CVE-2021-47507

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 rpc_pipefs_event() race against nfsd_net_id registration (register_pernet_subsys()) which has been fixed by commit bb7ffbf29e76 (nfsd: fix nsfd startup race triggering BUG_ON).

Restore the order of register_pernet_subsys() vs register_cld_notifier(). 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 : rpc_pipefs_event+0x54/0x120 [nfsd] lr : rpc_pipefs_event+0x48/0x120 [nfsd] Call trace: rpc_pipefs_event+0x54/0x120 [nfsd] blocking_notifier_call_chain rpc_fill_super get_tree_keyed rpc_fs_get_tree vfs_get_tree do_mount ksys_mount __arm64_sys_mount el0_svc_handler el0_svc

Affected Software

References

• https://git.kernel.org/stable/c/8bf902fee5893cfc2f04a698abab47629699ae9a
• https://git.kernel.org/stable/c/b10252c7ae9c9d7c90552f88b544a44ee773af64
• https://git.kernel.org/stable/c/c520943a00ad5015704969ad3304c956bcd49d25
• https://git.kernel.org/stable/c/f5734b1714ca355703e9ea8fb61d04beff1790b9