CVE-2024-50121 Information

Nov 06, 2024 cve

Description

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.

Reference

https://git.kernel.org/stable/c/f965dc0f099a54fca100acf6909abe52d0c85328 https://git.kernel.org/stable/c/add1df5eba163a3a6ece11cb85890e2e410baaea https://git.kernel.org/stable/c/d5ff2fb2e7167e9483846e34148e60c0c016a1f6

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