CVE-2023-53629 in Linux
Summary
by MITRE • 10/07/2025
In the Linux kernel, the following vulnerability has been resolved:
fs: dlm: fix use after free in midcomms commit
While working on processing dlm message in softirq context I experienced the following KASAN use-after-free warning:
[ 151.760477] ==================================================================
[ 151.761803] BUG: KASAN: use-after-free in dlm_midcomms_commit_mhandle+0x19d/0x4b0
[ 151.763414] Read of size 4 at addr ffff88811a980c60 by task lock_torture/1347
[ 151.765284] CPU: 7 PID: 1347 Comm: lock_torture Not tainted 6.1.0-rc4+ #2828
[ 151.766778] Hardware name: Red Hat KVM/RHEL-AV, BIOS 1.16.0-3.module+el8.7.0+16134+e5908aa2 04/01/2014
[ 151.768726] Call Trace:
[ 151.769277] <TASK>
[ 151.769748] dump_stack_lvl+0x5b/0x86
[ 151.770556] print_report+0x180/0x4c8
[ 151.771378] ? kasan_complete_mode_report_info+0x7c/0x1e0
[ 151.772241] ? dlm_midcomms_commit_mhandle+0x19d/0x4b0
[ 151.773069] kasan_report+0x93/0x1a0
[ 151.773668] ? dlm_midcomms_commit_mhandle+0x19d/0x4b0
[ 151.774514] __asan_load4+0x7e/0xa0
[ 151.775089] dlm_midcomms_commit_mhandle+0x19d/0x4b0
[ 151.775890] ? create_message.isra.29.constprop.64+0x57/0xc0
[ 151.776770] send_common+0x19f/0x1b0
[ 151.777342] ? remove_from_waiters+0x60/0x60
[ 151.778017] ? lock_downgrade+0x410/0x410
[ 151.778648] ? __this_cpu_preempt_check+0x13/0x20
[ 151.779421] ? rcu_lockdep_current_cpu_online+0x88/0xc0
[ 151.780292] _convert_lock+0x46/0x150
[ 151.780893] convert_lock+0x7b/0xc0
[ 151.781459] dlm_lock+0x3ac/0x580
[ 151.781993] ? 0xffffffffc0540000
[ 151.782522] ? torture_stop+0x120/0x120 [dlm_locktorture]
[ 151.783379] ? dlm_scan_rsbs+0xa70/0xa70
[ 151.784003] ? preempt_count_sub+0xd6/0x130
[ 151.784661] ? is_module_address+0x47/0x70
[ 151.785309] ? torture_stop+0x120/0x120 [dlm_locktorture]
[ 151.786166] ? 0xffffffffc0540000
[ 151.786693] ? lockdep_init_map_type+0xc3/0x360
[ 151.787414] ? 0xffffffffc0540000
[ 151.787947] torture_dlm_lock_sync.isra.3+0xe9/0x150 [dlm_locktorture]
[ 151.789004] ? torture_stop+0x120/0x120 [dlm_locktorture]
[ 151.789858] ? 0xffffffffc0540000
[ 151.790392] ? lock_torture_cleanup+0x20/0x20 [dlm_locktorture]
[ 151.791347] ? delay_tsc+0x94/0xc0
[ 151.791898] torture_ex_iter+0xc3/0xea [dlm_locktorture]
[ 151.792735] ? torture_start+0x30/0x30 [dlm_locktorture]
[ 151.793606] lock_torture+0x177/0x270 [dlm_locktorture]
[ 151.794448] ? torture_dlm_lock_sync.isra.3+0x150/0x150 [dlm_locktorture]
[ 151.795539] ? lock_torture_stats+0x80/0x80 [dlm_locktorture]
[ 151.796476] ? do_raw_spin_lock+0x11e/0x1e0
[ 151.797152] ? mark_held_locks+0x34/0xb0
[ 151.797784] ? _raw_spin_unlock_irqrestore+0x30/0x70
[ 151.798581] ? __kthread_parkme+0x79/0x110
[ 151.799246] ? trace_preempt_on+0x2a/0xf0
[ 151.799902] ? __kthread_parkme+0x79/0x110
[ 151.800579] ? preempt_count_sub+0xd6/0x130
[ 151.801271] ? __kasan_check_read+0x11/0x20
[ 151.801963] ? __kthread_parkme+0xec/0x110
[ 151.802630] ? lock_torture_stats+0x80/0x80 [dlm_locktorture]
[ 151.803569] kthread+0x192/0x1d0
[ 151.804104] ? kthread_complete_and_exit+0x30/0x30
[ 151.804881] ret_from_fork+0x1f/0x30
[ 151.805480] </TASK>
[ 151.806111] Allocated by task 1347:
[ 151.806681] kasan_save_stack+0x26/0x50
[ 151.807308] kasan_set_track+0x25/0x30
[ 151.807920] kasan_save_alloc_info+0x1e/0x30
[ 151.808609] __kasan_slab_alloc+0x63/0x80
[ 151.809263] kmem_cache_alloc+0x1ad/0x830
[ 151.809916] dlm_allocate_mhandle+0x17/0x20
[ 151.810590] dlm_midcomms_get_mhandle+0x96/0x260
[ 151.811344] _create_message+0x95/0x180
[ 151.811994] create_message.isra.29.constprop.64+0x57/0xc0
[ 151.812880] send_common+0x129/0x1b0
[ 151.813467] _convert_lock+0x46/0x150
[ 151.814074] convert_lock+0x7b/0xc0
[ 151.814648] dlm_lock+0x3ac/0x580
[ 151.815199] torture_dlm_lock_sync.isra.3+0xe9/0x150 [dlm_locktorture]
[ 151.816258] torture_ex_iter+0xc3/0xea [dlm_locktorture]
[ 151.817129] lock_t
---truncated---
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Analysis
by VulDB Data Team • 04/20/2026
The vulnerability identified as CVE-2023-53629 resides within the Linux kernel's distributed lock manager subsystem, specifically in the dlm module's midcomms layer. This issue manifests as a use-after-free condition during the processing of distributed lock manager messages within a softirq context, which is a critical concurrency scenario in kernel space. The flaw occurs when the dlm_midcomms_commit_mhandle function attempts to access memory that has already been freed, leading to potential system instability, data corruption, or exploitation by malicious actors. The kernel address sanitizer (KASAN) detected this issue during a lock torture test scenario, where concurrent locking operations were being performed under stress conditions, highlighting the vulnerability's exposure during high-concurrency workloads. The call trace demonstrates that the problematic access originates from a dlm_lock operation, which then flows through several intermediate functions including send_common, _convert_lock, and ultimately to the dlm_midcomms_commit_mhandle function, indicating a complex interaction between the locking mechanism and message handling components.
The technical root cause of this vulnerability stems from improper memory management within the dlm subsystem's communication layer. When handling distributed lock requests, the system allocates memory for message handles using dlm_allocate_mhandle and dlm_midcomms_get_mhandle functions, but fails to ensure that this memory remains valid during the commit phase of message processing. The use-after-free condition arises because the memory allocated for the message handle is freed before the commit operation completes, yet the commit function still attempts to read from this freed memory location. This memory management error violates fundamental safety principles and creates a potential attack surface where an attacker could potentially exploit the dangling pointer to execute arbitrary code or cause a denial of service. The vulnerability is classified under CWE-416, which describes the use of freed memory condition, and aligns with ATT&CK technique T1068, which involves exploiting local privilege escalation through kernel vulnerabilities. The issue is particularly concerning because it occurs in a softirq context, which means it can be triggered by normal system operations and may not require special privileges to exploit.
The operational impact of this vulnerability extends beyond simple system crashes, as it can lead to complete system instability and potential privilege escalation. When the kernel encounters this use-after-free condition, it may trigger a kernel panic or allow for memory corruption that could be leveraged by attackers to gain elevated privileges. The vulnerability is especially dangerous in environments where distributed locking is heavily used, such as high-availability clusters, storage systems, or database applications that rely on the dlm for coordination. The fact that this was detected during a torture test indicates that the vulnerability can be reliably triggered under stress conditions, making it a significant risk for production systems. Systems running affected kernel versions are vulnerable to potential exploitation, particularly in scenarios involving concurrent locking operations or distributed workloads. The memory access pattern suggests that an attacker could potentially control the contents of the freed memory or manipulate the system to force specific memory layouts that could enable more sophisticated exploitation techniques.
Mitigation strategies for CVE-2023-53629 primarily involve applying the kernel patch that resolves the use-after-free condition in the dlm midcomms layer. The fix ensures that message handle memory is properly managed and not freed until all references to it have been completed. System administrators should prioritize updating to kernel versions that contain the patched dlm module, particularly those released after the vulnerability disclosure. Monitoring for KASAN warnings or kernel oops messages related to dlm operations should be implemented as part of security operations procedures. In environments where immediate kernel updates are not feasible, administrators can consider reducing the concurrency load on distributed locking operations or implementing additional monitoring to detect potential exploitation attempts. The vulnerability highlights the importance of proper memory management in kernel space and the critical need for thorough testing of concurrent operations in distributed systems. Organizations should also review their distributed locking usage patterns and consider implementing additional security controls around kernel memory management to prevent similar issues from occurring in other subsystems. Regular kernel updates and security audits remain essential practices for maintaining system integrity and protecting against such low-level vulnerabilities.