In the Linux kernel, the following vulnerability has been resolved:
nfsd: Fix nsfd startup race (again)
Commit bd5ae9288d64 ("nfsd: register pernet ops last, unregister first") has re-opened rpcpipefsevent() race against nfsdnetid registration (registerpernetsubsys()) which has been fixed by commit bb7ffbf29e76 ("nfsd: fix nsfd startup race triggering BUG_ON").
Restore the order of registerpernetsubsys() vs registercldnotifier(). Add WARN_ON() to prevent a future regression.
Crash info: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000012 CPU: 8 PID: 345 Comm: mount Not tainted 5.4.144-... #1 pc : rpcpipefsevent+0x54/0x120 [nfsd] lr : rpcpipefsevent+0x48/0x120 [nfsd] Call trace: rpcpipefsevent+0x54/0x120 [nfsd] blockingnotifiercallchain rpcfillsuper gettreekeyed rpcfsgettree vfsgettree domount ksysmount _arm64sysmount el0svchandler el0svc