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linux-stable/include/linux/string.h
Tejun Heo 08a77676f9 string: drop __must_check from strscpy() and restore strscpy() usages in cgroup 
e7fd37ba12 ("cgroup: avoid copying strings longer than the buffers")
converted possibly unsafe strncpy() usages in cgroup to strscpy().
However, although the callsites are completely fine with truncated
copied, because strscpy() is marked __must_check, it led to the
following warnings.

  kernel/cgroup/cgroup.c: In function ‘cgroup_file_name’:
  kernel/cgroup/cgroup.c:1400:10: warning: ignoring return value of ‘strscpy’, declared with attribute warn_unused_result [-Wunused-result]
     strscpy(buf, cft->name, CGROUP_FILE_NAME_MAX);
	       ^

To avoid the warnings, 50034ed496 ("cgroup: use strlcpy() instead of
strscpy() to avoid spurious warning") switched them to strlcpy().

strlcpy() is worse than strlcpy() because it unconditionally runs
strlen() on the source string, and the only reason we switched to
strlcpy() here was because it was lacking __must_check, which doesn't
reflect any material differences between the two function.  It's just
that someone added __must_check to strscpy() and not to strlcpy().

These basic string copy operations are used in variety of ways, and
one of not-so-uncommon use cases is safely handling truncated copies,
where the caller naturally doesn't care about the return value.  The
__must_check doesn't match the actual use cases and forces users to
opt for inferior variants which lack __must_check by happenstance or
spread ugly (void) casts.

Remove __must_check from strscpy() and restore strscpy() usages in
cgroup.

Signed-off-by: Tejun Heo <tj@kernel.org>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Ma Shimiao <mashimiao.fnst@cn.fujitsu.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
2018-01-19 08:51:36 -08:00

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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_STRING_H_
#define _LINUX_STRING_H_
#include <linux/compiler.h> /* for inline */
#include <linux/types.h> /* for size_t */
#include <linux/stddef.h> /* for NULL */
#include <stdarg.h>
#include <uapi/linux/string.h>
extern char *strndup_user(const char __user *, long);
extern void *memdup_user(const void __user *, size_t);
extern void *memdup_user_nul(const void __user *, size_t);
/*
* Include machine specific inline routines
*/
#include <asm/string.h>
#ifndef __HAVE_ARCH_STRCPY
extern char * strcpy(char *,const char *);
#endif
#ifndef __HAVE_ARCH_STRNCPY
extern char * strncpy(char *,const char *, __kernel_size_t);
#endif
#ifndef __HAVE_ARCH_STRLCPY
size_t strlcpy(char *, const char *, size_t);
#endif
#ifndef __HAVE_ARCH_STRSCPY
ssize_t strscpy(char *, const char *, size_t);
#endif
#ifndef __HAVE_ARCH_STRCAT
extern char * strcat(char *, const char *);
#endif
#ifndef __HAVE_ARCH_STRNCAT
extern char * strncat(char *, const char *, __kernel_size_t);
#endif
#ifndef __HAVE_ARCH_STRLCAT
extern size_t strlcat(char *, const char *, __kernel_size_t);
#endif
#ifndef __HAVE_ARCH_STRCMP
extern int strcmp(const char *,const char *);
#endif
#ifndef __HAVE_ARCH_STRNCMP
extern int strncmp(const char *,const char *,__kernel_size_t);
#endif
#ifndef __HAVE_ARCH_STRCASECMP
extern int strcasecmp(const char *s1, const char *s2);
#endif
#ifndef __HAVE_ARCH_STRNCASECMP
extern int strncasecmp(const char *s1, const char *s2, size_t n);
#endif
#ifndef __HAVE_ARCH_STRCHR
extern char * strchr(const char *,int);
#endif
#ifndef __HAVE_ARCH_STRCHRNUL
extern char * strchrnul(const char *,int);
#endif
#ifndef __HAVE_ARCH_STRNCHR
extern char * strnchr(const char *, size_t, int);
#endif
#ifndef __HAVE_ARCH_STRRCHR
extern char * strrchr(const char *,int);
#endif
extern char * __must_check skip_spaces(const char *);
extern char *strim(char *);
static inline __must_check char *strstrip(char *str)
{
return strim(str);
}
#ifndef __HAVE_ARCH_STRSTR
extern char * strstr(const char *, const char *);
#endif
#ifndef __HAVE_ARCH_STRNSTR
extern char * strnstr(const char *, const char *, size_t);
#endif
#ifndef __HAVE_ARCH_STRLEN
extern __kernel_size_t strlen(const char *);
#endif
#ifndef __HAVE_ARCH_STRNLEN
extern __kernel_size_t strnlen(const char *,__kernel_size_t);
#endif
#ifndef __HAVE_ARCH_STRPBRK
extern char * strpbrk(const char *,const char *);
#endif
#ifndef __HAVE_ARCH_STRSEP
extern char * strsep(char **,const char *);
#endif
#ifndef __HAVE_ARCH_STRSPN
extern __kernel_size_t strspn(const char *,const char *);
#endif
#ifndef __HAVE_ARCH_STRCSPN
extern __kernel_size_t strcspn(const char *,const char *);
#endif
#ifndef __HAVE_ARCH_MEMSET
extern void * memset(void *,int,__kernel_size_t);
#endif
#ifndef __HAVE_ARCH_MEMSET16
extern void *memset16(uint16_t *, uint16_t, __kernel_size_t);
#endif
#ifndef __HAVE_ARCH_MEMSET32
extern void *memset32(uint32_t *, uint32_t, __kernel_size_t);
#endif
#ifndef __HAVE_ARCH_MEMSET64
extern void *memset64(uint64_t *, uint64_t, __kernel_size_t);
#endif
static inline void *memset_l(unsigned long *p, unsigned long v,
__kernel_size_t n)
{
if (BITS_PER_LONG == 32)
return memset32((uint32_t *)p, v, n);
else
return memset64((uint64_t *)p, v, n);
}
static inline void *memset_p(void **p, void *v, __kernel_size_t n)
{
if (BITS_PER_LONG == 32)
return memset32((uint32_t *)p, (uintptr_t)v, n);
else
return memset64((uint64_t *)p, (uintptr_t)v, n);
}
#ifndef __HAVE_ARCH_MEMCPY
extern void * memcpy(void *,const void *,__kernel_size_t);
#endif
#ifndef __HAVE_ARCH_MEMMOVE
extern void * memmove(void *,const void *,__kernel_size_t);
#endif
#ifndef __HAVE_ARCH_MEMSCAN
extern void * memscan(void *,int,__kernel_size_t);
#endif
#ifndef __HAVE_ARCH_MEMCMP
extern int memcmp(const void *,const void *,__kernel_size_t);
#endif
#ifndef __HAVE_ARCH_MEMCHR
extern void * memchr(const void *,int,__kernel_size_t);
#endif
#ifndef __HAVE_ARCH_MEMCPY_MCSAFE
static inline __must_check int memcpy_mcsafe(void *dst, const void *src,
size_t cnt)
{
memcpy(dst, src, cnt);
return 0;
}
#endif
#ifndef __HAVE_ARCH_MEMCPY_FLUSHCACHE
static inline void memcpy_flushcache(void *dst, const void *src, size_t cnt)
{
memcpy(dst, src, cnt);
}
#endif
void *memchr_inv(const void *s, int c, size_t n);
char *strreplace(char *s, char old, char new);
extern void kfree_const(const void *x);
extern char *kstrdup(const char *s, gfp_t gfp) __malloc;
extern const char *kstrdup_const(const char *s, gfp_t gfp);
extern char *kstrndup(const char *s, size_t len, gfp_t gfp);
extern void *kmemdup(const void *src, size_t len, gfp_t gfp);
extern char *kmemdup_nul(const char *s, size_t len, gfp_t gfp);
extern char **argv_split(gfp_t gfp, const char *str, int *argcp);
extern void argv_free(char **argv);
extern bool sysfs_streq(const char *s1, const char *s2);
extern int kstrtobool(const char *s, bool *res);
static inline int strtobool(const char *s, bool *res)
{
return kstrtobool(s, res);
}
int match_string(const char * const *array, size_t n, const char *string);
int __sysfs_match_string(const char * const *array, size_t n, const char *s);
/**
* sysfs_match_string - matches given string in an array
* @_a: array of strings
* @_s: string to match with
*
* Helper for __sysfs_match_string(). Calculates the size of @a automatically.
*/
#define sysfs_match_string(_a, _s) __sysfs_match_string(_a, ARRAY_SIZE(_a), _s)
#ifdef CONFIG_BINARY_PRINTF
int vbin_printf(u32 *bin_buf, size_t size, const char *fmt, va_list args);
int bstr_printf(char *buf, size_t size, const char *fmt, const u32 *bin_buf);
int bprintf(u32 *bin_buf, size_t size, const char *fmt, ...) __printf(3, 4);
#endif
extern ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos,
const void *from, size_t available);
/**
* strstarts - does @str start with @prefix?
* @str: string to examine
* @prefix: prefix to look for.
*/
static inline bool strstarts(const char *str, const char *prefix)
{
return strncmp(str, prefix, strlen(prefix)) == 0;
}
size_t memweight(const void *ptr, size_t bytes);
void memzero_explicit(void *s, size_t count);
/**
* kbasename - return the last part of a pathname.
*
* @path: path to extract the filename from.
*/
static inline const char *kbasename(const char *path)
{
const char *tail = strrchr(path, '/');
return tail ? tail + 1 : path;
}
#define __FORTIFY_INLINE extern __always_inline __attribute__((gnu_inline))
#define __RENAME(x) __asm__(#x)
void fortify_panic(const char *name) __noreturn __cold;
void __read_overflow(void) __compiletime_error("detected read beyond size of object passed as 1st parameter");
void __read_overflow2(void) __compiletime_error("detected read beyond size of object passed as 2nd parameter");
void __read_overflow3(void) __compiletime_error("detected read beyond size of object passed as 3rd parameter");
void __write_overflow(void) __compiletime_error("detected write beyond size of object passed as 1st parameter");
#if !defined(__NO_FORTIFY) && defined(__OPTIMIZE__) && defined(CONFIG_FORTIFY_SOURCE)
__FORTIFY_INLINE char *strncpy(char *p, const char *q, __kernel_size_t size)
{
size_t p_size = __builtin_object_size(p, 0);
if (__builtin_constant_p(size) && p_size < size)
__write_overflow();
if (p_size < size)
fortify_panic(__func__);
return __builtin_strncpy(p, q, size);
}
__FORTIFY_INLINE char *strcat(char *p, const char *q)
{
size_t p_size = __builtin_object_size(p, 0);
if (p_size == (size_t)-1)
return __builtin_strcat(p, q);
if (strlcat(p, q, p_size) >= p_size)
fortify_panic(__func__);
return p;
}
__FORTIFY_INLINE __kernel_size_t strlen(const char *p)
{
__kernel_size_t ret;
size_t p_size = __builtin_object_size(p, 0);
if (p_size == (size_t)-1)
return __builtin_strlen(p);
ret = strnlen(p, p_size);
if (p_size <= ret)
fortify_panic(__func__);
return ret;
}
extern __kernel_size_t __real_strnlen(const char *, __kernel_size_t) __RENAME(strnlen);
__FORTIFY_INLINE __kernel_size_t strnlen(const char *p, __kernel_size_t maxlen)
{
size_t p_size = __builtin_object_size(p, 0);
__kernel_size_t ret = __real_strnlen(p, maxlen < p_size ? maxlen : p_size);
if (p_size <= ret && maxlen != ret)
fortify_panic(__func__);
return ret;
}
/* defined after fortified strlen to reuse it */
extern size_t __real_strlcpy(char *, const char *, size_t) __RENAME(strlcpy);
__FORTIFY_INLINE size_t strlcpy(char *p, const char *q, size_t size)
{
size_t ret;
size_t p_size = __builtin_object_size(p, 0);
size_t q_size = __builtin_object_size(q, 0);
if (p_size == (size_t)-1 && q_size == (size_t)-1)
return __real_strlcpy(p, q, size);
ret = strlen(q);
if (size) {
size_t len = (ret >= size) ? size - 1 : ret;
if (__builtin_constant_p(len) && len >= p_size)
__write_overflow();
if (len >= p_size)
fortify_panic(__func__);
__builtin_memcpy(p, q, len);
p[len] = '\0';
}
return ret;
}
/* defined after fortified strlen and strnlen to reuse them */
__FORTIFY_INLINE char *strncat(char *p, const char *q, __kernel_size_t count)
{
size_t p_len, copy_len;
size_t p_size = __builtin_object_size(p, 0);
size_t q_size = __builtin_object_size(q, 0);
if (p_size == (size_t)-1 && q_size == (size_t)-1)
return __builtin_strncat(p, q, count);
p_len = strlen(p);
copy_len = strnlen(q, count);
if (p_size < p_len + copy_len + 1)
fortify_panic(__func__);
__builtin_memcpy(p + p_len, q, copy_len);
p[p_len + copy_len] = '\0';
return p;
}
__FORTIFY_INLINE void *memset(void *p, int c, __kernel_size_t size)
{
size_t p_size = __builtin_object_size(p, 0);
if (__builtin_constant_p(size) && p_size < size)
__write_overflow();
if (p_size < size)
fortify_panic(__func__);
return __builtin_memset(p, c, size);
}
__FORTIFY_INLINE void *memcpy(void *p, const void *q, __kernel_size_t size)
{
size_t p_size = __builtin_object_size(p, 0);
size_t q_size = __builtin_object_size(q, 0);
if (__builtin_constant_p(size)) {
if (p_size < size)
__write_overflow();
if (q_size < size)
__read_overflow2();
}
if (p_size < size || q_size < size)
fortify_panic(__func__);
return __builtin_memcpy(p, q, size);
}
__FORTIFY_INLINE void *memmove(void *p, const void *q, __kernel_size_t size)
{
size_t p_size = __builtin_object_size(p, 0);
size_t q_size = __builtin_object_size(q, 0);
if (__builtin_constant_p(size)) {
if (p_size < size)
__write_overflow();
if (q_size < size)
__read_overflow2();
}
if (p_size < size || q_size < size)
fortify_panic(__func__);
return __builtin_memmove(p, q, size);
}
extern void *__real_memscan(void *, int, __kernel_size_t) __RENAME(memscan);
__FORTIFY_INLINE void *memscan(void *p, int c, __kernel_size_t size)
{
size_t p_size = __builtin_object_size(p, 0);
if (__builtin_constant_p(size) && p_size < size)
__read_overflow();
if (p_size < size)
fortify_panic(__func__);
return __real_memscan(p, c, size);
}
__FORTIFY_INLINE int memcmp(const void *p, const void *q, __kernel_size_t size)
{
size_t p_size = __builtin_object_size(p, 0);
size_t q_size = __builtin_object_size(q, 0);
if (__builtin_constant_p(size)) {
if (p_size < size)
__read_overflow();
if (q_size < size)
__read_overflow2();
}
if (p_size < size || q_size < size)
fortify_panic(__func__);
return __builtin_memcmp(p, q, size);
}
__FORTIFY_INLINE void *memchr(const void *p, int c, __kernel_size_t size)
{
size_t p_size = __builtin_object_size(p, 0);
if (__builtin_constant_p(size) && p_size < size)
__read_overflow();
if (p_size < size)
fortify_panic(__func__);
return __builtin_memchr(p, c, size);
}
void *__real_memchr_inv(const void *s, int c, size_t n) __RENAME(memchr_inv);
__FORTIFY_INLINE void *memchr_inv(const void *p, int c, size_t size)
{
size_t p_size = __builtin_object_size(p, 0);
if (__builtin_constant_p(size) && p_size < size)
__read_overflow();
if (p_size < size)
fortify_panic(__func__);
return __real_memchr_inv(p, c, size);
}
extern void *__real_kmemdup(const void *src, size_t len, gfp_t gfp) __RENAME(kmemdup);
__FORTIFY_INLINE void *kmemdup(const void *p, size_t size, gfp_t gfp)
{
size_t p_size = __builtin_object_size(p, 0);
if (__builtin_constant_p(size) && p_size < size)
__read_overflow();
if (p_size < size)
fortify_panic(__func__);
return __real_kmemdup(p, size, gfp);
}
/* defined after fortified strlen and memcpy to reuse them */
__FORTIFY_INLINE char *strcpy(char *p, const char *q)
{
size_t p_size = __builtin_object_size(p, 0);
size_t q_size = __builtin_object_size(q, 0);
if (p_size == (size_t)-1 && q_size == (size_t)-1)
return __builtin_strcpy(p, q);
memcpy(p, q, strlen(q) + 1);
return p;
}
#endif
/**
* memcpy_and_pad - Copy one buffer to another with padding
* @dest: Where to copy to
* @dest_len: The destination buffer size
* @src: Where to copy from
* @count: The number of bytes to copy
* @pad: Character to use for padding if space is left in destination.
*/
static inline void memcpy_and_pad(void *dest, size_t dest_len,
const void *src, size_t count, int pad)
{
if (dest_len > count) {
memcpy(dest, src, count);
memset(dest + count, pad, dest_len - count);
} else
memcpy(dest, src, dest_len);
}
#endif /* _LINUX_STRING_H_ */
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