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Message-ID: <CANp29Y6MrxrKSAWx_Hqk1_mWBSWwKy39-Z_BDK09_FW3VJfF2Q@mail.gmail.com>
Date: Tue, 28 Jan 2025 19:13:02 +0100
From: Aleksandr Nogikh <nogikh@...gle.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: syzbot <syzbot+5b9196ecf74447172a9a@...kaller.appspotmail.com>,
davem@...emloft.net, johannes@...solutions.net, kuba@...nel.org,
linux-kernel@...r.kernel.org, linux-wireless@...r.kernel.org,
netdev@...r.kernel.org, pabeni@...hat.com, syzkaller-bugs@...glegroups.com,
Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [syzbot] [wireless?] possible deadlock in ieee80211_remove_interfaces
Hi Eric,
On Fri, Jan 17, 2025 at 5:14 AM 'Eric Dumazet' via syzkaller-bugs
<syzkaller-bugs@...glegroups.com> wrote:
>
> On Fri, Jan 17, 2025 at 4:58 AM syzbot
> <syzbot+5b9196ecf74447172a9a@...kaller.appspotmail.com> wrote:
> >
> > syzbot has found a reproducer for the following issue on:
> >
> > HEAD commit: 8d20dcda404d selftests: drv-net-hw: inject pp_alloc_fail e..
> > git tree: net-next
> > console output: https://syzkaller.appspot.com/x/log.txt?x=14ef5a18580000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=c30f048a4f12891
> > dashboard link: https://syzkaller.appspot.com/bug?extid=5b9196ecf74447172a9a
> > compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15d7a1f8580000
> >
> > Downloadable assets:
> > disk image: https://storage.googleapis.com/syzbot-assets/5ce07c743ced/disk-8d20dcda.raw.xz
> > vmlinux: https://storage.googleapis.com/syzbot-assets/66f2a9a35d5e/vmlinux-8d20dcda.xz
> > kernel image: https://storage.googleapis.com/syzbot-assets/4c790c086a46/bzImage-8d20dcda.xz
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+5b9196ecf74447172a9a@...kaller.appspotmail.com
> >
> > ======================================================
> > WARNING: possible circular locking dependency detected
> > 6.13.0-rc7-syzkaller-01131-g8d20dcda404d #0 Not tainted
> > ------------------------------------------------------
> > kworker/u8:6/3534 is trying to acquire lock:
> > ffffffff8fcb4a08 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_acquire_if_cleanup_net net/core/dev.c:10281 [inline]
> > ffffffff8fcb4a08 (rtnl_mutex){+.+.}-{4:4}, at: unregister_netdevice_many_notify+0xac2/0x2030 net/core/dev.c:11783
> >
> > but task is already holding lock:
> > ffff8880216b0768 (&rdev->wiphy.mtx){+.+.}-{4:4}, at: class_wiphy_constructor include/net/cfg80211.h:6034 [inline]
> > ffff8880216b0768 (&rdev->wiphy.mtx){+.+.}-{4:4}, at: ieee80211_remove_interfaces+0x129/0x700 net/mac80211/iface.c:2276
> >
> > which lock already depends on the new lock.
> >
> >
> > the existing dependency chain (in reverse order) is:
> >
> > -> #1 (&rdev->wiphy.mtx){+.+.}-{4:4}:
> > lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
> > __mutex_lock_common kernel/locking/mutex.c:585 [inline]
> > __mutex_lock+0x1ac/0xee0 kernel/locking/mutex.c:735
> > wiphy_lock include/net/cfg80211.h:6019 [inline]
> > wiphy_register+0x1a49/0x27b0 net/wireless/core.c:1006
> > ieee80211_register_hw+0x30fb/0x3e10 net/mac80211/main.c:1582
> > mac80211_hwsim_new_radio+0x2a9f/0x4a90 drivers/net/wireless/virtual/mac80211_hwsim.c:5558
> > init_mac80211_hwsim+0x87a/0xb00 drivers/net/wireless/virtual/mac80211_hwsim.c:6910
> > do_one_initcall+0x248/0x870 init/main.c:1266
> > do_initcall_level+0x157/0x210 init/main.c:1328
> > do_initcalls+0x3f/0x80 init/main.c:1344
> > kernel_init_freeable+0x435/0x5d0 init/main.c:1577
> > kernel_init+0x1d/0x2b0 init/main.c:1466
> > ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
> > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> >
> > -> #0 (rtnl_mutex){+.+.}-{4:4}:
> > check_prev_add kernel/locking/lockdep.c:3161 [inline]
> > check_prevs_add kernel/locking/lockdep.c:3280 [inline]
> > validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904
> > __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5226
> > lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
> > __mutex_lock_common kernel/locking/mutex.c:585 [inline]
> > __mutex_lock+0x1ac/0xee0 kernel/locking/mutex.c:735
> > rtnl_acquire_if_cleanup_net net/core/dev.c:10281 [inline]
> > unregister_netdevice_many_notify+0xac2/0x2030 net/core/dev.c:11783
> > unregister_netdevice_many net/core/dev.c:11866 [inline]
> > unregister_netdevice_queue+0x303/0x370 net/core/dev.c:11732
> > unregister_netdevice include/linux/netdevice.h:3320 [inline]
> > _cfg80211_unregister_wdev+0x163/0x590 net/wireless/core.c:1251
> > ieee80211_remove_interfaces+0x4ef/0x700 net/mac80211/iface.c:2301
> > ieee80211_unregister_hw+0x5d/0x2c0 net/mac80211/main.c:1676
> > mac80211_hwsim_del_radio+0x2c4/0x4c0 drivers/net/wireless/virtual/mac80211_hwsim.c:5664
> > hwsim_exit_net+0x5c1/0x670 drivers/net/wireless/virtual/mac80211_hwsim.c:6544
> > ops_exit_list net/core/net_namespace.c:172 [inline]
> > cleanup_net+0x812/0xd60 net/core/net_namespace.c:652
> > process_one_work kernel/workqueue.c:3236 [inline]
> > process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3317
> > worker_thread+0x870/0xd30 kernel/workqueue.c:3398
> > kthread+0x2f0/0x390 kernel/kthread.c:389
> > ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
> > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> >
> > other info that might help us debug this:
> >
> > Possible unsafe locking scenario:
> >
> > CPU0 CPU1
> > ---- ----
> > lock(&rdev->wiphy.mtx);
> > lock(rtnl_mutex);
> > lock(&rdev->wiphy.mtx);
> > lock(rtnl_mutex);
> >
> > *** DEADLOCK ***
> >
> > 4 locks held by kworker/u8:6/3534:
> > #0: ffff88801baf5948 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3211 [inline]
> > #0: ffff88801baf5948 ((wq_completion)netns){+.+.}-{0:0}, at: process_scheduled_works+0x93b/0x1840 kernel/workqueue.c:3317
> > #1: ffffc9000d507d00 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3212 [inline]
> > #1: ffffc9000d507d00 (net_cleanup_work){+.+.}-{0:0}, at: process_scheduled_works+0x976/0x1840 kernel/workqueue.c:3317
> > #2: ffffffff8fca8290 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0x17a/0xd60 net/core/net_namespace.c:606
> > #3: ffff8880216b0768 (&rdev->wiphy.mtx){+.+.}-{4:4}, at: class_wiphy_constructor include/net/cfg80211.h:6034 [inline]
> > #3: ffff8880216b0768 (&rdev->wiphy.mtx){+.+.}-{4:4}, at: ieee80211_remove_interfaces+0x129/0x700 net/mac80211/iface.c:2276
> >
> > stack backtrace:
> > CPU: 1 UID: 0 PID: 3534 Comm: kworker/u8:6 Not tainted 6.13.0-rc7-syzkaller-01131-g8d20dcda404d #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
> > Workqueue: netns cleanup_net
> > Call Trace:
> > <TASK>
> > __dump_stack lib/dump_stack.c:94 [inline]
> > dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
> > print_circular_bug+0x13a/0x1b0 kernel/locking/lockdep.c:2074
> > check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2206
> > check_prev_add kernel/locking/lockdep.c:3161 [inline]
> > check_prevs_add kernel/locking/lockdep.c:3280 [inline]
> > validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904
> > __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5226
> > lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
> > __mutex_lock_common kernel/locking/mutex.c:585 [inline]
> > __mutex_lock+0x1ac/0xee0 kernel/locking/mutex.c:735
> > rtnl_acquire_if_cleanup_net net/core/dev.c:10281 [inline]
> > unregister_netdevice_many_notify+0xac2/0x2030 net/core/dev.c:11783
> > unregister_netdevice_many net/core/dev.c:11866 [inline]
> > unregister_netdevice_queue+0x303/0x370 net/core/dev.c:11732
> > unregister_netdevice include/linux/netdevice.h:3320 [inline]
> > _cfg80211_unregister_wdev+0x163/0x590 net/wireless/core.c:1251
> > ieee80211_remove_interfaces+0x4ef/0x700 net/mac80211/iface.c:2301
> > ieee80211_unregister_hw+0x5d/0x2c0 net/mac80211/main.c:1676
> > mac80211_hwsim_del_radio+0x2c4/0x4c0 drivers/net/wireless/virtual/mac80211_hwsim.c:5664
> > hwsim_exit_net+0x5c1/0x670 drivers/net/wireless/virtual/mac80211_hwsim.c:6544
> > ops_exit_list net/core/net_namespace.c:172 [inline]
> > cleanup_net+0x812/0xd60 net/core/net_namespace.c:652
> > process_one_work kernel/workqueue.c:3236 [inline]
> > process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3317
> > worker_thread+0x870/0xd30 kernel/workqueue.c:3398
> > kthread+0x2f0/0x390 kernel/kthread.c:389
> > ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
> > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> > </TASK>
> > hsr_slave_0: left promiscuous mode
> > hsr_slave_1: left promiscuous mode
> > batman_adv: batadv0: Interface deactivated: batadv_slave_0
> > batman_adv: batadv0: Removing interface: batadv_slave_0
> > batman_adv: batadv0: Interface deactivated: batadv_slave_1
> > batman_adv: batadv0: Removing interface: batadv_slave_1
> > veth1_macvtap: left promiscuous mode
> > veth0_macvtap: left promiscuous mode
> > veth1_vlan: left promiscuous mode
> > veth0_vlan: left promiscuous mode
> > team0 (unregistering): Port device team_slave_1 removed
> > team0 (unregistering): Port device team_slave_0 removed
> > bridge0: port 2(bridge_slave_1) entered blocking state
> > bridge0: port 2(bridge_slave_1) entered forwarding state
> > bridge0: port 1(bridge_slave_0) entered blocking state
> > bridge0: port 1(bridge_slave_0) entered forwarding state
> > bridge0: port 2(bridge_slave_1) entered blocking state
> > bridge0: port 2(bridge_slave_1) entered forwarding state
> >
> >
> > ---
> > 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.
>
> This repro is for another bug I think, caused by my recent commits in net-next:
>
> 83419b61d187ce22aa3da5ffdda850fca3a12600 net: reduce RTNL hold
> duration in unregister_netdevice_many_notify() (part 2)
> ae646f1a0bb97401bac0044bbe2a179a1e38b408 net: reduce RTNL hold
> duration in unregister_netdevice_many_notify() (part 1)
> cfa579f6665635b72d4a075fc91eb144c2b0f74e net: no longer hold RTNL
> while calling flush_all_backlogs()
>
> cleanup_net()
> rtnl_lock();
> mutex_lock(subsystem_mutex);
>
> unregister_netdevice();
>
> rtnl_unlock(); // LOCKDEP violation
> rtnl_lock();
>
> I will work today on a fix, auditing all unregister_netdevice() and
> unregister_netdevice_many()
> and select which of them can safely opt-in for a variant which _can_
> temporarily release RTNL.
>
Could you please share what's the current situation with the fix?
The bug unfortunately keeps on stalling the fuzzing on syzbot by
causing 70+% of all daily crashes.
--
Aleksandr
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