NLS: improve UTF8 -> UTF16 string conversion routine

commit 0720a06a7518c9d0c0125bd5d1f3b6264c55c3dd upstream.

The utf8s_to_utf16s conversion routine needs to be improved.  Unlike
its utf16s_to_utf8s sibling, it doesn't accept arguments specifying
the maximum length of the output buffer or the endianness of its
16-bit output.

This patch (as1501) adds the two missing arguments, and adjusts the
only two places in the kernel where the function is called.  A
follow-on patch will add a third caller that does utilize the new
capabilities.

The two conversion routines are still annoyingly inconsistent in the
way they handle invalid byte combinations.  But that's a subject for a
different patch.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
CC: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 33 insertions, 10 deletions

diff --git a/fs/nls/nls_base.c b/fs/nls/nls_base.c
index 44a88a9..0eb059e 100644
--- a/fs/nls/nls_base.c
+++ b/fs/nls/nls_base.c
@@ -114,34 +114,57 @@ int utf32_to_utf8(unicode_t u, u8 *s, int maxlen)
 }
 EXPORT_SYMBOL(utf32_to_utf8);
 
-int utf8s_to_utf16s(const u8 *s, int len, wchar_t *pwcs)
+static inline void put_utf16(wchar_t *s, unsigned c, enum utf16_endian endian)
+{
+	switch (endian) {
+	default:
+		*s = (wchar_t) c;
+		break;
+	case UTF16_LITTLE_ENDIAN:
+		*s = __cpu_to_le16(c);
+		break;
+	case UTF16_BIG_ENDIAN:
+		*s = __cpu_to_be16(c);
+		break;
+	}
+}
+
+int utf8s_to_utf16s(const u8 *s, int len, enum utf16_endian endian,
+		wchar_t *pwcs, int maxlen)
 {
 	u16 *op;
 	int size;
 	unicode_t u;
 
 	op = pwcs;
-	while (*s && len > 0) {
+	while (len > 0 && maxlen > 0 && *s) {
 		if (*s & 0x80) {
 			size = utf8_to_utf32(s, len, &u);
 			if (size < 0)
 				return -EINVAL;
+			s += size;
+			len -= size;
 
 			if (u >= PLANE_SIZE) {
+				if (maxlen < 2)
+					break;
 				u -= PLANE_SIZE;
-				*op++ = (wchar_t) (SURROGATE_PAIR |
-						((u >> 10) & SURROGATE_BITS));
-				*op++ = (wchar_t) (SURROGATE_PAIR |
+				put_utf16(op++, SURROGATE_PAIR |
+						((u >> 10) & SURROGATE_BITS),
+						endian);
+				put_utf16(op++, SURROGATE_PAIR |
 						SURROGATE_LOW |
-						(u & SURROGATE_BITS));
+						(u & SURROGATE_BITS),
+						endian);
+				maxlen -= 2;
 			} else {
-				*op++ = (wchar_t) u;
+				put_utf16(op++, u, endian);
+				maxlen--;
 			}
-			s += size;
-			len -= size;
 		} else {
-			*op++ = *s++;
+			put_utf16(op++, *s++, endian);
 			len--;
+			maxlen--;
 		}
 	}
 	return op - pwcs;