CVE-2025-37745 in Linux
Summary
by MITRE • 05/01/2025
In the Linux kernel, the following vulnerability has been resolved:
PM: hibernate: Avoid deadlock in hibernate_compressor_param_set()
syzbot reported a deadlock in lock_system_sleep() (see below).
The write operation to "/sys/module/hibernate/parameters/compressor" conflicts with the registration of ieee80211 device, resulting in a deadlock when attempting to acquire system_transition_mutex under param_lock.
To avoid this deadlock, change hibernate_compressor_param_set() to use mutex_trylock() for attempting to acquire system_transition_mutex and return -EBUSY when it fails.
Task flags need not be saved or adjusted before calling mutex_trylock(&system_transition_mutex) because the caller is not going to end up waiting for this mutex and if it runs concurrently with system suspend in progress, it will be frozen properly when it returns to user space.
syzbot report:
syz-executor895/5833 is trying to acquire lock: ffffffff8e0828c8 (system_transition_mutex){+.+.}-{4:4}, at: lock_system_sleep+0x87/0xa0 kernel/power/main.c:56
but task is already holding lock: ffffffff8e07dc68 (param_lock){+.+.}-{4:4}, at: kernel_param_lock kernel/params.c:607 [inline]
ffffffff8e07dc68 (param_lock){+.+.}-{4:4}, at: param_attr_store+0xe6/0x300 kernel/params.c:586
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #3 (param_lock){+.+.}-{4:4}:
__mutex_lock_common kernel/locking/mutex.c:585 [inline]
__mutex_lock+0x19b/0xb10 kernel/locking/mutex.c:730 ieee80211_rate_control_ops_get net/mac80211/rate.c:220 [inline]
rate_control_alloc net/mac80211/rate.c:266 [inline]
ieee80211_init_rate_ctrl_alg+0x18d/0x6b0 net/mac80211/rate.c:1015 ieee80211_register_hw+0x20cd/0x4060 net/mac80211/main.c:1531 mac80211_hwsim_new_radio+0x304e/0x54e0 drivers/net/wireless/virtual/mac80211_hwsim.c:5558 init_mac80211_hwsim+0x432/0x8c0 drivers/net/wireless/virtual/mac80211_hwsim.c:6910 do_one_initcall+0x128/0x700 init/main.c:1257 do_initcall_level init/main.c:1319 [inline]
do_initcalls init/main.c:1335 [inline]
do_basic_setup init/main.c:1354 [inline]
kernel_init_freeable+0x5c7/0x900 init/main.c:1568 kernel_init+0x1c/0x2b0 init/main.c:1457 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
-> #2 (rtnl_mutex){+.+.}-{4:4}:
__mutex_lock_common kernel/locking/mutex.c:585 [inline]
__mutex_lock+0x19b/0xb10 kernel/locking/mutex.c:730 wg_pm_notification drivers/net/wireguard/device.c:80 [inline]
wg_pm_notification+0x49/0x180 drivers/net/wireguard/device.c:64 notifier_call_chain+0xb7/0x410 kernel/notifier.c:85 notifier_call_chain_robust kernel/notifier.c:120 [inline]
blocking_notifier_call_chain_robust kernel/notifier.c:345 [inline]
blocking_notifier_call_chain_robust+0xc9/0x170 kernel/notifier.c:333 pm_notifier_call_chain_robust+0x27/0x60 kernel/power/main.c:102 snapshot_open+0x189/0x2b0 kernel/power/user.c:77 misc_open+0x35a/0x420 drivers/char/misc.c:179 chrdev_open+0x237/0x6a0 fs/char_dev.c:414 do_dentry_open+0x735/0x1c40 fs/open.c:956 vfs_open+0x82/0x3f0 fs/open.c:1086 do_open fs/namei.c:3830 [inline]
path_openat+0x1e88/0x2d80 fs/namei.c:3989 do_filp_open+0x20c/0x470 fs/namei.c:4016 do_sys_openat2+0x17a/0x1e0 fs/open.c:1428 do_sys_open fs/open.c:1443 [inline]
__do_sys_openat fs/open.c:1459 [inline]
__se_sys_openat fs/open.c:1454 [inline]
__x64_sys_openat+0x175/0x210 fs/open.c:1454 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #1 ((pm_chain_head).rwsem){++++}-{4:4}:
down_read+0x9a/0x330 kernel/locking/rwsem.c:1524 blocking_notifier_call_chain_robust kerne ---truncated---
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Analysis
by VulDB Data Team • 03/15/2026
The vulnerability CVE-2025-37745 resides within the Linux kernel's hibernation subsystem, specifically in the function hibernate_compressor_param_set(). This flaw manifests as a deadlock condition that occurs when attempting to set the compressor parameter through the sysfs interface at /sys/module/hibernate/parameters/compressor. The root cause stems from a circular dependency between two critical kernel locks: param_lock and system_transition_mutex. When a process attempts to modify the hibernation compressor parameter, it first acquires param_lock and then tries to acquire system_transition_mutex, which is already held by another thread involved in ieee80211 device registration. This creates a classic deadlock scenario where each thread waits indefinitely for the other's lock, effectively halting system operations.
The technical implementation of this vulnerability is deeply rooted in kernel locking mechanisms and parameter handling. The syzbot fuzzer identified the issue by tracing the execution path where a task attempting to write to the hibernation compressor parameter encounters a lock ordering problem. The param_lock is acquired during kernel parameter processing in kernel/params.c, while system_transition_mutex is required during system sleep operations in kernel/power/main.c. The dependency chain shows that the ieee80211 subsystem, which handles wireless network device registration, is already holding system_transition_mutex when it attempts to acquire param_lock, creating an unavoidable circular wait condition. This type of deadlock falls under the category of improper lock ordering, which is classified as CWE-661 in the CWE database, and represents a fundamental flaw in concurrent programming within kernel space.
The operational impact of this vulnerability extends beyond simple system hang conditions, as it can affect the entire system's ability to perform hibernation operations and potentially disrupt device registration processes. When the deadlock occurs, the system becomes unresponsive to hibernation requests and may prevent the proper initialization of wireless network devices. This vulnerability is particularly concerning in embedded systems or servers that rely on hibernation for power management or in environments where wireless device registration is frequent. From an ATT&CK perspective, this vulnerability could be exploited to perform denial-of-service attacks against systems that depend on hibernation functionality, representing a weakness in the system's resilience and availability. The vulnerability affects systems where the hibernation subsystem is actively used and where wireless network devices are being registered concurrently.
The mitigation strategy for CVE-2025-37745 involves modifying the hibernate_compressor_param_set() function to use mutex_trylock() instead of the blocking mutex_lock() when attempting to acquire system_transition_mutex. This approach prevents the deadlock by allowing the function to return immediately with -EBUSY if the mutex cannot be acquired, rather than blocking indefinitely. The fix is carefully designed to avoid unnecessary task flag manipulation since the caller does not actually need to wait for the mutex and will be properly frozen by the kernel's task management when returning to user space. This solution aligns with best practices for avoiding deadlocks in kernel code by using non-blocking lock acquisition where blocking would introduce risk of circular waits. The implementation ensures that parameter setting operations remain responsive while maintaining the integrity of system sleep operations, thus preserving the system's ability to perform hibernation while preventing the lock ordering conflict that led to the deadlock.