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Message-ID: <20250221123238.2944525-1-lizhi.xu@windriver.com>
Date: Fri, 21 Feb 2025 20:32:38 +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>, <lizhi.xu@...driver.com>,
<pavel@...nel.org>,
<syzbot+ace60642828c074eb913@...kaller.appspotmail.com>,
<syzkaller-bugs@...glegroups.com>
Subject: Re: [PATCH] module: replace the mutex lock acquisition method
On Fri, 21 Feb 2025 12:41:32 +0100, Rafael J. Wysocki" <rafael@...nel.org> wrote:
> > 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@...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>
> > ---
> > include/linux/moduleparam.h | 4 ++++
> > kernel/params.c | 9 ++++++++-
> > net/mac80211/rate.c | 4 +++-
> > 3 files changed, 15 insertions(+), 2 deletions(-)
> >
> > 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 -EPERM;
>
> -EAGAIN would be better I think?
Agree, -EAGAIN is more clear.
I will send a V2 patch to use -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
> > --
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