3.7 KiB
CVE-2024-50121
Description
In the Linux kernel, the following vulnerability has been resolved:nfsd: cancel nfsd_shrinker_work using sync mode in nfs4_state_shutdown_netIn the normal case, when we excute echo 0 > /proc/fs/nfsd/threads, thefunction nfs4_state_destroy_net in nfs4_state_shutdown_net willrelease all resources related to the hashed nfs4_client. If thenfsd_client_shrinker is running concurrently, the expire_clientfunction will first unhash this client and then destroy it. This canlead to the following warning. Additionally, numerous use-after-freeerrors may occur as well.nfsd_client_shrinker echo 0 > /proc/fs/nfsd/threadsexpire_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 remainingnfsd_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+0x76/0x7eTo resolve this issue, cancel nfsd_shrinker_work using synchronousmode in nfs4_state_shutdown_net.
POC
Reference
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