CVE-2021-47507

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> nfsd: Fix nsfd startup race (again)<br /> <br /> Commit bd5ae9288d64 ("nfsd: register pernet ops last, unregister first")<br /> has re-opened rpc_pipefs_event() race against nfsd_net_id registration<br /> (register_pernet_subsys()) which has been fixed by commit bb7ffbf29e76<br /> ("nfsd: fix nsfd startup race triggering BUG_ON").<br /> <br /> Restore the order of register_pernet_subsys() vs register_cld_notifier().<br /> Add WARN_ON() to prevent a future regression.<br /> <br /> Crash info:<br /> Unable to handle kernel NULL pointer dereference at virtual address 0000000000000012<br /> CPU: 8 PID: 345 Comm: mount Not tainted 5.4.144-... #1<br /> pc : rpc_pipefs_event+0x54/0x120 [nfsd]<br /> lr : rpc_pipefs_event+0x48/0x120 [nfsd]<br /> Call trace:<br /> rpc_pipefs_event+0x54/0x120 [nfsd]<br /> blocking_notifier_call_chain<br /> rpc_fill_super<br /> get_tree_keyed<br /> rpc_fs_get_tree<br /> vfs_get_tree<br /> do_mount<br /> ksys_mount<br /> __arm64_sys_mount<br /> el0_svc_handler<br /> el0_svc