xdrgen: Initialize data pointer for zero-length items

The xdrgen decoders for strings and opaque data had an
optimization that skipped calling xdr_inline_decode() when the
item length was zero. This left the data pointer uninitialized,
which could lead to unpredictable behavior when callers access
it.

Remove the zero-length check and always call xdr_inline_decode().
When passed a length of zero, xdr_inline_decode() returns the
current buffer position, which is valid and matches the behavior
of hand-coded XDR decoders throughout the kernel.

Fixes: 4b132aacb076 ("tools: Add xdrgen")
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: NeilBrown <neil@brown.name>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

diff --git a/include/linux/sunrpc/xdrgen/_builtins.h b/include/linux/sunrpc/xdrgen/_builtins.h
index 52ed9a9151c44ec659f5adcab37aff7e1f375e75..a723fb1da9c8b54e8ab79ff06d353a4ff1e6c260 100644 (file)
--- a/include/linux/sunrpc/xdrgen/_builtins.h
+++ b/include/linux/sunrpc/xdrgen/_builtins.h
@@ -248,12 +248,10 @@ xdrgen_decode_string(struct xdr_stream *xdr, string *ptr, u32 maxlen)
                return false;
        if (unlikely(maxlen && len > maxlen))
                return false;
-       if (len != 0) {
-               p = xdr_inline_decode(xdr, len);
-               if (unlikely(!p))
-                       return false;
-               ptr->data = (unsigned char *)p;
-       }
+       p = xdr_inline_decode(xdr, len);
+       if (unlikely(!p))
+               return false;
+       ptr->data = (unsigned char *)p;
        ptr->len = len;
        return true;
 }
@@ -279,12 +277,10 @@ xdrgen_decode_opaque(struct xdr_stream *xdr, opaque *ptr, u32 maxlen)
                return false;
        if (unlikely(maxlen && len > maxlen))
                return false;
-       if (len != 0) {
-               p = xdr_inline_decode(xdr, len);
-               if (unlikely(!p))
-                       return false;
-               ptr->data = (u8 *)p;
-       }
+       p = xdr_inline_decode(xdr, len);
+       if (unlikely(!p))
+               return false;
+       ptr->data = (u8 *)p;
        ptr->len = len;
        return true;
 }