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Message-ID: <20250222044506.351242-1-lizhi.xu@windriver.com>
Date: Sat, 22 Feb 2025 12:45:06 +0800
From: Lizhi Xu <lizhi.xu@...driver.com>
To: <rafael@...nel.org>
CC: <len.brown@...el.com>, <linux-kernel@...r.kernel.org>,
<linux-pm@...r.kernel.org>, <pavel@...nel.org>,
<syzkaller-bugs@...glegroups.com>
Subject: [PATCH V3] module: replace the mutex lock acquisition method
syzbot reported a deadlock in lock_system_sleep. [1]
The write operation to "/sys/module/hibernate/parameters/compressor"
conflicts with the registration of ieee80211 device, resulting in a deadlock
in the lock param_lock.
Replace the method of acquiring the lock system_transition_mutex with trylock,
it is arguably better to fail a write to the module param with -EBUSY than to
fail ieee80211_register_hw() IMV.
[1]
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 kernel/notifier.c:344 [inline]
blocking_notifier_call_chain_robust+0xa9/0x170 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
-> #0 (system_transition_mutex){+.+.}-{4:4}:
check_prev_add kernel/locking/lockdep.c:3163 [inline]
check_prevs_add kernel/locking/lockdep.c:3282 [inline]
validate_chain kernel/locking/lockdep.c:3906 [inline]
__lock_acquire+0x249e/0x3c40 kernel/locking/lockdep.c:5228
lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5851
__mutex_lock_common kernel/locking/mutex.c:585 [inline]
__mutex_lock+0x19b/0xb10 kernel/locking/mutex.c:730
lock_system_sleep+0x87/0xa0 kernel/power/main.c:56
hibernate_compressor_param_set+0x1c/0x210 kernel/power/hibernate.c:1452
param_attr_store+0x18f/0x300 kernel/params.c:588
module_attr_store+0x55/0x80 kernel/params.c:924
sysfs_kf_write+0x117/0x170 fs/sysfs/file.c:139
kernfs_fop_write_iter+0x33d/0x500 fs/kernfs/file.c:334
new_sync_write fs/read_write.c:586 [inline]
vfs_write+0x5ae/0x1150 fs/read_write.c:679
ksys_write+0x12b/0x250 fs/read_write.c:731
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
other info that might help us debug this:
Chain exists of:
system_transition_mutex --> rtnl_mutex --> param_lock
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(param_lock);
lock(rtnl_mutex);
lock(param_lock);
lock(system_transition_mutex);
*** DEADLOCK ***
Reported-by: syzbot+ace60642828c074eb913@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=ace60642828c074eb913
Tested-by: syzbot+ace60642828c074eb913@...kaller.appspotmail.com
Signed-off-by: Lizhi Xu <lizhi.xu@...driver.com>
---
V1 -> V2: use -EAGAIN to replace -EPERM.
V2 -> V3: replace lock_system_sleep to trylock and update comments
include/linux/suspend.h | 2 ++
kernel/power/hibernate.c | 4 +++-
kernel/power/main.c | 12 ++++++++++++
3 files changed, 17 insertions(+), 1 deletion(-)
diff --git a/include/linux/suspend.h b/include/linux/suspend.h
index da6ebca3ff77..a9ea3c0b44d7 100644
--- a/include/linux/suspend.h
+++ b/include/linux/suspend.h
@@ -468,6 +468,7 @@ extern void pm_wakep_autosleep_enabled(bool set);
extern void pm_print_active_wakeup_sources(void);
extern unsigned int lock_system_sleep(void);
+extern unsigned int trylock_system_sleep(void);
extern void unlock_system_sleep(unsigned int);
#else /* !CONFIG_PM_SLEEP */
@@ -496,6 +497,7 @@ static inline void pm_wakeup_clear(bool reset) {}
static inline void pm_system_irq_wakeup(unsigned int irq_number) {}
static inline unsigned int lock_system_sleep(void) { return 0; }
+static inline unsigned int trylock_system_sleep(void) { return 0; }
static inline void unlock_system_sleep(unsigned int flags) {}
#endif /* !CONFIG_PM_SLEEP */
diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index 10a01af63a80..eb2c424a0577 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -1449,7 +1449,9 @@ static int hibernate_compressor_param_set(const char *compressor,
unsigned int sleep_flags;
int index, ret;
- sleep_flags = lock_system_sleep();
+ sleep_flags = trylock_system_sleep();
+ if (!sleep_flags)
+ return -EBUSY;
index = sysfs_match_string(comp_alg_enabled, compressor);
if (index >= 0) {
diff --git a/kernel/power/main.c b/kernel/power/main.c
index 6254814d4817..6122c652638d 100644
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -58,6 +58,18 @@ unsigned int lock_system_sleep(void)
}
EXPORT_SYMBOL_GPL(lock_system_sleep);
+unsigned int trylock_system_sleep(void)
+{
+ unsigned int flags = current->flags;
+ current->flags |= PF_NOFREEZE;
+ if (!mutex_trylock(&system_transition_mutex)) {
+ current->flags &= ~PF_NOFREEZE;
+ return 0;
+ }
+ return flags;
+}
+EXPORT_SYMBOL_GPL(trylock_system_sleep);
+
void unlock_system_sleep(unsigned int flags)
{
if (!(flags & PF_NOFREEZE))
--
2.43.0
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