[linux-2.6-block.git] / lib / strncpy_from_user.c

#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>

#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
#define IS_UNALIGNED(src, dst)	0
#else
#define IS_UNALIGNED(src, dst)	\
	(((long) dst | (long) src) & (sizeof(long) - 1))
#endif

/*
 * 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;
}

/**
 * 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;
}
EXPORT_SYMBOL(strncpy_from_user);
Commit	Line	Data
bf3c2d6d RV	1	#include <linux/compiler.h>
bf3c2d6d RV	2	#include <linux/export.h>
1771c6e1	3	#include <linux/kasan-checks.h>
2922585b DM	4	#include <linux/uaccess.h>
	5	#include <linux/kernel.h>
	6	#include <linux/errno.h>
	7
	8	#include <asm/byteorder.h>
36126f8f	9	#include <asm/word-at-a-time.h>
2922585b DM	10
	11	#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
	12	#define IS_UNALIGNED(src, dst) 0
	13	#else
	14	#define IS_UNALIGNED(src, dst) \
	15	(((long) dst \| (long) src) & (sizeof(long) - 1))
	16	#endif
	17
	18	/*
	19	* Do a strncpy, return length of string without final '\0'.
	20	* 'count' is the user-supplied count (return 'count' if we
	21	* hit it), 'max' is the address space maximum (and we return
	22	* -EFAULT if we hit it).
	23	*/
	24	static inline long do_strncpy_from_user(char dst, const char __user src, long count, unsigned long max)
	25	{
36126f8f	26	const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
2922585b DM	27	long res = 0;
	28
	29	/*
	30	* Truncate 'max' to the user-specified limit, so that
	31	* we only have one limit we need to check in the loop
	32	*/
	33	if (max > count)
	34	max = count;
	35
	36	if (IS_UNALIGNED(src, dst))
	37	goto byte_at_a_time;
	38
	39	while (max >= sizeof(unsigned long)) {
36126f8f	40	unsigned long c, data;
2922585b DM	41
2922585b DM	42	/* Fall back to byte-at-a-time if we get a page fault */
9fd4470f	43	if (unlikely(unsafe_get_user(c,(unsigned long __user *)(src+res))))
2922585b	44	break;
2922585b	45	(unsigned long )(dst+res) = c;
36126f8f LT	46	if (has_zero(c, &data, &constants)) {
	47	data = prep_zero_mask(c, data, &constants);
	48	data = create_zero_mask(data);
	49	return res + find_zero(data);
2922585b DM	50	}
	51	res += sizeof(unsigned long);
	52	max -= sizeof(unsigned long);
	53	}
	54
	55	byte_at_a_time:
	56	while (max) {
	57	char c;
	58
9fd4470f	59	if (unlikely(unsafe_get_user(c,src+res)))
2922585b DM	60	return -EFAULT;
	61	dst[res] = c;
	62	if (!c)
	63	return res;
	64	res++;
	65	max--;
	66	}
	67
	68	/*
	69	* Uhhuh. We hit 'max'. But was that the user-specified maximum
	70	* too? If so, that's ok - we got as much as the user asked for.
	71	*/
	72	if (res >= count)
	73	return res;
	74
	75	/*
	76	* Nope: we hit the address space limit, and we still had more
	77	* characters the caller would have wanted. That's an EFAULT.
	78	*/
	79	return -EFAULT;
	80	}
	81
	82	/**
	83	* strncpy_from_user: - Copy a NUL terminated string from userspace.
	84	* @dst: Destination address, in kernel space. This buffer must be at
	85	* least @count bytes long.
	86	* @src: Source address, in user space.
	87	* @count: Maximum number of bytes to copy, including the trailing NUL.
	88	*
	89	* Copies a NUL-terminated string from userspace to kernel space.
	90	*
	91	* On success, returns the length of the string (not including the trailing
	92	* NUL).
	93	*
	94	* If access to userspace fails, returns -EFAULT (some data may have been
	95	* copied).
	96	*
	97	* If @count is smaller than the length of the string, copies @count bytes
	98	* and returns @count.
	99	*/
	100	long strncpy_from_user(char dst, const char __user src, long count)
	101	{
	102	unsigned long max_addr, src_addr;
	103
	104	if (unlikely(count <= 0))
	105	return 0;
	106
	107	max_addr = user_addr_max();
	108	src_addr = (unsigned long)src;
	109	if (likely(src_addr < max_addr)) {
	110	unsigned long max = max_addr - src_addr;
9fd4470f LT	111	long retval;
9fd4470f LT	112
1771c6e1	113	kasan_check_write(dst, count);
9fd4470f LT	114	user_access_begin();
	115	retval = do_strncpy_from_user(dst, src, count, max);
	116	user_access_end();
	117	return retval;
2922585b DM	118	}
	119	return -EFAULT;
	120	}
	121	EXPORT_SYMBOL(strncpy_from_user);