CVE-2024-50142

In the Linux kernel, the following vulnerability has been resolved:

xfrm: validate new SA's prefixlen using SA family when sel.family is unset

This expands the validation introduced in commit 07bf7908950a ("xfrm: Validate address prefix lengths in the xfrm selector.")

syzbot created an SA with usersa.sel.family = AFUNSPEC usersa.sel.prefixlens = 128 usersa.family = AF_INET

Because of the AFUNSPEC selector, verifynewsainfo doesn't put limits on prefixlen{s,d}. But then copyfromuserstate sets x->sel.family to usersa.family (AFINET). Do the same conversion in verifynewsainfo before validating prefixlen_{s,d}, since that's how prefixlen is going to be used later on.