CVE-2023-54134
Unknown Unknown - Not Provided
Memory Leak in Linux Kernel Autofs Waitqueues Causes Resource Exhaustion

Publication date: 2025-12-24

Last updated on: 2025-12-24

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: autofs: fix memory leak of waitqueues in autofs_catatonic_mode Syzkaller reports a memory leak: BUG: memory leak unreferenced object 0xffff88810b279e00 (size 96): comm "syz-executor399", pid 3631, jiffies 4294964921 (age 23.870s) hex dump (first 32 bytes): 00 00 00 00 00 00 00 00 08 9e 27 0b 81 88 ff ff ..........'..... 08 9e 27 0b 81 88 ff ff 00 00 00 00 00 00 00 00 ..'............. backtrace: [<ffffffff814cfc90>] kmalloc_trace+0x20/0x90 mm/slab_common.c:1046 [<ffffffff81bb75ca>] kmalloc include/linux/slab.h:576 [inline] [<ffffffff81bb75ca>] autofs_wait+0x3fa/0x9a0 fs/autofs/waitq.c:378 [<ffffffff81bb88a7>] autofs_do_expire_multi+0xa7/0x3e0 fs/autofs/expire.c:593 [<ffffffff81bb8c33>] autofs_expire_multi+0x53/0x80 fs/autofs/expire.c:619 [<ffffffff81bb6972>] autofs_root_ioctl_unlocked+0x322/0x3b0 fs/autofs/root.c:897 [<ffffffff81bb6a95>] autofs_root_ioctl+0x25/0x30 fs/autofs/root.c:910 [<ffffffff81602a9c>] vfs_ioctl fs/ioctl.c:51 [inline] [<ffffffff81602a9c>] __do_sys_ioctl fs/ioctl.c:870 [inline] [<ffffffff81602a9c>] __se_sys_ioctl fs/ioctl.c:856 [inline] [<ffffffff81602a9c>] __x64_sys_ioctl+0xfc/0x140 fs/ioctl.c:856 [<ffffffff84608225>] do_syscall_x64 arch/x86/entry/common.c:50 [inline] [<ffffffff84608225>] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 [<ffffffff84800087>] entry_SYSCALL_64_after_hwframe+0x63/0xcd autofs_wait_queue structs should be freed if their wait_ctr becomes zero. Otherwise they will be lost. In this case an AUTOFS_IOC_EXPIRE_MULTI ioctl is done, then a new waitqueue struct is allocated in autofs_wait(), its initial wait_ctr equals 2. After that wait_event_killable() is interrupted (it returns -ERESTARTSYS), so that 'wq->name.name == NULL' condition may be not satisfied. Actually, this condition can be satisfied when autofs_wait_release() or autofs_catatonic_mode() is called and, what is also important, wait_ctr is decremented in those places. Upon the exit of autofs_wait(), wait_ctr is decremented to 1. Then the unmounting process begins: kill_sb calls autofs_catatonic_mode(), which should have freed the waitqueues, but it only decrements its usage counter to zero which is not a correct behaviour. edit:imk This description is of course not correct. The umount performed as a result of an expire is a umount of a mount that has been automounted, it's not the autofs mount itself. They happen independently, usually after everything mounted within the autofs file system has been expired away. If everything hasn't been expired away the automount daemon can still exit leaving mounts in place. But expires done in both cases will result in a notification that calls autofs_wait_release() with a result status. The problem case is the summary execution of of the automount daemon. In this case any waiting processes won't be woken up until either they are terminated or the mount is umounted. end edit: imk So in catatonic mode we should free waitqueues which counter becomes zero. edit: imk Initially I was concerned that the calling of autofs_wait_release() and autofs_catatonic_mode() was not mutually exclusive but that can't be the case (obviously) because the queue entry (or entries) is removed from the list when either of these two functions are called. Consequently the wait entry will be freed by only one of these functions or by the woken process in autofs_wait() depending on the order of the calls. end edit: imk
CVSS Scores
EPSS Scores
Probability:
Percentile:
Meta Information
Published
2025-12-24
Last Modified
2025-12-24
Generated
2026-05-07
AI Q&A
2025-12-25
EPSS Evaluated
2026-05-05
NVD
CVE-2023-54134
Affected Vendors & Products
Showing 2 associated CPEs
Vendor Product Version / Range
linux kernel *
linux linux_kernel *
Helpful Resources
Exploitability
CWE
CWE Icon
KEV
KEV Icon
CWE ID Description
CWE-UNKNOWN
Attack-Flow Graph
AI Powered Q&A
What immediate steps should I take to mitigate this vulnerability?

The vulnerability is fixed in the Linux kernel by ensuring that autofs waitqueues are properly freed when their usage counter reaches zero, preventing memory leaks. Immediate mitigation involves updating the Linux kernel to a version where this fix is applied.


How can this vulnerability be detected on my network or system? Can you suggest some commands?

This vulnerability involves a memory leak in the Linux kernel's autofs subsystem related to waitqueues. Detection can be done by monitoring kernel logs for memory leak BUG messages similar to those reported by Syzkaller, such as 'BUG: memory leak unreferenced object' with details about autofs waitqueues. You can check kernel logs using commands like 'dmesg | grep -i autofs' or 'journalctl -k | grep -i autofs'. Additionally, monitoring system behavior for symptoms of memory leaks or automount issues may help. However, no specific detection commands or network detection methods are provided.


Can you explain this vulnerability to me?

This vulnerability is a memory leak in the Linux kernel's autofs component. Specifically, waitqueue structures used in autofs_catatonic_mode are not properly freed when their usage counter reaches zero. This happens because during certain operations, such as an AUTOFS_IOC_EXPIRE_MULTI ioctl, waitqueues are allocated but not correctly released if interrupted. As a result, these waitqueues remain unreferenced and consume memory unnecessarily.


How can this vulnerability impact me? :

The memory leak caused by this vulnerability can lead to increased memory consumption in the system over time, potentially degrading system performance or causing resource exhaustion. This can affect the stability and reliability of systems using the autofs feature in the Linux kernel, especially if the automount daemon is frequently performing expire operations.


Ask Our AI Assistant
Need more information? Ask your question to get an AI reply (Powered by our expertise)
0/70
EPSS Chart