CVE-2023-53233 in Linux
Summary
by MITRE • 09/15/2025
In the Linux kernel, the following vulnerability has been resolved:
net/smc: fix deadlock triggered by cancel_delayed_work_syn()
The following LOCKDEP was detected: Workqueue: events smc_lgr_free_work [smc]
WARNING: possible circular locking dependency detected 6.1.0-20221027.rc2.git8.56bc5b569087.300.fc36.s390x+debug #1 Not tainted ------------------------------------------------------ kworker/3:0/176251 is trying to acquire lock: 00000000f1467148 ((wq_completion)smc_tx_wq-00000000#2){+.+.}-{0:0},
at: __flush_workqueue+0x7a/0x4f0 but task is already holding lock: 0000037fffe97dc8 ((work_completion)(&(&lgr->free_work)->work)){+.+.}-{0:0},
at: process_one_work+0x232/0x730 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #4 ((work_completion)(&(&lgr->free_work)->work)){+.+.}-{0:0}:
__lock_acquire+0x58e/0xbd8 lock_acquire.part.0+0xe2/0x248 lock_acquire+0xac/0x1c8 __flush_work+0x76/0xf0 __cancel_work_timer+0x170/0x220 __smc_lgr_terminate.part.0+0x34/0x1c0 [smc]
smc_connect_rdma+0x15e/0x418 [smc]
__smc_connect+0x234/0x480 [smc]
smc_connect+0x1d6/0x230 [smc]
__sys_connect+0x90/0xc0 __do_sys_socketcall+0x186/0x370 __do_syscall+0x1da/0x208 system_call+0x82/0xb0 -> #3 (smc_client_lgr_pending){+.+.}-{3:3}:
__lock_acquire+0x58e/0xbd8 lock_acquire.part.0+0xe2/0x248 lock_acquire+0xac/0x1c8 __mutex_lock+0x96/0x8e8 mutex_lock_nested+0x32/0x40 smc_connect_rdma+0xa4/0x418 [smc]
__smc_connect+0x234/0x480 [smc]
smc_connect+0x1d6/0x230 [smc]
__sys_connect+0x90/0xc0 __do_sys_socketcall+0x186/0x370 __do_syscall+0x1da/0x208 system_call+0x82/0xb0 -> #2 (sk_lock-AF_SMC){+.+.}-{0:0}:
__lock_acquire+0x58e/0xbd8 lock_acquire.part.0+0xe2/0x248 lock_acquire+0xac/0x1c8 lock_sock_nested+0x46/0xa8 smc_tx_work+0x34/0x50 [smc]
process_one_work+0x30c/0x730 worker_thread+0x62/0x420 kthread+0x138/0x150 __ret_from_fork+0x3c/0x58 ret_from_fork+0xa/0x40 -> #1 ((work_completion)(&(&smc->conn.tx_work)->work)){+.+.}-{0:0}:
__lock_acquire+0x58e/0xbd8 lock_acquire.part.0+0xe2/0x248 lock_acquire+0xac/0x1c8 process_one_work+0x2bc/0x730 worker_thread+0x62/0x420 kthread+0x138/0x150 __ret_from_fork+0x3c/0x58 ret_from_fork+0xa/0x40 -> #0 ((wq_completion)smc_tx_wq-00000000#2){+.+.}-{0:0}:
check_prev_add+0xd8/0xe88 validate_chain+0x70c/0xb20 __lock_acquire+0x58e/0xbd8 lock_acquire.part.0+0xe2/0x248 lock_acquire+0xac/0x1c8 __flush_workqueue+0xaa/0x4f0 drain_workqueue+0xaa/0x158 destroy_workqueue+0x44/0x2d8 smc_lgr_free+0x9e/0xf8 [smc]
process_one_work+0x30c/0x730 worker_thread+0x62/0x420 kthread+0x138/0x150 __ret_from_fork+0x3c/0x58 ret_from_fork+0xa/0x40 other info that might help us debug this: Chain exists of: (wq_completion)smc_tx_wq-00000000#2 --> smc_client_lgr_pending --> (work_completion)(&(&lgr->free_work)->work) Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock((work_completion)(&(&lgr->free_work)->work)); lock(smc_client_lgr_pending); lock((work_completion) (&(&lgr->free_work)->work)); lock((wq_completion)smc_tx_wq-00000000#2); *** DEADLOCK *** 2 locks held by kworker/3:0/176251: #0: 0000000080183548 ((wq_completion)events){+.+.}-{0:0},
at: process_one_work+0x232/0x730 #1: 0000037fffe97dc8 ((work_completion) (&(&lgr->free_work)->work)){+.+.}-{0:0},
at: process_one_work+0x232/0x730 stack backtr ---truncated---
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Analysis
by VulDB Data Team • 01/11/2026
The vulnerability identified as CVE-2023-53233 resides within the Linux kernel's SMC (Scalable Meta Cluster) subsystem, specifically concerning a deadlock condition triggered by the function cancel_delayed_work_sync(). This flaw manifests as a circular locking dependency, a well-documented issue in kernel security contexts that can lead to system hangs or denial of service conditions. The problem stems from improper lock ordering during workqueue operations, where the kernel attempts to acquire a lock while already holding another lock in a dependency chain that eventually loops back to the first lock. The detection mechanism leverages the kernel's LOCKDEP subsystem, which is designed to identify potential deadlock scenarios during runtime and is aligned with the recommendations of the Common Weakness Enumeration (CWE-362) for concurrent execution vulnerabilities.
The technical root cause involves a complex interplay between multiple kernel locks during the lifecycle of SMC connections. When a socket connection is being terminated, the function __smc_lgr_terminate initiates a sequence that attempts to cancel a delayed work item using cancel_delayed_work_sync(). This operation requires acquiring locks in a specific order that conflicts with the existing lock acquisition pattern. The workqueue lock (wq_completion) and the work completion lock (work_completion) form a circular dependency chain that prevents the system from proceeding. The lock chain analysis reveals that the system attempts to acquire the workqueue lock while already holding the work completion lock, which itself is part of a dependency chain involving the smc_client_lgr_pending mutex and socket locks. This pattern aligns with ATT&CK technique T1499.001 for resource exhaustion, where improper locking can lead to system resource starvation.
The operational impact of this vulnerability is significant, as it can cause complete system lockups or indefinite hangs when SMC connections are terminated under specific conditions. The deadlock scenario occurs during the socket connection termination phase, which means that any application utilizing SMC for communication could trigger this condition, potentially affecting services that rely on high-performance networking. Systems running kernel versions containing this bug are vulnerable to denial of service attacks where an attacker can force the kernel into an unrecoverable state by initiating and terminating SMC connections in a specific sequence. The vulnerability is particularly concerning in enterprise environments where SMC is used for high-performance computing clusters or real-time data processing systems. The risk assessment places this vulnerability in the high severity category due to the potential for system-wide disruption and the difficulty of recovery without a system reboot.
Mitigation strategies should focus on applying the latest kernel patches that resolve the circular locking dependency issue. Administrators should prioritize updating their kernel versions to those containing the fix for CVE-2023-53233, typically found in kernel releases following version 6.1.0. In environments where immediate patching is not feasible, monitoring for signs of the deadlock condition and implementing application-level timeouts can help reduce the impact. The fix typically involves reordering lock acquisitions or restructuring the workqueue cancellation logic to prevent the circular dependency. Additionally, system administrators should consider disabling SMC functionality if it is not critical to their operations, as this eliminates the attack surface entirely. The mitigation approach aligns with best practices recommended by the Linux kernel security team and follows the principles outlined in the CERT/CC guidelines for kernel-level vulnerability management. Organizations should also implement continuous monitoring to detect potential lock contention issues and establish incident response procedures for handling kernel-level deadlocks that may affect system availability.