nfsd: cancel nfsd_shrinker_work using sync mode in nfs4_state_shutdown_net

Summary

In the Linux kernel, the following vulnerability has been resolved: nfsd: cancel nfsd_shrinker_work using sync mode in nfs4_state_shutdown_net In the normal case, when we excute `echo 0 > /proc/fs/nfsd/threads`, the function `nfs4_state_destroy_net` in `nfs4_state_shutdown_net` will release all resources related to the hashed `nfs4_client`. If the `nfsd_client_shrinker` is running concurrently, the `expire_client` function will first unhash this client and then destroy it. This can lead to the following warning. Additionally, numerous use-after-free errors may occur as well. nfsd_client_shrinker echo 0 > /proc/fs/nfsd/threads expire_client nfsd_shutdown_net unhash_client ... nfs4_state_shutdown_net /* won't wait shrinker exit */ /* cancel_work(&nn->nfsd_shrinker_work) • nfsd_file for this /* won't destroy unhashed client1 */ • client1 still alive nfs4_state_destroy_net */ nfsd_file_cache_shutdown /* trigger warning */ kmem_cache_destroy(nfsd_file_slab) kmem_cache_destroy(nfsd_file_mark_slab) /* release nfsd_file and mark */ __destroy_client ==================================================================== BUG nfsd_file (Not tainted): Objects remaining in nfsd_file on __kmem_cache_shutdown() -------------------------------------------------------------------- CPU: 4 UID: 0 PID: 764 Comm: sh Not tainted 6.12.0-rc3+ #1 dump_stack_lvl+0x53/0x70 slab_err+0xb0/0xf0 __kmem_cache_shutdown+0x15c/0x310 kmem_cache_destroy+0x66/0x160 nfsd_file_cache_shutdown+0xac/0x210 [nfsd] nfsd_destroy_serv+0x251/0x2a0 [nfsd] nfsd_svc+0x125/0x1e0 [nfsd] write_threads+0x16a/0x2a0 [nfsd] nfsctl_transaction_write+0x74/0xa0 [nfsd] vfs_write+0x1a5/0x6d0 ksys_write+0xc1/0x160 do_syscall_64+0x5f/0x170 entry_SYSCALL_64_after_hwframe+0x76/0x7e ==================================================================== BUG nfsd_file_mark (Tainted: G B W ): Objects remaining nfsd_file_mark on __kmem_cache_shutdown() -------------------------------------------------------------------- dump_stack_lvl+0x53/0x70 slab_err+0xb0/0xf0 __kmem_cache_shutdown+0x15c/0x310 kmem_cache_destroy+0x66/0x160 nfsd_file_cache_shutdown+0xc8/0x210 [nfsd] nfsd_destroy_serv+0x251/0x2a0 [nfsd] nfsd_svc+0x125/0x1e0 [nfsd] write_threads+0x16a/0x2a0 [nfsd] nfsctl_transaction_write+0x74/0xa0 [nfsd] vfs_write+0x1a5/0x6d0 ksys_write+0xc1/0x160 do_syscall_64+0x5f/0x170 entry_SYSCALL_64_after_hwframe+0x76/0x7e To resolve this issue, cancel `nfsd_shrinker_work` using synchronous mode in nfs4_state_shutdown_net.

Timeline

1. Nov 5, 2024, 5:10 PM UTCCVE published
2. Dec 11, 2024, 2:48 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: total

3. Oct 15, 2026, 12:57 AM UTCRecord last updated

Affected versions

• Linux Linux

  From 2bbf10861d51dae76c6da7113516d0071c782653 · fixed in f67138dd338cb564ade7d3755c8cd4f68b46d397; From 958294a3eb82026fcfff20b0287a90e9c854785e · fixed in 5ade4382de16c34d9259cb548f36ec5c4555913c; From f3ea5ec83d1a827f074b2b660749817e0bf2b23e · fixed in 36775f42e039b01d4abe8998bf66771a37d3cdcc; From 7c24fa225081f31bc6da6a355c1ba801889ab29a · fixed in f965dc0f099a54fca100acf6909abe52d0c85328; From 7c24fa225081f31bc6da6a355c1ba801889ab29a · fixed in add1df5eba163a3a6ece11cb85890e2e410baaea; From 7c24fa225081f31bc6da6a355c1ba801889ab29a · fixed in d5ff2fb2e7167e9483846e34148e60c0c016a1f6; From 5.10.220 · fixed in 5.10.233; From 5.15.154 · fixed in 5.15.176; From 6.1.81 · fixed in 6.1.123

• Linux Linux

  6.2

• KernelLinux

  fixed in 5.10.233; From 5.11.0 · fixed in 5.15.176; From 5.16.0 · fixed in 6.1.123; From 6.2.0 · fixed in 6.6.59; fixed in 6.11.6

References 6