SUNRPC: Use unsigned string lengths in xdr_decode_string_inplace

XDR strings, opaques, and net objects should all use unsigned lengths.
To wit, RFC 4506 says:

4.2. Unsigned Integer

An XDR unsigned integer is a 32-bit datum that encodes a non-negative
integer in the range [0,4294967295].

...

4.11. String

The standard defines a string of n (numbered 0 through n-1) ASCII
bytes to be the number n encoded as an unsigned integer (as described
above), and followed by the n bytes of the string.

After this patch, xdr_decode_string_inplace now matches the other XDR
string and array helpers that take a string length argument. See:

xdr_encode_opaque_fixed, xdr_encode_opaque, xdr_encode_array

Signed-off-by: Chuck Lever <[e-mail]>
Acked-By: NeilBrown <[e-mail]>
Signed-off-by: J. Bruce Fields <[e-mail]>

include/linux/sunrpc/xdr.h

···
 __be32 *xdr_encode_opaque_fixed(__be32 *p, const void *ptr, unsigned int len);
 __be32 *xdr_encode_opaque(__be32 *p, const void *ptr, unsigned int len);
 __be32 *xdr_encode_string(__be32 *p, const char *s);
-__be32 *xdr_decode_string_inplace(__be32 *p, char **sp, int *lenp, int maxlen);
+__be32 *xdr_decode_string_inplace(__be32 *p, char **sp, unsigned int *lenp,
+			unsigned int maxlen);
 __be32 *xdr_encode_netobj(__be32 *p, const struct xdr_netobj *);
 __be32 *xdr_decode_netobj(__be32 *p, struct xdr_netobj *);
 

net/sunrpc/xdr.c

···
 EXPORT_SYMBOL(xdr_encode_string);
 
 __be32 *
-xdr_decode_string_inplace(__be32 *p, char **sp, int *lenp, int maxlen)
+xdr_decode_string_inplace(__be32 *p, char **sp,
+			  unsigned int *lenp, unsigned int maxlen)
 {
-	unsigned int	len;
+	u32 len;
 
-	if ((len = ntohl(*p++)) > maxlen)
+	len = ntohl(*p++);
+	if (len > maxlen)
 		return NULL;
 	*lenp = len;
 	*sp = (char *) p;