kernel: sctp: fix a potential overflow in sctp_ifwdtsn_skip

In the Linux kernel, the following vulnerability has been resolved: sctp: fix a potential overflow in sctpifwdtsnskip Currently, when traversing ifwdtsn skips with sctpwalkifwdtsn, it only checks the pos against the end of the chunk. However, the data left for the last pos may be sizeofstruct...