libfdt: fix fdt_check_node_offset_ w/ VALID_INPUT

fdt_check_node_offset_() checks for a valid offset but also changes the
offset by calling fdt_next_tag(). Hence, do not skip this function if
ASSUME_VALID_INPUT is set but only omit the initial offset check in that
case.

As this function works very similar to fdt_check_prop_offset_(), do the
offset check there as well depending on ASSUME_VALID_INPUT.
Message-Id: <1913141.TlUzK5foHS@noys4>

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

libfdt/fdt.c

@@ -206,10 +206,11 @@ uint32_t fdt_next_tag(const void *fdt, int startoffset, int *nextoffset)
 
 int fdt_check_node_offset_(const void *fdt, int offset)
 {
-	if (can_assume(VALID_INPUT))
-		return offset;
-	if ((offset < 0) || (offset % FDT_TAGSIZE)
-	    || (fdt_next_tag(fdt, offset, &offset) != FDT_BEGIN_NODE))
+	if (!can_assume(VALID_INPUT)
+	    && ((offset < 0) || (offset % FDT_TAGSIZE)))
+		return -FDT_ERR_BADOFFSET;
+
+	if (fdt_next_tag(fdt, offset, &offset) != FDT_BEGIN_NODE)
 		return -FDT_ERR_BADOFFSET;
 
 	return offset;
@@ -217,8 +218,11 @@ int fdt_check_node_offset_(const void *fdt, int offset)
 
 int fdt_check_prop_offset_(const void *fdt, int offset)
 {
-	if ((offset < 0) || (offset % FDT_TAGSIZE)
-	    || (fdt_next_tag(fdt, offset, &offset) != FDT_PROP))
+	if (!can_assume(VALID_INPUT)
+	    && ((offset < 0) || (offset % FDT_TAGSIZE)))
+		return -FDT_ERR_BADOFFSET;
+
+	if (fdt_next_tag(fdt, offset, &offset) != FDT_PROP)
 		return -FDT_ERR_BADOFFSET;
 
 	return offset;