NLS: improve UTF8 -> UTF16 string conversion routine

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@suse.de>

2 files changed, 35 insertions, 11 deletions

diff --git a/fs/fat/namei_vfat.c b/fs/fat/namei_vfat.c
index a87a65663c25..c25cf151b84b 100644
--- a/fs/fat/namei_vfat.c
+++ b/fs/fat/namei_vfat.c
@@ -512,7 +512,8 @@ xlate_to_uni(const unsigned char *name, int len, unsigned char *outname,
         int charlen;
 
         if (utf8) {
-                *outlen = utf8s_to_utf16s(name, len, (wchar_t *)outname);
+                *outlen = utf8s_to_utf16s(name, len, UTF16_HOST_ENDIAN,
+                                (wchar_t *) outname, FAT_LFN_LEN + 2);
                 if (*outlen < 0)
                         return *outlen;
                 else if (*outlen > FAT_LFN_LEN)
diff --git a/fs/nls/nls_base.c b/fs/nls/nls_base.c
index 44a88a9fa2c8..0eb059ec6f28 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;