sctp: fix err_chunk memory leaks in INIT handling

In the Linux kernel, the following vulnerability has been resolved: sctp: fix err_chunk memory leaks in INIT handling When sctp_verify_init() encounters unrecognized parameters, it allocates an err_chunk to report them. However, this chunk is leaked in several code paths: 1. In sctp_sf_do_5_1B_init(), if security_sctp_assoc_request() fails after sctp_verify_init() has populated err_chunk, the function returns immediately without freeing it. 2. In sctp_sf_do_unexpected_init(), the same leak occurs on the security_sctp_assoc_request() failure path. 3. In sctp_sf_do_unexpected_init(), on the success path after copying unrecognized parameters to the INIT-ACK, the function returns without freeing err_chunk, unlike sctp_sf_do_5_1B_init() which properly frees it. Fix all three leaks by adding sctp_chunk_free(err_chunk) calls before returning in the error paths and on the success path in sctp_sf_do_unexpected_init().