bisecting fixing commit since 2034d6f0838e465dd8f120c4e946d8444b4bb5df building syzkaller on 6a81331a1d4c744da9204d02ec88d558f7eea9c9 testing commit 2034d6f0838e465dd8f120c4e946d8444b4bb5df with gcc (GCC) 8.4.1 20210217 kernel signature: db37f47429e58fad1494f9707a1f902c6c1d934ff19572243c93a25415ad2039 all runs: crashed: BUG: soft lockup in netlink_sendmsg testing current HEAD 6b7b0056defc6eb5c87bbe4690ccda547b2891aa testing commit 6b7b0056defc6eb5c87bbe4690ccda547b2891aa with gcc (GCC) 8.4.1 20210217 kernel signature: 0ce2ff5fd968e6f872e1df1f267a8ce71f2042b47b594930a39002693d9fbefd all runs: crashed: BUG: soft lockup in netlink_sendmsg revisions tested: 2, total time: 28m59.230776462s (build: 15m0.345485031s, test: 13m38.519139389s) the crash still happens on HEAD commit msg: Linux 4.19.192 crash: BUG: soft lockup in netlink_sendmsg IPv6: ADDRCONF(NETDEV_CHANGE): wlan1: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): wlan1: link becomes ready wlan1: Creating new IBSS network, BSSID 50:50:50:50:50:50 IPv6: ADDRCONF(NETDEV_CHANGE): wlan1: link becomes ready watchdog: BUG: soft lockup - CPU#0 stuck for 22s! [syz-executor.1:10068] Modules linked in: irq event stamp: 935751 hardirqs last enabled at (935750): [] seqcount_lockdep_reader_access include/linux/seqlock.h:83 [inline] hardirqs last enabled at (935750): [] read_seqcount_begin include/linux/seqlock.h:164 [inline] hardirqs last enabled at (935750): [] ktime_get kernel/time/timekeeping.c:756 [inline] hardirqs last enabled at (935750): [] ktime_get+0x1a0/0x230 kernel/time/timekeeping.c:746 hardirqs last disabled at (935751): [] trace_hardirqs_off_thunk+0x1a/0x1c softirqs last enabled at (526): [] spin_unlock_bh include/linux/spinlock.h:374 [inline] softirqs last enabled at (526): [] release_sock+0x11f/0x180 net/core/sock.c:2892 softirqs last disabled at (534): [] __dev_queue_xmit+0x20b/0x2900 net/core/dev.c:3773 CPU: 0 PID: 10068 Comm: syz-executor.1 Not tainted 4.19.192-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:cake_drop net/sched/sch_cake.c:1468 [inline] RIP: 0010:cake_enqueue+0x1181/0x3b00 net/sched/sch_cake.c:1844 Code: 38 84 c0 74 08 3c 01 0f 8e 28 1a 00 00 66 41 83 be 98 42 00 00 00 75 1c bb 00 10 00 00 48 8b bc 24 b0 00 00 00 89 de 83 eb 01 1a d8 fe ff 83 fb ff 75 e9 48 8b 44 24 70 41 ba ff ff ff ff 66 RSP: 0018:ffff88807da0f500 EFLAGS: 00000206 ORIG_RAX: ffffffffffffff13 RAX: 0000000000001072 RBX: 0000000000000836 RCX: 0000000000000017 RDX: 0000000000000838 RSI: 0000000000000837 RDI: ffff88807da813c0 RBP: ffff88807da0f650 R08: 0000000000000000 R09: 0000000000000000 R10: fffffbfff15df401 R11: 000000009d89af19 R12: 00000013f9f2ce99 R13: 0000000000000000 R14: ffff88807da81140 R15: dffffc0000000000 FS: 00007feb02648700(0000) GS:ffff8880ba200000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 000000009ab43000 CR4: 00000000001406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __dev_xmit_skb net/core/dev.c:3494 [inline] __dev_queue_xmit+0x1098/0x2900 net/core/dev.c:3807 dev_queue_xmit+0xb/0x10 net/core/dev.c:3871 __netlink_deliver_tap_skb net/netlink/af_netlink.c:303 [inline] __netlink_deliver_tap net/netlink/af_netlink.c:321 [inline] netlink_deliver_tap+0x77e/0xb00 net/netlink/af_netlink.c:334 netlink_deliver_tap_kernel net/netlink/af_netlink.c:343 [inline] netlink_unicast_kernel net/netlink/af_netlink.c:1317 [inline] netlink_unicast+0x412/0x660 net/netlink/af_netlink.c:1344 netlink_sendmsg+0x667/0xc60 net/netlink/af_netlink.c:1909 sock_sendmsg_nosec net/socket.c:622 [inline] sock_sendmsg+0xac/0xf0 net/socket.c:632 ___sys_sendmsg+0x647/0x950 net/socket.c:2115 __sys_sendmsg+0xd9/0x180 net/socket.c:2153 __do_sys_sendmsg net/socket.c:2162 [inline] __se_sys_sendmsg net/socket.c:2160 [inline] __x64_sys_sendmsg+0x73/0xb0 net/socket.c:2160 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x466459 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 bc ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007feb02648188 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 0000000000466459 RDX: 0000000000000000 RSI: 00000000200001c0 RDI: 0000000000000005 RBP: 00000000004bf9fb R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf60 R13: 00007ffc66e8409f R14: 00007feb02648300 R15: 0000000000022000 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 CPU: 1 PID: 10074 Comm: syz-executor.1 Not tainted 4.19.192-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:pv_wait_head_or_lock kernel/locking/qspinlock_paravirt.h:435 [inline] RIP: 0010:__pv_queued_spin_lock_slowpath+0x3e2/0xc00 kernel/locking/qspinlock.c:474 Code: c6 45 01 01 48 b8 00 00 00 00 00 fc ff df 48 c1 e9 03 41 be 00 80 00 00 41 83 e4 07 48 8d 1c 01 41 bf 01 00 00 00 eb 0c f3 90 <41> 83 ee 01 0f 84 85 04 00 00 0f b6 03 44 38 e0 7f 08 84 c0 0f 85 RSP: 0018:ffff88807e567528 EFLAGS: 00000206 RAX: 0000000000000003 RBX: ffffed100fb50245 RCX: 1ffff1100fb50245 RDX: 1ffffffff1322499 RSI: dffffc0000000000 RDI: 0000000000000282 RBP: ffff88807e5675f8 R08: ffff8880b2946db8 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000 R13: ffff88807da81228 R14: 0000000000001239 R15: 0000000000000001 FS: 00007feb02627700(0000) GS:ffff8880ba300000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007feb02606718 CR3: 000000009ab43000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:679 [inline] queued_spin_lock_slowpath arch/x86/include/asm/qspinlock.h:53 [inline] queued_spin_lock include/asm-generic/qspinlock.h:88 [inline] do_raw_spin_lock+0x1a5/0x240 kernel/locking/spinlock_debug.c:113 __raw_spin_lock include/linux/spinlock_api_smp.h:143 [inline] _raw_spin_lock+0x35/0x40 kernel/locking/spinlock.c:144 spin_lock include/linux/spinlock.h:329 [inline] __dev_xmit_skb net/core/dev.c:3469 [inline] __dev_queue_xmit+0x100b/0x2900 net/core/dev.c:3807 dev_queue_xmit+0xb/0x10 net/core/dev.c:3871 __netlink_deliver_tap_skb net/netlink/af_netlink.c:303 [inline] __netlink_deliver_tap net/netlink/af_netlink.c:321 [inline] netlink_deliver_tap+0x77e/0xb00 net/netlink/af_netlink.c:334 netlink_deliver_tap_kernel net/netlink/af_netlink.c:343 [inline] netlink_unicast_kernel net/netlink/af_netlink.c:1317 [inline] netlink_unicast+0x412/0x660 net/netlink/af_netlink.c:1344 netlink_sendmsg+0x667/0xc60 net/netlink/af_netlink.c:1909 sock_sendmsg_nosec net/socket.c:622 [inline] sock_sendmsg+0xac/0xf0 net/socket.c:632 ___sys_sendmsg+0x647/0x950 net/socket.c:2115 __sys_sendmsg+0xd9/0x180 net/socket.c:2153 __do_sys_sendmsg net/socket.c:2162 [inline] __se_sys_sendmsg net/socket.c:2160 [inline] __x64_sys_sendmsg+0x73/0xb0 net/socket.c:2160 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x466459 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 bc ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007feb02627188 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 000000000056c008 RCX: 0000000000466459 RDX: 0000000000000000 RSI: 00000000200007c0 RDI: 0000000000000003 RBP: 00000000004bf9fb R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056c008 R13: 00007ffc66e8409f R14: 00007feb02627300 R15: 0000000000022000