CVE-2026-52993 tipc: fix double-free in tipc_buf_append()

In the Linux kernel, the following vulnerability has been resolved: tipc: fix double-free in tipcbufappend tipcmsgvalidate can potentially reallocate the skb it is validating, freeing the old one. In tipcbufappend, it was being called with a pointer to a local variable which was a copy of the...