bisecting fixing commit since 2034d6f0838e465dd8f120c4e946d8444b4bb5df building syzkaller on 6a81331a1d4c744da9204d02ec88d558f7eea9c9 testing commit 2034d6f0838e465dd8f120c4e946d8444b4bb5df compiler: gcc version 8.4.1 20210217 (GCC) kernel signature: 7b818b266dffa0bb9aa98e907d371d978169d0efd635bf6543268cebd9d676ea run #0: crashed: BUG: soft lockup in netlink_sendmsg run #1: crashed: BUG: soft lockup in netlink_sendmsg run #2: crashed: BUG: soft lockup in netlink_sendmsg run #3: crashed: BUG: soft lockup in netlink_sendmsg run #4: crashed: BUG: soft lockup in netlink_sendmsg run #5: crashed: BUG: soft lockup in netlink_sendmsg run #6: crashed: BUG: soft lockup in netlink_sendmsg run #7: crashed: BUG: soft lockup in netlink_sendmsg run #8: crashed: BUG: soft lockup in netlink_sendmsg run #9: crashed: BUG: soft lockup in netlink_sendmsg run #10: crashed: BUG: soft lockup in netlink_sendmsg run #11: crashed: BUG: soft lockup in netlink_sendmsg run #12: crashed: BUG: soft lockup in netlink_sendmsg run #13: crashed: BUG: soft lockup in netlink_sendmsg run #14: crashed: BUG: soft lockup in netlink_sendmsg run #15: crashed: BUG: soft lockup in netlink_sendmsg run #16: crashed: BUG: soft lockup in addrconf_rs_timer run #17: crashed: BUG: soft lockup in netlink_sendmsg run #18: crashed: BUG: soft lockup in netlink_sendmsg run #19: crashed: BUG: soft lockup in netlink_sendmsg testing current HEAD e23d55af0e1fca9be5c99f0c37d48b289f4d6489 testing commit e23d55af0e1fca9be5c99f0c37d48b289f4d6489 compiler: gcc version 8.4.1 20210217 (GCC) kernel signature: aaf6e8c5d85dc26d0adb9dd2219a8caec0179724adbc0cfc65545def8d8fa715 all runs: crashed: BUG: soft lockup in netlink_sendmsg revisions tested: 2, total time: 38m30.947630371s (build: 18m43.630720494s, test: 19m5.603345797s) the crash still happens on HEAD commit msg: Linux 4.19.205 crash: BUG: soft lockup in netlink_sendmsg IPv6: ADDRCONF(NETDEV_CHANGE): veth0_to_batadv: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): macvtap0: link becomes ready batman_adv: batadv0: Interface activated: batadv_slave_1 IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_batadv: link becomes ready watchdog: BUG: soft lockup - CPU#1 stuck for 22s! [syz-executor088:10062] Modules linked in: irq event stamp: 662793 hardirqs last enabled at (662792): [] seqcount_lockdep_reader_access include/linux/seqlock.h:83 [inline] hardirqs last enabled at (662792): [] read_seqcount_begin include/linux/seqlock.h:164 [inline] hardirqs last enabled at (662792): [] ktime_get kernel/time/timekeeping.c:756 [inline] hardirqs last enabled at (662792): [] ktime_get+0x1a0/0x230 kernel/time/timekeeping.c:746 hardirqs last disabled at (662793): [] trace_hardirqs_off_thunk+0x1a/0x1c softirqs last enabled at (62): [] spin_unlock_bh include/linux/spinlock.h:374 [inline] softirqs last enabled at (62): [] release_sock+0x11f/0x180 net/core/sock.c:2892 softirqs last disabled at (70): [] __dev_queue_xmit+0x20b/0x2900 net/core/dev.c:3773 CPU: 1 PID: 10062 Comm: syz-executor088 Not tainted 4.19.205-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:cake_heap_get_backlog net/sched/sch_cake.c:1369 [inline] RIP: 0010:cake_heapify+0x180/0x300 net/sched/sch_cake.c:1383 Code: 5f 08 41 83 e4 07 4d 69 e4 d8 98 01 00 66 c1 eb 03 4d 03 67 10 81 e3 ff 03 00 00 49 8d bc 9c 00 40 01 00 49 89 f8 49 c1 e8 03 <47> 0f b6 0c 28 49 89 f8 41 83 e0 07 41 83 c0 03 45 38 c8 7c 09 45 RSP: 0018:ffff8880b4a074b8 EFLAGS: 00000a06 ORIG_RAX: ffffffffffffff13 RAX: 0000000000001138 RBX: 0000000000000226 RCX: 0000000000000017 RDX: 000000000000089b RSI: 0000000000001137 RDI: ffff88806b8c95c0 RBP: ffff8880b4a074f0 R08: 1ffff1100d7192b8 R09: 0000000000000000 R10: fffffbfff15df609 R11: 0000000090a10a3f R12: ffff88806b8b4d28 R13: dffffc0000000000 R14: 000000000000089b R15: ffff888070362fc0 FS: 00007fc7f52bc700(0000) GS:ffff8880ba300000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 0000000090daf000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: cake_drop net/sched/sch_cake.c:1472 [inline] cake_enqueue+0x1186/0x3b00 net/sched/sch_cake.c:1848 __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:1319 [inline] netlink_unicast+0x412/0x660 net/netlink/af_netlink.c:1346 netlink_sendmsg+0x667/0xc60 net/netlink/af_netlink.c:1911 sock_sendmsg_nosec net/socket.c:651 [inline] sock_sendmsg+0xac/0xf0 net/socket.c:661 ___sys_sendmsg+0x647/0x950 net/socket.c:2225 __sys_sendmsg+0xd9/0x180 net/socket.c:2263 __do_sys_sendmsg net/socket.c:2272 [inline] __se_sys_sendmsg net/socket.c:2270 [inline] __x64_sys_sendmsg+0x73/0xb0 net/socket.c:2270 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x4519a9 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 91 18 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:00007fc7f52bc318 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00000000004d04d8 RCX: 00000000004519a9 RDX: 0000000000000000 RSI: 00000000200001c0 RDI: 0000000000000005 RBP: 00000000004d04d0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000049f7d8 R13: 00007fff8b5f74af R14: 00007fc7f52bc400 R15: 0000000000022000 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 PID: 10063 Comm: syz-executor088 Not tainted 4.19.205-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:ffff8880a8aef528 EFLAGS: 00000206 RAX: 0000000000000003 RBX: ffffed100e06c5c5 RCX: 1ffff1100e06c5c5 RDX: 1ffffffff13224a9 RSI: dffffc0000000000 RDI: 0000000000000286 RBP: ffff8880a8aef5f8 R08: ffff8880b29a0db8 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000 R13: ffff888070362e28 R14: 0000000000006722 R15: 0000000000000001 FS: 00007fc7f529b700(0000) GS:ffff8880ba200000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fc7f529b718 CR3: 0000000090daf000 CR4: 00000000001406f0 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:1319 [inline] netlink_unicast+0x412/0x660 net/netlink/af_netlink.c:1346 netlink_sendmsg+0x667/0xc60 net/netlink/af_netlink.c:1911 sock_sendmsg_nosec net/socket.c:651 [inline] sock_sendmsg+0xac/0xf0 net/socket.c:661 ___sys_sendmsg+0x647/0x950 net/socket.c:2225 __sys_sendmsg+0xd9/0x180 net/socket.c:2263 __do_sys_sendmsg net/socket.c:2272 [inline] __se_sys_sendmsg net/socket.c:2270 [inline] __x64_sys_sendmsg+0x73/0xb0 net/socket.c:2270 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x4519a9 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 91 18 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:00007fc7f529b318 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00000000004d04e8 RCX: 00000000004519a9 RDX: 0000000000000000 RSI: 00000000200007c0 RDI: 0000000000000003 RBP: 00000000004d04e0 R08: 00007fc7f529b700 R09: 0000000000000000 R10: 00007fc7f529b700 R11: 0000000000000246 R12: 000000000049f7d8 R13: 00007fff8b5f74af R14: 00007fc7f529b400 R15: 0000000000022000 ---------------- Code disassembly (best guess): 0: 5f pop %rdi 1: 08 41 83 or %al,-0x7d(%rcx) 4: e4 07 in $0x7,%al 6: 4d 69 e4 d8 98 01 00 imul $0x198d8,%r12,%r12 d: 66 c1 eb 03 shr $0x3,%bx 11: 4d 03 67 10 add 0x10(%r15),%r12 15: 81 e3 ff 03 00 00 and $0x3ff,%ebx 1b: 49 8d bc 9c 00 40 01 lea 0x14000(%r12,%rbx,4),%rdi 22: 00 23: 49 89 f8 mov %rdi,%r8 26: 49 c1 e8 03 shr $0x3,%r8 * 2a: 47 0f b6 0c 28 movzbl (%r8,%r13,1),%r9d <-- trapping instruction 2f: 49 89 f8 mov %rdi,%r8 32: 41 83 e0 07 and $0x7,%r8d 36: 41 83 c0 03 add $0x3,%r8d 3a: 45 38 c8 cmp %r9b,%r8b 3d: 7c 09 jl 0x48 3f: 45 rex.RB