139 lines
3.7 KiB
C
139 lines
3.7 KiB
C
#include <linux/kernel.h>
|
|
#include <linux/export.h>
|
|
#include <linux/uaccess.h>
|
|
|
|
#include <asm/word-at-a-time.h>
|
|
|
|
/* Set bits in the first 'n' bytes when loaded from memory */
|
|
#ifdef __LITTLE_ENDIAN
|
|
# define aligned_byte_mask(n) ((1ul << 8*(n))-1)
|
|
#else
|
|
# define aligned_byte_mask(n) (~0xfful << (BITS_PER_LONG - 8 - 8*(n)))
|
|
#endif
|
|
|
|
/*
|
|
* Do a strnlen, return length of string *with* final '\0'.
|
|
* 'count' is the user-supplied count, while 'max' is the
|
|
* address space maximum.
|
|
*
|
|
* Return 0 for exceptions (which includes hitting the address
|
|
* space maximum), or 'count+1' if hitting the user-supplied
|
|
* maximum count.
|
|
*
|
|
* NOTE! We can sometimes overshoot the user-supplied maximum
|
|
* if it fits in a aligned 'long'. The caller needs to check
|
|
* the return value against "> max".
|
|
*/
|
|
static inline long do_strnlen_user(const char __user *src, unsigned long count, unsigned long max)
|
|
{
|
|
const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
|
|
long align, res = 0;
|
|
unsigned long c;
|
|
|
|
/*
|
|
* 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;
|
|
|
|
/*
|
|
* Do everything aligned. But that means that we
|
|
* need to also expand the maximum..
|
|
*/
|
|
align = (sizeof(long) - 1) & (unsigned long)src;
|
|
src -= align;
|
|
max += align;
|
|
|
|
if (unlikely(__get_user(c,(unsigned long __user *)src)))
|
|
return 0;
|
|
c |= aligned_byte_mask(align);
|
|
|
|
for (;;) {
|
|
unsigned long data;
|
|
if (has_zero(c, &data, &constants)) {
|
|
data = prep_zero_mask(c, data, &constants);
|
|
data = create_zero_mask(data);
|
|
return res + find_zero(data) + 1 - align;
|
|
}
|
|
res += sizeof(unsigned long);
|
|
/* We already handled 'unsigned long' bytes. Did we do it all ? */
|
|
if (unlikely(max <= sizeof(unsigned long)))
|
|
break;
|
|
max -= sizeof(unsigned long);
|
|
if (unlikely(__get_user(c,(unsigned long __user *)(src+res))))
|
|
return 0;
|
|
}
|
|
res -= align;
|
|
|
|
/*
|
|
* Uhhuh. We hit 'max'. But was that the user-specified maximum
|
|
* too? If so, return the marker for "too long".
|
|
*/
|
|
if (res >= count)
|
|
return count+1;
|
|
|
|
/*
|
|
* Nope: we hit the address space limit, and we still had more
|
|
* characters the caller would have wanted. That's 0.
|
|
*/
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* strnlen_user: - Get the size of a user string INCLUDING final NUL.
|
|
* @str: The string to measure.
|
|
* @count: Maximum count (including NUL character)
|
|
*
|
|
* Context: User context only. This function may sleep.
|
|
*
|
|
* Get the size of a NUL-terminated string in user space.
|
|
*
|
|
* Returns the size of the string INCLUDING the terminating NUL.
|
|
* If the string is too long, returns 'count+1'.
|
|
* On exception (or invalid count), returns 0.
|
|
*/
|
|
long strnlen_user(const char __user *str, long count)
|
|
{
|
|
unsigned long max_addr, src_addr;
|
|
|
|
if (unlikely(count <= 0))
|
|
return 0;
|
|
|
|
max_addr = user_addr_max();
|
|
src_addr = (unsigned long)str;
|
|
if (likely(src_addr < max_addr)) {
|
|
unsigned long max = max_addr - src_addr;
|
|
return do_strnlen_user(str, count, max);
|
|
}
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(strnlen_user);
|
|
|
|
/**
|
|
* strlen_user: - Get the size of a user string INCLUDING final NUL.
|
|
* @str: The string to measure.
|
|
*
|
|
* Context: User context only. This function may sleep.
|
|
*
|
|
* Get the size of a NUL-terminated string in user space.
|
|
*
|
|
* Returns the size of the string INCLUDING the terminating NUL.
|
|
* On exception, returns 0.
|
|
*
|
|
* If there is a limit on the length of a valid string, you may wish to
|
|
* consider using strnlen_user() instead.
|
|
*/
|
|
long strlen_user(const char __user *str)
|
|
{
|
|
unsigned long max_addr, src_addr;
|
|
|
|
max_addr = user_addr_max();
|
|
src_addr = (unsigned long)str;
|
|
if (likely(src_addr < max_addr)) {
|
|
unsigned long max = max_addr - src_addr;
|
|
return do_strnlen_user(str, ~0ul, max);
|
|
}
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(strlen_user);
|