Keep the object alive across jsonSerialize() in json_encode()#22469
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iliaal wants to merge 1 commit into
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Keep the object alive across jsonSerialize() in json_encode()#22469iliaal wants to merge 1 commit into
iliaal wants to merge 1 commit into
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php_json_encode_serializable_object() holds a raw pointer to the object across the jsonSerialize() call, then reads its recursion guard and compares the returned value's identity against it. A user error handler triggered from jsonSerialize() can drop the last reference to the object, for example by nulling a reference that aliases the encoded array slot, freeing it before those reads and causing a use-after-free. Hold a reference on the object across the call. The array path already guards against this with a ZVAL_COPY; the JsonSerializable object path did not. Same use-after-free class as phpGH-21024 in var_dump().
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json_encode() can use-after-free a JsonSerializable object when its jsonSerialize() triggers a user error handler that frees the object, for example by nulling a reference that aliases the encoded array slot. php_json_encode_serializable_object() holds a raw pointer to the object across the call and then reads its recursion guard and compares identity against the return value.
Fix: hold a reference on the object across the call. The array path already guards against this with a ZVAL_COPY ("Avoid modifications (and potential freeing) of the array... when a jsonSerialize() method is invoked"); the JsonSerializable object path did not.