[syzbot] [pm?] possible deadlock in lock_system_sleep

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 6537cfb395f3 Merge tag 'sound-6.14-rc4' of git://git.kerne..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1746afdf980000
kernel config: https://syzkaller.appspot.com/x/.config?x=61cbf5ac8a063ad4
dashboard link: https://syzkaller.appspot.com/bug?extid=ace60642828c074eb913
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13e71498580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1432cba4580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/ae2568ec9e34/disk-6537cfb3.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/19be7179f649/vmlinux-6537cfb3.xz
kernel image: https://storage.googleapis.com/syzbot-assets/bd8a168d2027/bzImage-6537cfb3.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ace606...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
6.14.0-rc3-syzkaller-00060-g6537cfb395f3 #0 Not tainted
------------------------------------------------------
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 ***

4 locks held by syz-executor895/5833:
#0: ffff8880335ec420 (sb_writers#8){.+.+}-{0:0}, at: ksys_write+0x12b/0x250 fs/read_write.c:731
#1: ffff88803398c488 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x27b/0x500 fs/kernfs/file.c:325
#2: ffff8880307af788 (kn->active#4){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x29e/0x500 fs/kernfs/file.c:326
#3: ffffffff8e07dc68 (param_lock){+.+.}-{4:4}, at: kernel_param_lock kernel/params.c:607 [inline]
#3: ffffffff8e07dc68 (param_lock){+.+.}-{4:4}, at: param_attr_store+0xe6/0x300 kernel/params.c:586

stack backtrace:
CPU: 0 UID: 0 PID: 5833 Comm: syz-executor895 Not tainted 6.14.0-rc3-syzkaller-00060-g6537cfb395f3 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
print_circular_bug+0x490/0x760 kernel/locking/lockdep.c:2076
check_noncircular+0x31a/0x400 kernel/locking/lockdep.c:2208
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
RIP: 0033:0x7f5f71a94a79
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 c1 17 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fffb2ae1de8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f5f71a94a79
RDX: 00000000000040db RSI: 0000400000005900 RDI: 0000000000000004
RBP: 00007f5f71b075f0 R08: 0000000000000006 R09: 0000000000000006
R10: 0000000000000006 R11: 0000000000000246 R12: 0000000000000001
R13: 431bde82d7b634db R14: 0000000000000001 R15: 0000000000000001
</TASK>


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

If you want to overwrite report's subsystems, reply with:
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(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

[Lizhi Xu]

#syz test

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;
+
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/include/linux/moduleparam.h b/include/linux/moduleparam.h
index bfb85fd13e1f..c7b1da7b9563 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 void 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 void kernel_param_trylock(struct module *mod)
+{
+}
static inline void kernel_param_unlock(struct module *mod)
{
}

[syzbot]

Hello,

syzbot tried to test the proposed patch but the build/boot failed:

kernel/params.c:586:13: error: invalid use of void expression
kernel/params.c:612:5: error: conflicting types for 'kernel_param_trylock'; have 'int(struct module *)'


Tested on:

commit: 319fc77f Merge tag 'bpf-fixes' of git://git.kernel.org..
git tree: upstream

kernel config: https://syzkaller.appspot.com/x/.config?x=61cbf5ac8a063ad4
dashboard link: https://syzkaller.appspot.com/bug?extid=ace60642828c074eb913
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=11503ae4580000

[Lizhi Xu]

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)

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
possible deadlock in lock_system_sleep

======================================================
WARNING: possible circular locking dependency detected

6.14.0-rc3-syzkaller-g334426094588-dirty #0 Not tainted
------------------------------------------------------
syz.0.16/6798 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_trylock kernel/params.c:614 [inline]
ffffffff8e07dc68 (param_lock){+.+.}-{4:4}, at: param_attr_store+0xe4/0x310 kernel/params.c:586

param_attr_store+0x1a7/0x310 kernel/params.c:590
module_attr_store+0x55/0x80 kernel/params.c:931

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 ***

5 locks held by syz.0.16/6798:
#0: ffff8880630bc2b8 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x267/0x390 fs/file.c:1192
#1: ffff8880358a8420 (sb_writers#8){.+.+}-{0:0}, at: ksys_write+0x12b/0x250 fs/read_write.c:731
#2: ffff88803454ac88 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x27b/0x500 fs/kernfs/file.c:325
#3: ffff88814caab2d8 (kn->active#4){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x29e/0x500 fs/kernfs/file.c:326
#4: ffffffff8e07dc68 (param_lock){+.+.}-{4:4}, at: kernel_param_trylock kernel/params.c:614 [inline]
#4: ffffffff8e07dc68 (param_lock){+.+.}-{4:4}, at: param_attr_store+0xe4/0x310 kernel/params.c:586

stack backtrace:
CPU: 1 UID: 0 PID: 6798 Comm: syz.0.16 Not tainted 6.14.0-rc3-syzkaller-g334426094588-dirty #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
print_circular_bug+0x490/0x760 kernel/locking/lockdep.c:2076
check_noncircular+0x31a/0x400 kernel/locking/lockdep.c:2208
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+0x1a7/0x310 kernel/params.c:590
module_attr_store+0x55/0x80 kernel/params.c:931

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

RIP: 0033:0x7f77a098cde9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f77a18af038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f77a0ba6080 RCX: 00007f77a098cde9

RDX: 00000000000040db RSI: 0000400000005900 RDI: 0000000000000004

RBP: 00007f77a0a0e2a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f77a0ba6080 R15: 00007fff5c12c868
</TASK>


Tested on:

commit: 33442609 Merge tag 'for-v6.14-rc' of git://git.kernel...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10943ae4580000

kernel config: https://syzkaller.appspot.com/x/.config?x=61cbf5ac8a063ad4
dashboard link: https://syzkaller.appspot.com/bug?extid=ace60642828c074eb913
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=129daba4580000

[Lizhi Xu]

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

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+ace606...@syzkaller.appspotmail.com
Tested-by: syzbot+ace606...@syzkaller.appspotmail.com

Tested on:

commit: 33442609 Merge tag 'for-v6.14-rc' of git://git.kernel...
git tree: upstream

console output: https://syzkaller.appspot.com/x/log.txt?x=126303b8580000

kernel config: https://syzkaller.appspot.com/x/.config?x=61cbf5ac8a063ad4
dashboard link: https://syzkaller.appspot.com/bug?extid=ace60642828c074eb913
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=16b0e7f8580000

Note: testing is done by a robot and is best-effort only.

[Lizhi Xu]

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]

Reported-by: syzbot+ace606...@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=ace60642828c074eb913
Tested-by: syzbot+ace606...@syzkaller.appspotmail.com
Signed-off-by: Lizhi Xu <lizh...@windriver.com>
---
include/linux/moduleparam.h | 4 ++++
kernel/params.c | 9 ++++++++-
net/mac80211/rate.c | 4 +++-
3 files changed, 15 insertions(+), 2 deletions(-)

--
2.43.0

[Rafael J. Wysocki]

-EAGAIN would be better I think?

[Lizhi Xu]

Agree, -EAGAIN is more clear.
I will send a V2 patch to use -EAGAIN.

[Lizhi Xu]

V1 -> V2: use -EAGAIN to replace -EPERM.

+ return -EAGAIN;

2.43.0

[Rafael J. Wysocki]

On Fri, Feb 21, 2025 at 1:35 PM Lizhi Xu <lizh...@windriver.com> 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.

An alternative way to avoid the deadlock would be to replace
lock_system_sleep() in hibernate_compressor_param_set() with
mutex_trylock(&system_transition_mutex) (and analogously for the
unlock operation). Why have you not done that?

It is arguably better to fail a write to the module param with -EBUSY
than to fail ieee80211_register_hw() IMV.

[Lizhi Xu]

On Fri, 21 Feb 2025 21:07:59 +0100, Rafael J. Wysocki" <raf...@kernel.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.
>
> An alternative way to avoid the deadlock would be to replace
> lock_system_sleep() in hibernate_compressor_param_set() with
> mutex_trylock(&system_transition_mutex) (and analogously for the
> unlock operation). Why have you not done that?

Yes, you are right, I have confirmed that can work fine.
I will send V2 patch for using mutex_trylock(&system_transition_mutex).

BR,
Lizhi

[Lizhi Xu]

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.

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

[Rafael J. Wysocki]

Since this is not a kthread path and it doesn't call set_freezable()
on itself anywhere, the wrapper is not needed.
mutex_trylock(&system_transition_mutex) can be called from here
directly.

[Lizhi Xu]

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.

Since this is not a kthread path and it doesn't call set_freezable()

on itself anywhere, mutex_trylock(&system_transition_mutex) can be called
from here directly.

Signed-off-by: Lizhi Xu <lizh...@windriver.com>
---
V1 -> V2: use -EAGAIN to replace -EPERM.
V2 -> V3: replace lock_system_sleep to trylock and update comments

V3 -> V4: use system_transition_mutex directly

kernel/power/hibernate.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index 10a01af63a80..b129ed1d25a8 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -1446,10 +1446,10 @@ static const char * const comp_alg_enabled[] = {

static int hibernate_compressor_param_set(const char *compressor,

const struct kernel_param *kp)
{
- unsigned int sleep_flags;

int index, ret;

- sleep_flags = lock_system_sleep();

+ if (!mutex_trylock(&system_transition_mutex))

+ return -EBUSY;

index = sysfs_match_string(comp_alg_enabled, compressor);
if (index >= 0) {

@@ -1461,7 +1461,7 @@ static int hibernate_compressor_param_set(const char *compressor,
ret = index;
}

- unlock_system_sleep(sleep_flags);
+ mutex_unlock(&system_transition_mutex);

if (ret)
pr_debug("Cannot set specified compressor %s\n",
--
2.43.0

[Rafael J. Wysocki]

Applied as 6.15 material under a new subject and with edits in the changelog.

Thanks!