sparc: Add full proper error handling to strncpy_from_user().
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>
diff --git a/arch/sparc/lib/usercopy.c b/arch/sparc/lib/usercopy.c
index 14b363f..851cb75 100644
--- a/arch/sparc/lib/usercopy.c
+++ b/arch/sparc/lib/usercopy.c
@@ -1,4 +1,6 @@
#include <linux/module.h>
+#include <linux/uaccess.h>
+#include <linux/errno.h>
#include <linux/bug.h>
void copy_from_user_overflow(void)
@@ -6,3 +8,133 @@
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);