[Net] Fix Marshalls infinite recursion crash.

Variants like dictionaries and arrays can have cyclic references, which
caused `encode_variant` to run an infinite recursion.
Instead of keeping a stack and looking for cyclic references which would
make serialization slower, this commit adds a `MAX_RECURSION_DEPTH`
constant to Variant, and have `encode_variant` keep track of the current
recursion depth, bailing when it's too high since this likely means a
cyclic reference has been encountered.

1 files changed, 5 insertions, 0 deletions

diff --git a/core/variant/variant.h b/core/variant/variant.h
index 4dc706e853..780f9b4e70 100644
--- a/core/variant/variant.h
+++ b/core/variant/variant.h
@@ -118,6 +118,11 @@ public:
 		VARIANT_MAX
 	};
 
+	enum {
+		// Maximum recursion depth allowed when serializing variants.
+		MAX_RECURSION_DEPTH = 1024,
+	};
+
 private:
 	friend struct _VariantCall;
 	friend class VariantInternal;