diff mbox series

[V2] module: replace the mutex lock acquisition method

Message ID 20250221123536.2946377-1-lizhi.xu@windriver.com
State Superseded
Headers show
Series [V2] module: replace the mutex lock acquisition method | expand

Commit Message

Lizhi Xu Feb. 21, 2025, 12:35 p.m. UTC 
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.

Since the conflict cannot be avoided, the way to obtain param_lock is changed
to trylock to avoid deadlock.

[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@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=ace60642828c074eb913
Tested-by: syzbot+ace60642828c074eb913@syzkaller.appspotmail.com
Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com>
---
V1 -> V2: use -EAGAIN to replace -EPERM.

 include/linux/moduleparam.h | 4 ++++
 kernel/params.c             | 9 ++++++++-
 net/mac80211/rate.c         | 4 +++-
 3 files changed, 15 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/include/linux/moduleparam.h b/include/linux/moduleparam.h
index bfb85fd13e1f..cbcbfd8db721 100644
--- a/include/linux/moduleparam.h
+++ b/include/linux/moduleparam.h
@@ -306,11 +306,15 @@  struct kparam_array
 
 #ifdef CONFIG_SYSFS
 extern void kernel_param_lock(struct module *mod);
+extern int kernel_param_trylock(struct module *mod);
 extern void kernel_param_unlock(struct module *mod);
 #else
 static inline void kernel_param_lock(struct module *mod)
 {
 }
+static inline int kernel_param_trylock(struct module *mod)
+{
+}
 static inline void kernel_param_unlock(struct module *mod)
 {
 }
diff --git a/kernel/params.c b/kernel/params.c
index 0074d29c9b80..d19881fbb2ec 100644
--- a/kernel/params.c
+++ b/kernel/params.c
@@ -583,7 +583,9 @@  static ssize_t param_attr_store(const struct module_attribute *mattr,
 	if (!attribute->param->ops->set)
 		return -EPERM;
 
-	kernel_param_lock(mk->mod);
+	if (!kernel_param_trylock(mk->mod))
+		return -EAGAIN;
+
 	if (param_check_unsafe(attribute->param))
 		err = attribute->param->ops->set(buf, attribute->param);
 	else
@@ -607,6 +609,11 @@  void kernel_param_lock(struct module *mod)
 	mutex_lock(KPARAM_MUTEX(mod));
 }
 
+int kernel_param_trylock(struct module *mod)
+{
+	return mutex_trylock(KPARAM_MUTEX(mod));
+}
+
 void kernel_param_unlock(struct module *mod)
 {
 	mutex_unlock(KPARAM_MUTEX(mod));
diff --git a/net/mac80211/rate.c b/net/mac80211/rate.c
index 0d056db9f81e..aecf7ff51cd9 100644
--- a/net/mac80211/rate.c
+++ b/net/mac80211/rate.c
@@ -217,7 +217,9 @@  ieee80211_rate_control_ops_get(const char *name)
 	const struct rate_control_ops *ops;
 	const char *alg_name;
 
-	kernel_param_lock(THIS_MODULE);
+	if (!kernel_param_trylock(THIS_MODULE))
+		return NULL;
+
 	if (!name)
 		alg_name = ieee80211_default_rc_algo;
 	else