlen() to reuse it. */ extern size_t __real_strlcat(char *p, const char *q, size_t avail) __RENAME(strlcat); /** * strlcat - Append a string to an existing string * * @p: pointer to %NUL-terminated string to append to * @q: pointer to %NUL-terminated string to append from * @avail: Maximum bytes available in @p * * Appends %NUL-terminated string @q after the %NUL-terminated * string at @p, but will not write beyond @avail bytes total, * potentially truncating the copy from @q. @p will stay * %NUL-terminated only if a %NUL already existed within * the @avail bytes of @p. If so, the resulting number of * bytes copied from @q will be at most "@avail - strlen(@p) - 1". * * Do not use this function. While FORTIFY_SOURCE tries to avoid * read and write overflows, this is only possible when the sizes * of @p and @q are known to the compiler. Prefer building the * string with formatting, via scnprintf(), seq_buf, or similar. * * Returns total bytes that _would_ have been contained by @p * regardless of truncation, similar to snprintf(). If return * value is >= @avail, the string has been truncated. * */ __FORTIFY_INLINE size_t strlcat(char * const POS p, const char * const POS q, size_t avail) { … } /* Defined after fortified strlcat() to reuse it. */ /** * strcat - Append a string to an existing string * * @p: pointer to NUL-terminated string to append to * @q: pointer to NUL-terminated source string to append from * * Do not use this function. While FORTIFY_SOURCE tries to avoid * read and write overflows, this is only possible when the * destination buffer size is known to the compiler. Prefer * building the string with formatting, via scnprintf() or similar. * At the very least, use strncat(). * * Returns @p. * */ __FORTIFY_INLINE __diagnose_as(__builtin_strcat, 1, 2) char *strcat(char * const POS p, const char *q) { … } /** * strncat - Append a string to an existing string * * @p: pointer to NUL-terminated string to append to * @q: pointer to source string to append from * @count: Maximum bytes to read from @q * * Appends at most @count bytes from @q (stopping at the first * NUL byte) after the NUL-terminated string at @p. @p will be * NUL-terminated. * * Do not use this function. While FORTIFY_SOURCE tries to avoid * read and write overflows, this is only possible when the sizes * of @p and @q are known to the compiler. Prefer building the * string with formatting, via scnprintf() or similar. * * Returns @p. * */ /* Defined after fortified strlen() and strnlen() to reuse them. */ __FORTIFY_INLINE __diagnose_as(__builtin_strncat, 1, 2, 3) char *strncat(char * const POS p, const char * const POS q, __kernel_size_t count) { … } __FORTIFY_INLINE bool fortify_memset_chk(__kernel_size_t size, const size_t p_size, const size_t p_size_field) { … } #define __fortify_memset_chk(p, c, size, p_size, p_size_field) … /* * __struct_size() vs __member_size() must be captured here to avoid * evaluating argument side-effects further into the macro layers. */ #ifndef CONFIG_KMSAN #define memset(p, c, s) … #endif /* * To make sure the compiler can enforce protection against buffer overflows, * memcpy(), memmove(), and memset() must not be used beyond individual * struct members. If you need to copy across multiple members, please use * struct_group() to create a named mirror of an anonymous struct union. * (e.g. see struct sk_buff.) Read overflow checking is currently only * done when a write overflow is also present, or when building with W=1. * * Mitigation coverage matrix * Bounds checking at: * +-------+-------+-------+-------+ * | Compile time | Run time | * memcpy() argument sizes: | write | read | write | read | * dest source length +-------+-------+-------+-------+ * memcpy(known, known, constant) | y | y | n/a | n/a | * memcpy(known, unknown, constant) | y | n | n/a | V | * memcpy(known, known, dynamic) | n | n | B | B | * memcpy(known, unknown, dynamic) | n | n | B | V | * memcpy(unknown, known, constant) | n | y | V | n/a | * memcpy(unknown, unknown, constant) | n | n | V | V | * memcpy(unknown, known, dynamic) | n | n | V | B | * memcpy(unknown, unknown, dynamic) | n | n | V | V | * +-------+-------+-------+-------+ * * y = perform deterministic compile-time bounds checking * n = cannot perform deterministic compile-time bounds checking * n/a = no run-time bounds checking needed since compile-time deterministic * B = can perform run-time bounds checking (currently unimplemented) * V = vulnerable to run-time overflow (will need refactoring to solve) * */ __FORTIFY_INLINE bool fortify_memcpy_chk(__kernel_size_t size, const size_t p_size, const size_t q_size, const size_t p_size_field, const size_t q_size_field, const u8 func) { … } #define __fortify_memcpy_chk(p, q, size, p_size, q_size, \ p_size_field, q_size_field, op) … /* * Notes about compile-time buffer size detection: * * With these types... * * struct middle { * u16 a; * u8 middle_buf[16]; * int b; * }; * struct end { * u16 a; * u8 end_buf[16]; * }; * struct flex { * int a; * u8 flex_buf[]; * }; * * void func(TYPE *ptr) { ... } * * Cases where destination size cannot be currently detected: * - the size of ptr's object (seemingly by design, gcc & clang fail): * __builtin_object_size(ptr, 1) == SIZE_MAX * - the size of flexible arrays in ptr's obj (by design, dynamic size): * __builtin_object_size(ptr->flex_buf, 1) == SIZE_MAX * - the size of ANY array at the end of ptr's obj (gcc and clang bug): * __builtin_object_size(ptr->end_buf, 1) == SIZE_MAX * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101836 * * Cases where destination size is currently detected: * - the size of non-array members within ptr's object: * __builtin_object_size(ptr->a, 1) == 2 * - the size of non-flexible-array in the middle of ptr's obj: * __builtin_object_size(ptr->middle_buf, 1) == 16 * */ /* * __struct_size() vs __member_size() must be captured here to avoid * evaluating argument side-effects further into the macro layers. */ #define memcpy(p, q, s) … #define memmove(p, q, s) … extern void *__real_memscan(void *, int, __kernel_size_t) __RENAME(memscan); __FORTIFY_INLINE void *memscan(void * const POS0 p, int c, __kernel_size_t size) { … } __FORTIFY_INLINE __diagnose_as(__builtin_memcmp, 1, 2, 3) int memcmp(const void * const POS0 p, const void * const POS0 q, __kernel_size_t size) { … } __FORTIFY_INLINE __diagnose_as(__builtin_memchr, 1, 2, 3) void *memchr(const void * const POS0 p, int c, __kernel_size_t size) { … } void *__real_memchr_inv(const void *s, int c, size_t n) __RENAME(memchr_inv); __FORTIFY_INLINE void *memchr_inv(const void * const POS0 p, int c, size_t size) { … } extern void *__real_kmemdup(const void *src, size_t len, gfp_t gfp) __RENAME(kmemdup_noprof) __realloc_size(2); __FORTIFY_INLINE void *kmemdup_noprof(const void * const POS0 p, size_t size, gfp_t gfp) { … } #define kmemdup(...) … /** * strcpy - Copy a string into another string buffer * * @p: pointer to destination of copy * @q: pointer to NUL-terminated source string to copy * * Do not use this function. While FORTIFY_SOURCE tries to avoid * overflows, this is only possible when the sizes of @q and @p are * known to the compiler. Prefer strscpy(), though note its different * return values for detecting truncation. * * Returns @p. * */ /* Defined after fortified strlen to reuse it. */ __FORTIFY_INLINE __diagnose_as(__builtin_strcpy, 1, 2) char *strcpy(char * const POS p, const char * const POS q) { … } /* Don't use these outside the FORITFY_SOURCE implementation */ #undef __underlying_memchr #undef __underlying_memcmp #undef __underlying_strcat #undef __underlying_strcpy #undef __underlying_strlen #undef __underlying_strncat #undef __underlying_strncpy #undef POS #undef POS0 #endif /* _LINUX_FORTIFY_STRING_H_ */
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