ff06dffbc8
Linus removed the end-of-address-space hackery from fs/namei.c:do_getname() so we really have to validate these edge conditions and cannot cheat any more (as x86 used to as well). Move to a common C implementation like x86 did. And if both src and dst are sufficiently aligned we'll do word at a time copies and checks as well. Signed-off-by: David S. Miller <davem@davemloft.net>
141 lines
3.3 KiB
C
141 lines
3.3 KiB
C
#include <linux/module.h>
|
|
#include <linux/uaccess.h>
|
|
#include <linux/errno.h>
|
|
#include <linux/bug.h>
|
|
|
|
void copy_from_user_overflow(void)
|
|
{
|
|
WARN(1, "Buffer overflow detected!\n");
|
|
}
|
|
EXPORT_SYMBOL(copy_from_user_overflow);
|
|
|
|
#define REPEAT_BYTE(x) ((~0ul / 0xff) * (x))
|
|
|
|
/* Return the high bit set in the first byte that is a zero */
|
|
static inline unsigned long has_zero(unsigned long a)
|
|
{
|
|
return ((a - REPEAT_BYTE(0x01)) & ~a) & REPEAT_BYTE(0x80);
|
|
}
|
|
|
|
static inline long find_zero(unsigned long c)
|
|
{
|
|
#ifdef CONFIG_64BIT
|
|
if (!(c & 0xff00000000000000UL))
|
|
return 0;
|
|
if (!(c & 0x00ff000000000000UL))
|
|
return 1;
|
|
if (!(c & 0x0000ff0000000000UL))
|
|
return 2;
|
|
if (!(c & 0x000000ff00000000UL))
|
|
return 3;
|
|
#define __OFF 4
|
|
#else
|
|
#define __OFF 0
|
|
#endif
|
|
if (!(c & 0xff000000))
|
|
return __OFF + 0;
|
|
if (!(c & 0x00ff0000))
|
|
return __OFF + 1;
|
|
if (!(c & 0x0000ff00))
|
|
return __OFF + 2;
|
|
return __OFF + 3;
|
|
#undef __OFF
|
|
}
|
|
|
|
/*
|
|
* 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)
|
|
{
|
|
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 (((long) dst | (long) src) & (sizeof(long) - 1))
|
|
goto byte_at_a_time;
|
|
|
|
while (max >= sizeof(unsigned long)) {
|
|
unsigned long c;
|
|
|
|
/* Fall back to byte-at-a-time if we get a page fault */
|
|
if (unlikely(__get_user(c,(unsigned long __user *)(src+res))))
|
|
break;
|
|
*(unsigned long *)(dst+res) = c;
|
|
if (has_zero(c))
|
|
return res + find_zero(c);
|
|
res += sizeof(unsigned long);
|
|
max -= sizeof(unsigned long);
|
|
}
|
|
|
|
byte_at_a_time:
|
|
while (max) {
|
|
char c;
|
|
|
|
if (unlikely(__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 = ~0UL;
|
|
if (likely(segment_eq(get_fs(), USER_DS)))
|
|
max_addr = STACK_TOP;
|
|
src_addr = (unsigned long)src;
|
|
if (likely(src_addr < max_addr)) {
|
|
unsigned long max = max_addr - src_addr;
|
|
return do_strncpy_from_user(dst, src, count, max);
|
|
}
|
|
return -EFAULT;
|
|
}
|
|
EXPORT_SYMBOL(strncpy_from_user);
|