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Message-ID: <47e4a5e1-bacd-4607-bc36-ee8f13a506f1@davidwei.uk> Date: Wed, 24 Jul 2024 14:39:11 -0700 From: David Wei <dw@...idwei.uk> To: Eric Dumazet <edumazet@...gle.com>, syzbot <syzbot+90fd70a665715bd10258@...kaller.appspotmail.com> Cc: davem@...emloft.net, kuba@...nel.org, linux-kernel@...r.kernel.org, netdev@...r.kernel.org, pabeni@...hat.com, syzkaller-bugs@...glegroups.com Subject: Re: [syzbot] [net?] INFO: task hung in nsim_create (2) On 2024-07-24 11:28, Eric Dumazet wrote: > On Wed, Jul 24, 2024 at 8:05 PM syzbot > <syzbot+90fd70a665715bd10258@...kaller.appspotmail.com> wrote: >> >> Hello, >> >> syzbot found the following issue on: >> >> HEAD commit: 68b59730459e Merge tag 'perf-tools-for-v6.11-2024-07-16' o.. >> git tree: upstream >> console output: https://syzkaller.appspot.com/x/log.txt?x=13e0a195980000 >> kernel config: https://syzkaller.appspot.com/x/.config?x=b6230d83d52af231 >> dashboard link: https://syzkaller.appspot.com/bug?extid=90fd70a665715bd10258 >> compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40 >> >> Unfortunately, I don't have any reproducer for this issue yet. >> >> Downloadable assets: >> disk image: https://storage.googleapis.com/syzbot-assets/2ed0d621f118/disk-68b59730.raw.xz >> vmlinux: https://storage.googleapis.com/syzbot-assets/36b453c7acac/vmlinux-68b59730.xz >> kernel image: https://storage.googleapis.com/syzbot-assets/069a896ef41a/bzImage-68b59730.xz >> >> IMPORTANT: if you fix the issue, please add the following tag to the commit: >> Reported-by: syzbot+90fd70a665715bd10258@...kaller.appspotmail.com >> >> INFO: task kworker/u8:5:570 blocked for more than 143 seconds. >> Not tainted 6.10.0-syzkaller-08280-g68b59730459e #0 >> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. >> task:kworker/u8:5 state:D stack:20528 pid:570 tgid:570 ppid:2 flags:0x00004000 >> Workqueue: netns cleanup_net >> Call Trace: >> <TASK> >> context_switch kernel/sched/core.c:5188 [inline] >> __schedule+0x1800/0x4a60 kernel/sched/core.c:6529 >> __schedule_loop kernel/sched/core.c:6606 [inline] >> schedule+0x14b/0x320 kernel/sched/core.c:6621 >> schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6678 >> __mutex_lock_common kernel/locking/mutex.c:684 [inline] >> __mutex_lock+0x6a4/0xd70 kernel/locking/mutex.c:752 This is rtnl_lock(). From stack trace looks like this is triggered when removing the ns that a netdevsim is in. This calls into devlink_pernet_pre_exit() which reloads a devlink (and its associated netdevsim) into the init ns. >> nsim_init_netdevsim drivers/net/netdevsim/netdev.c:678 [inline] >> nsim_create+0x408/0x890 drivers/net/netdevsim/netdev.c:750 >> __nsim_dev_port_add+0x6c0/0xae0 drivers/net/netdevsim/dev.c:1390 >> nsim_dev_port_add_all drivers/net/netdevsim/dev.c:1446 [inline] >> nsim_dev_reload_create drivers/net/netdevsim/dev.c:1498 [inline] >> nsim_dev_reload_up+0x69b/0x8e0 drivers/net/netdevsim/dev.c:985 >> devlink_reload+0x478/0x870 net/devlink/dev.c:474 >> devlink_pernet_pre_exit+0x1f3/0x440 net/devlink/core.c:509 >> ops_pre_exit_list net/core/net_namespace.c:163 [inline] >> cleanup_net+0x615/0xcc0 net/core/net_namespace.c:620 >> process_one_work kernel/workqueue.c:3231 [inline] >> process_scheduled_works+0xa2c/0x1830 kernel/workqueue.c:3312 >> worker_thread+0x86d/0xd40 kernel/workqueue.c:3390 >> 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> >> INFO: task kworker/u8:7:2410 blocked for more than 144 seconds. >> Not tainted 6.10.0-syzkaller-08280-g68b59730459e #0 >> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. >> task:kworker/u8:7 state:D stack:23312 pid:2410 tgid:2410 ppid:2 flags:0x00004000 >> Workqueue: ipv6_addrconf addrconf_dad_work >> Call Trace: >> <TASK> >> context_switch kernel/sched/core.c:5188 [inline] >> __schedule+0x1800/0x4a60 kernel/sched/core.c:6529 >> __schedule_loop kernel/sched/core.c:6606 [inline] >> schedule+0x14b/0x320 kernel/sched/core.c:6621 >> schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6678 >> __mutex_lock_common kernel/locking/mutex.c:684 [inline] >> __mutex_lock+0x6a4/0xd70 kernel/locking/mutex.c:752 This is rtnl_lock() as well. Work is scheduled on a wq in ipv6_add_addr() but not sure what the caller of this is. Can this be called from sysfs? >> addrconf_dad_work+0xd0/0x16f0 net/ipv6/addrconf.c:4194 >> process_one_work kernel/workqueue.c:3231 [inline] >> process_scheduled_works+0xa2c/0x1830 kernel/workqueue.c:3312 >> worker_thread+0x86d/0xd40 kernel/workqueue.c:3390 >> 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> >> INFO: task dhcpcd:4769 blocked for more than 145 seconds. >> Not tainted 6.10.0-syzkaller-08280-g68b59730459e #0 >> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. >> task:dhcpcd state:D >> stack:20384 pid:4769 tgid:4769 ppid:4768 flags:0x00000002 >> Call Trace: >> <TASK> >> context_switch kernel/sched/core.c:5188 [inline] >> __schedule+0x1800/0x4a60 kernel/sched/core.c:6529 >> __schedule_loop kernel/sched/core.c:6606 [inline] >> schedule+0x14b/0x320 kernel/sched/core.c:6621 >> schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6678 >> __mutex_lock_common kernel/locking/mutex.c:684 [inline] >> __mutex_lock+0x6a4/0xd70 kernel/locking/mutex.c:752 >> rtnl_lock net/core/rtnetlink.c:79 [inline] >> rtnetlink_rcv_msg+0x6e6/0xcf0 net/core/rtnetlink.c:6644 >> netlink_rcv_skb+0x1e3/0x430 net/netlink/af_netlink.c:2550 >> netlink_unicast_kernel net/netlink/af_netlink.c:1331 [inline] >> netlink_unicast+0x7f0/0x990 net/netlink/af_netlink.c:1357 >> netlink_sendmsg+0x8e4/0xcb0 net/netlink/af_netlink.c:1901 >> sock_sendmsg_nosec net/socket.c:730 [inline] >> __sock_sendmsg+0x221/0x270 net/socket.c:745 >> ____sys_sendmsg+0x525/0x7d0 net/socket.c:2597 >> ___sys_sendmsg net/socket.c:2651 [inline] >> __sys_sendmsg+0x2b0/0x3a0 net/socket.c:2680 >> do_syscall_x64 arch/x86/entry/common.c:52 [inline] >> do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 >> entry_SYSCALL_64_after_hwframe+0x77/0x7f >> RIP: 0033:0x7f9d6db7da4b >> RSP: 002b:00007ffd2f22e8c8 EFLAGS: 00000246 >> ORIG_RAX: 000000000000002e >> RAX: ffffffffffffffda RBX: 00007f9d6daa56c0 RCX: 00007f9d6db7da4b >> RDX: 0000000000000000 RSI: 00007ffd2f242a78 RDI: 0000000000000005 >> RBP: 0000000000000005 R08: 0000000000000000 R09: 00007ffd2f242a78 >> R10: 0000000000000000 R11: 0000000000000246 R12: ffffffffffffffff >> R13: 00007ffd2f242a78 R14: 0000000000000030 R15: 0000000000000001 >> </TASK> >> INFO: task udevd:5105 blocked for more than 146 seconds. >> Not tainted 6.10.0-syzkaller-08280-g68b59730459e #0 >> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. >> task:udevd state:D >> stack:24864 pid:5105 tgid:5105 ppid:4555 flags:0x00000002 >> Call Trace: >> <TASK> >> context_switch kernel/sched/core.c:5188 [inline] >> __schedule+0x1800/0x4a60 kernel/sched/core.c:6529 >> __schedule_loop kernel/sched/core.c:6606 [inline] >> schedule+0x14b/0x320 kernel/sched/core.c:6621 >> schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6678 >> __mutex_lock_common kernel/locking/mutex.c:684 [inline] >> __mutex_lock+0x6a4/0xd70 kernel/locking/mutex.c:752 This one is taking dev->mutex which is separate to rtnl_mutex. Not sure why this would be blocked too? >> device_lock include/linux/device.h:1009 [inline] >> uevent_show+0x17d/0x340 drivers/base/core.c:2743 >> dev_attr_show+0x55/0xc0 drivers/base/core.c:2437 >> sysfs_kf_seq_show+0x331/0x4c0 fs/sysfs/file.c:59 >> seq_read_iter+0x445/0xd60 fs/seq_file.c:230 >> new_sync_read fs/read_write.c:395 [inline] >> vfs_read+0x9bd/0xbc0 fs/read_write.c:476 >> ksys_read+0x1a0/0x2c0 fs/read_write.c:619 >> do_syscall_x64 arch/x86/entry/common.c:52 [inline] >> do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 >> entry_SYSCALL_64_after_hwframe+0x77/0x7f >> RIP: 0033:0x7fda18b16b6a >> RSP: 002b:00007ffcf336bed8 EFLAGS: 00000246 >> ORIG_RAX: 0000000000000000 >> RAX: ffffffffffffffda RBX: 00005588202d8730 RCX: 00007fda18b16b6a >> RDX: 0000000000001000 RSI: 0000558820307980 RDI: 0000000000000008 >> RBP: 00005588202d8730 R08: 0000000000000008 R09: 0000000000000008 >> R10: 000000000000010f R11: 0000000000000246 R12: 0000000000000000 >> R13: 0000000000003fff R14: 00007ffcf336c3b8 R15: 000000000000000a >> </TASK> >> INFO: task syz-executor:5304 blocked for more than 147 seconds. >> Not tainted 6.10.0-syzkaller-08280-g68b59730459e #0 >> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. >> task:syz-executor state:D stack:20216 pid:5304 tgid:5304 ppid:1 flags:0x00004006 >> Call Trace: >> <TASK> >> context_switch kernel/sched/core.c:5188 [inline] >> __schedule+0x1800/0x4a60 kernel/sched/core.c:6529 >> __schedule_loop kernel/sched/core.c:6606 [inline] >> schedule+0x14b/0x320 kernel/sched/core.c:6621 >> schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6678 >> __mutex_lock_common kernel/locking/mutex.c:684 [inline] >> __mutex_lock+0x6a4/0xd70 kernel/locking/mutex.c:752 >> nsim_destroy+0x71/0x5c0 drivers/net/netdevsim/netdev.c:773 >> __nsim_dev_port_del+0x14b/0x1b0 drivers/net/netdevsim/dev.c:1425 >> nsim_dev_port_del_all drivers/net/netdevsim/dev.c:1437 [inline] >> nsim_dev_reload_destroy+0x28a/0x490 drivers/net/netdevsim/dev.c:1658 >> nsim_drv_remove+0x58/0x160 drivers/net/netdevsim/dev.c:1673 >> device_remove drivers/base/dd.c:566 [inline] >> __device_release_driver drivers/base/dd.c:1270 [inline] >> device_release_driver_internal+0x4a9/0x7c0 drivers/base/dd.c:1293 >> bus_remove_device+0x34f/0x420 drivers/base/bus.c:574 >> device_del+0x57a/0x9b0 drivers/base/core.c:3868 >> device_unregister+0x20/0xc0 drivers/base/core.c:3909 >> nsim_bus_dev_del drivers/net/netdevsim/bus.c:462 [inline] This takes a nsim_bus_dev_list_lock in netdevsim/bus.c. When I wrote this I was careful to ensure the mutexes were nested correctly. The rest of the stack traces are all rtnl_lock. >> del_device_store+0x363/0x480 drivers/net/netdevsim/bus.c:226 >> kernfs_fop_write_iter+0x3a1/0x500 fs/kernfs/file.c:334 >> new_sync_write fs/read_write.c:497 [inline] >> vfs_write+0xa72/0xc90 fs/read_write.c:590 >> ksys_write+0x1a0/0x2c0 fs/read_write.c:643 >> do_syscall_x64 arch/x86/entry/common.c:52 [inline] >> do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 >> entry_SYSCALL_64_after_hwframe+0x77/0x7f >> RIP: 0033:0x7f9e2b3746df >> RSP: 002b:00007f9e2b62f220 EFLAGS: 00000293 >> ORIG_RAX: 0000000000000001 >> RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 00007f9e2b3746df >> RDX: 0000000000000001 RSI: 00007f9e2b62f270 RDI: 0000000000000005 >> RBP: 00007f9e2b3e45b2 R08: 0000000000000000 R09: 00007f9e2b62f077 >> R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000001 >> R13: 00007f9e2b62f270 R14: 00007f9e2c034620 R15: 0000000000000003 >> </TASK> >> INFO: task syz-executor:5325 blocked for more than 148 seconds. >> Not tainted 6.10.0-syzkaller-08280-g68b59730459e #0 >> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. >> task:syz-executor state:D >> stack:21104 pid:5325 tgid:5325 ppid:1 flags:0x00000004 >> Call Trace: >> <TASK> >> context_switch kernel/sched/core.c:5188 [inline] >> __schedule+0x1800/0x4a60 kernel/sched/core.c:6529 >> __schedule_loop kernel/sched/core.c:6606 [inline] >> schedule+0x14b/0x320 kernel/sched/core.c:6621 >> schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6678 >> __mutex_lock_common kernel/locking/mutex.c:684 [inline] >> __mutex_lock+0x6a4/0xd70 kernel/locking/mutex.c:752 >> rtnl_lock net/core/rtnetlink.c:79 [inline] >> rtnetlink_rcv_msg+0x6e6/0xcf0 net/core/rtnetlink.c:6644 >> netlink_rcv_skb+0x1e3/0x430 net/netlink/af_netlink.c:2550 >> netlink_unicast_kernel net/netlink/af_netlink.c:1331 [inline] >> netlink_unicast+0x7f0/0x990 net/netlink/af_netlink.c:1357 >> netlink_sendmsg+0x8e4/0xcb0 net/netlink/af_netlink.c:1901 >> sock_sendmsg_nosec net/socket.c:730 [inline] >> __sock_sendmsg+0x221/0x270 net/socket.c:745 >> __sys_sendto+0x3a4/0x4f0 net/socket.c:2204 >> __do_sys_sendto net/socket.c:2216 [inline] >> __se_sys_sendto net/socket.c:2212 [inline] >> __x64_sys_sendto+0xde/0x100 net/socket.c:2212 >> do_syscall_x64 arch/x86/entry/common.c:52 [inline] >> do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 >> entry_SYSCALL_64_after_hwframe+0x77/0x7f >> RIP: 0033:0x7f1d9e3778ec >> RSP: 002b:00007f1d9e62f630 EFLAGS: 00000293 >> ORIG_RAX: 000000000000002c >> RAX: ffffffffffffffda RBX: 00007f1d9f034620 RCX: 00007f1d9e3778ec >> RDX: 0000000000000020 RSI: 00007f1d9f034670 RDI: 0000000000000003 >> RBP: 0000000000000000 R08: 00007f1d9e62f684 R09: 000000000000000c >> R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000003 >> R13: 0000000000000000 R14: 00007f1d9f034670 R15: 0000000000000000 >> </TASK> >> INFO: task syz-executor:5383 blocked for more than 149 seconds. >> Not tainted 6.10.0-syzkaller-08280-g68b59730459e #0 >> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. >> task:syz-executor state:D >> stack:21728 pid:5383 tgid:5383 ppid:1 flags:0x00000004 >> Call Trace: >> <TASK> >> context_switch kernel/sched/core.c:5188 [inline] >> __schedule+0x1800/0x4a60 kernel/sched/core.c:6529 >> __schedule_loop kernel/sched/core.c:6606 [inline] >> schedule+0x14b/0x320 kernel/sched/core.c:6621 >> schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6678 >> __mutex_lock_common kernel/locking/mutex.c:684 [inline] >> __mutex_lock+0x6a4/0xd70 kernel/locking/mutex.c:752 >> rtnl_lock net/core/rtnetlink.c:79 [inline] >> rtnetlink_rcv_msg+0x6e6/0xcf0 net/core/rtnetlink.c:6644 >> netlink_rcv_skb+0x1e3/0x430 net/netlink/af_netlink.c:2550 >> netlink_unicast_kernel net/netlink/af_netlink.c:1331 [inline] >> netlink_unicast+0x7f0/0x990 net/netlink/af_netlink.c:1357 >> netlink_sendmsg+0x8e4/0xcb0 net/netlink/af_netlink.c:1901 >> sock_sendmsg_nosec net/socket.c:730 [inline] >> __sock_sendmsg+0x221/0x270 net/socket.c:745 >> __sys_sendto+0x3a4/0x4f0 net/socket.c:2204 >> __do_sys_sendto net/socket.c:2216 [inline] >> __se_sys_sendto net/socket.c:2212 [inline] >> __x64_sys_sendto+0xde/0x100 net/socket.c:2212 >> do_syscall_x64 arch/x86/entry/common.c:52 [inline] >> do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 >> entry_SYSCALL_64_after_hwframe+0x77/0x7f >> RIP: 0033:0x7f4baeb778ec >> RSP: 002b:00007f4baee2f6b0 EFLAGS: 00000293 ORIG_RAX: 000000000000002c >> RAX: ffffffffffffffda RBX: 00007f4baf834620 RCX: 00007f4baeb778ec >> RDX: 000000000000003c RSI: 00007f4baf834670 RDI: 0000000000000003 >> RBP: 0000000000000000 R08: 00007f4baee2f704 R09: 000000000000000c >> R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000003 >> R13: 0000000000000000 R14: 00007f4baf834670 R15: 0000000000000000 >> </TASK> >> INFO: task syz.3.62:5420 blocked for more than 150 seconds. >> Not tainted 6.10.0-syzkaller-08280-g68b59730459e #0 >> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. >> task:syz.3.62 state:D stack:22288 pid:5420 tgid:5419 ppid:5118 flags:0x00004006 >> Call Trace: >> <TASK> >> context_switch kernel/sched/core.c:5188 [inline] >> __schedule+0x1800/0x4a60 kernel/sched/core.c:6529 >> __schedule_loop kernel/sched/core.c:6606 [inline] >> schedule+0x14b/0x320 kernel/sched/core.c:6621 >> schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6678 >> __mutex_lock_common kernel/locking/mutex.c:684 [inline] >> __mutex_lock+0x6a4/0xd70 kernel/locking/mutex.c:752 >> netdev_wait_allrefs_any net/core/dev.c:10622 [inline] >> netdev_run_todo+0x7b2/0x1000 net/core/dev.c:10741 >> rtnl_unlock net/core/rtnetlink.c:152 [inline] >> rtnetlink_rcv_msg+0x748/0xcf0 net/core/rtnetlink.c:6648 >> netlink_rcv_skb+0x1e3/0x430 net/netlink/af_netlink.c:2550 >> netlink_unicast_kernel net/netlink/af_netlink.c:1331 [inline] >> netlink_unicast+0x7f0/0x990 net/netlink/af_netlink.c:1357 >> netlink_sendmsg+0x8e4/0xcb0 net/netlink/af_netlink.c:1901 >> sock_sendmsg_nosec net/socket.c:730 [inline] >> __sock_sendmsg+0x221/0x270 net/socket.c:745 >> ____sys_sendmsg+0x525/0x7d0 net/socket.c:2597 >> ___sys_sendmsg net/socket.c:2651 [inline] >> __sys_sendmsg+0x2b0/0x3a0 net/socket.c:2680 >> do_syscall_x64 arch/x86/entry/common.c:52 [inline] >> do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 >> entry_SYSCALL_64_after_hwframe+0x77/0x7f >> RIP: 0033:0x7f5b41f75b59 >> RSP: 002b:00007f5b42cf2048 EFLAGS: 00000246 >> ORIG_RAX: 000000000000002e >> RAX: ffffffffffffffda RBX: 00007f5b42105f60 RCX: 00007f5b41f75b59 >> RDX: 0000000000000000 RSI: 0000000020000140 RDI: 0000000000000006 >> RBP: 00007f5b41fe4e5d R08: 0000000000000000 R09: 0000000000000000 >> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 >> R13: 000000000000000b R14: 00007f5b42105f60 R15: 00007f5b4222fa78 >> </TASK> >> INFO: task syz-executor:5430 blocked for more than 151 seconds. >> Not tainted 6.10.0-syzkaller-08280-g68b59730459e #0 >> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. >> task:syz-executor state:D >> stack:25264 pid:5430 tgid:5430 ppid:1 flags:0x00004004 >> Call Trace: >> <TASK> >> context_switch kernel/sched/core.c:5188 [inline] >> __schedule+0x1800/0x4a60 kernel/sched/core.c:6529 >> __schedule_loop kernel/sched/core.c:6606 [inline] >> schedule+0x14b/0x320 kernel/sched/core.c:6621 >> schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6678 >> __mutex_lock_common kernel/locking/mutex.c:684 [inline] >> __mutex_lock+0x6a4/0xd70 kernel/locking/mutex.c:752 >> register_nexthop_notifier+0x84/0x290 net/ipv4/nexthop.c:3871 >> ops_init+0x359/0x610 net/core/net_namespace.c:139 >> setup_net+0x515/0xca0 net/core/net_namespace.c:343 >> copy_net_ns+0x4e2/0x7b0 net/core/net_namespace.c:508 >> create_new_namespaces+0x425/0x7b0 kernel/nsproxy.c:110 >> unshare_nsproxy_namespaces+0x124/0x180 kernel/nsproxy.c:228 >> ksys_unshare+0x619/0xc10 kernel/fork.c:3308 >> __do_sys_unshare kernel/fork.c:3379 [inline] >> __se_sys_unshare kernel/fork.c:3377 [inline] >> __x64_sys_unshare+0x38/0x40 kernel/fork.c:3377 >> do_syscall_x64 arch/x86/entry/common.c:52 [inline] >> do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 >> entry_SYSCALL_64_after_hwframe+0x77/0x7f >> RIP: 0033:0x7f61f45772b7 >> RSP: 002b:00007f61f482ffa8 EFLAGS: 00000206 ORIG_RAX: 0000000000000110 >> RAX: ffffffffffffffda RBX: 00007f61f45e4bd1 RCX: 00007f61f45772b7 >> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000040000000 >> RBP: 0000000000000000 R08: 00007f61f5237d60 R09: 0000000000000000 >> R10: 0000000000000000 R11: 0000000000000206 R12: 000000000000000c >> R13: 0000000000000003 R14: 0000000000000009 R15: 0000000000000009 >> </TASK> >> INFO: task syz-executor:5432 blocked for more than 152 seconds. >> Not tainted 6.10.0-syzkaller-08280-g68b59730459e #0 >> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. >> task:syz-executor state:D >> stack:25712 pid:5432 tgid:5432 ppid:1 flags:0x00004006 >> Call Trace: >> <TASK> >> context_switch kernel/sched/core.c:5188 [inline] >> __schedule+0x1800/0x4a60 kernel/sched/core.c:6529 >> __schedule_loop kernel/sched/core.c:6606 [inline] >> schedule+0x14b/0x320 kernel/sched/core.c:6621 >> schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6678 >> __mutex_lock_common kernel/locking/mutex.c:684 [inline] >> __mutex_lock+0x6a4/0xd70 kernel/locking/mutex.c:752 >> register_nexthop_notifier+0x84/0x290 net/ipv4/nexthop.c:3871 >> ops_init+0x359/0x610 net/core/net_namespace.c:139 >> setup_net+0x515/0xca0 net/core/net_namespace.c:343 >> copy_net_ns+0x4e2/0x7b0 net/core/net_namespace.c:508 >> create_new_namespaces+0x425/0x7b0 kernel/nsproxy.c:110 >> unshare_nsproxy_namespaces+0x124/0x180 kernel/nsproxy.c:228 >> ksys_unshare+0x619/0xc10 kernel/fork.c:3308 >> >> >> --- >> 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 syzkaller@...glegroups.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 to overwrite report's subsystems, reply with: >> #syz set subsystems: new-subsystem >> (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 > > The fact that netdevsim uses a sysfs file to add/delete netdevice > seems unfortunate, > because of the classical sysfs vs rtnl issue (see rtnl_trylock() calls > in net/core/net-sysfs.c for reference) Hi Eric, what is the classical sysfs vs rtnl issue? Is it a race, AA/ABBA deadlock, or just slowness due to contention on rtnl_mutex? This thread [1] says it is a deadlock. I found this commit 5a5990d3 net: Avoid race between network down and sysfs, but the description doesn't go into detail what exactly the race is. Would using Netlink API for doing netdevsim operations solve the issue? [1]: https://lore.kernel.org/netdev/20231018154804.420823-1-atenart@kernel.org/
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