CVE-2026-22989

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

nfsd: check that server is running in unlock_filesystem

If we are trying to unlock the filesystem via an administrative interface and nfsd isnt running, it crashes the server. This happens currently because nfsd4_revoke_states() access state structures (eg., conf_id_hashtbl) that has been freed as a part of the server shutdown.

[ 59.465072] Call trace: [ 59.465308] nfsd4_revoke_states+0x1b4/0x898 [nfsd] (P) [ 59.465830] write_unlock_fs+0x258/0x440 [nfsd] [ 59.466278] nfsctl_transaction_write+0xb0/0x120 [nfsd] [ 59.466780] vfs_write+0x1f0/0x938 [ 59.467088] ksys_write+0xfc/0x1f8 [ 59.467395] __arm64_sys_write+0x74/0xb8 [ 59.467746] invoke_syscall.constprop.0+0xdc/0x1e8 [ 59.468177] do_el0_svc+0x154/0x1d8 [ 59.468489] el0_svc+0x40/0xe0 [ 59.468767] el0t_64_sync_handler+0xa0/0xe8 [ 59.469138] el0t_64_sync+0x1ac/0x1b0

Ensure this cant happen by taking the nfsd_mutex and checking that the server is still up, and then holding the mutex across the call to nfsd4_revoke_states().

Affected Software

References

• https://git.kernel.org/stable/c/d0424066fcd294977f310964bed6f2a487fa4515
• https://git.kernel.org/stable/c/d95499900fe52f3d461ed26b7a30bebea8f12914
• https://git.kernel.org/stable/c/e06c9f6c0f554148d4921c2a15bd054260a054ac