CVE-2026-89696 nfsd: block non-SAVEFH ops after FOREIGN PUTFH to prevent NULL deref

In the Linux kernel, the following vulnerability has been resolved: nfsd: block non-SAVEFH ops after FOREIGN PUTFH to prevent NULL deref When CONFIGNFSDV42INTERSSC is enabled, nfsd4putfh can return success with fhdentry and fhexport both NULL if fhverify returns nfserrstale and putfh-noverify is...