cregit-Linux how code gets into the kernel

Release 4.7 lib/strncpy_from_user.c

Directory: lib
#include <linux/compiler.h>
#include <linux/export.h>
#include <linux/kasan-checks.h>
#include <linux/uaccess.h>
#include <linux/kernel.h>
#include <linux/errno.h>

#include <asm/byteorder.h>
#include <asm/word-at-a-time.h>


#define IS_UNALIGNED(src, dst)	0

#define IS_UNALIGNED(src, dst)	\
	(((long) dst | (long) src) & (sizeof(long) - 1))

 * Do a strncpy, return length of string without final '\0'.
 * 'count' is the user-supplied count (return 'count' if we
 * hit it), 'max' is the address space maximum (and we return
 * -EFAULT if we hit it).

static inline long do_strncpy_from_user(char *dst, const char __user *src, long count, unsigned long max) { const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS; long res = 0; /* * Truncate 'max' to the user-specified limit, so that * we only have one limit we need to check in the loop */ if (max > count) max = count; if (IS_UNALIGNED(src, dst)) goto byte_at_a_time; while (max >= sizeof(unsigned long)) { unsigned long c, data; /* Fall back to byte-at-a-time if we get a page fault */ if (unlikely(unsafe_get_user(c,(unsigned long __user *)(src+res)))) break; *(unsigned long *)(dst+res) = c; if (has_zero(c, &data, &constants)) { data = prep_zero_mask(c, data, &constants); data = create_zero_mask(data); return res + find_zero(data); } res += sizeof(unsigned long); max -= sizeof(unsigned long); } byte_at_a_time: while (max) { char c; if (unlikely(unsafe_get_user(c,src+res))) return -EFAULT; dst[res] = c; if (!c) return res; res++; max--; } /* * Uhhuh. We hit 'max'. But was that the user-specified maximum * too? If so, that's ok - we got as much as the user asked for. */ if (res >= count) return res; /* * Nope: we hit the address space limit, and we still had more * characters the caller would have wanted. That's an EFAULT. */ return -EFAULT; }


david s. millerdavid s. miller20786.97%133.33%
linus torvaldslinus torvalds3113.03%266.67%

/** * strncpy_from_user: - Copy a NUL terminated string from userspace. * @dst: Destination address, in kernel space. This buffer must be at * least @count bytes long. * @src: Source address, in user space. * @count: Maximum number of bytes to copy, including the trailing NUL. * * Copies a NUL-terminated string from userspace to kernel space. * * On success, returns the length of the string (not including the trailing * NUL). * * If access to userspace fails, returns -EFAULT (some data may have been * copied). * * If @count is smaller than the length of the string, copies @count bytes * and returns @count. */
long strncpy_from_user(char *dst, const char __user *src, long count) { unsigned long max_addr, src_addr; if (unlikely(count <= 0)) return 0; max_addr = user_addr_max(); src_addr = (unsigned long)src; if (likely(src_addr < max_addr)) { unsigned long max = max_addr - src_addr; long retval; kasan_check_write(dst, count); user_access_begin(); retval = do_strncpy_from_user(dst, src, count, max); user_access_end(); return retval; } return -EFAULT; }


david s. millerdavid s. miller8379.81%133.33%
linus torvaldslinus torvalds1413.46%133.33%
andrey ryabininandrey ryabinin76.73%133.33%


Overall Contributors

david s. millerdavid s. miller33784.46%120.00%
linus torvaldslinus torvalds4812.03%240.00%
andrey ryabininandrey ryabinin102.51%120.00%
rasmus villemoesrasmus villemoes41.00%120.00%
Directory: lib
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