bisecting fixing commit since 2034d6f0838e465dd8f120c4e946d8444b4bb5df building syzkaller on 6a81331a1d4c744da9204d02ec88d558f7eea9c9 testing commit 2034d6f0838e465dd8f120c4e946d8444b4bb5df compiler: gcc version 8.4.1 20210217 (GCC) kernel signature: 1ef574720de816aa5c67b23105e55cdc1528b5cc37348debeb05d6c9da9b8cab 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 addrconf_rs_timer 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 netlink_sendmsg 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 53bd76690e27f37c9df221a651a52cea04214da9 testing commit 53bd76690e27f37c9df221a651a52cea04214da9 compiler: gcc version 8.4.1 20210217 (GCC) kernel signature: cbcb9adf072befd4e91018e3ec5191ff4598bf7fbd44b6b93769ad3d649e9eb2 all runs: crashed: BUG: soft lockup in netlink_sendmsg revisions tested: 2, total time: 35m22.718943398s (build: 15m49.938333325s, test: 19m9.720033654s) the crash still happens on HEAD commit msg: Linux 4.19.200 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#0 stuck for 22s! [syz-executor683:5088] Modules linked in: irq event stamp: 812501 hardirqs last enabled at (812500): [] seqcount_lockdep_reader_access include/linux/seqlock.h:83 [inline] hardirqs last enabled at (812500): [] read_seqcount_begin include/linux/seqlock.h:164 [inline] hardirqs last enabled at (812500): [] ktime_get kernel/time/timekeeping.c:756 [inline] hardirqs last enabled at (812500): [] ktime_get+0x1a0/0x230 kernel/time/timekeeping.c:746 hardirqs last disabled at (812501): [] 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: 0 PID: 5088 Comm: syz-executor683 Not tainted 4.19.200-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:1367 [inline] RIP: 0010:cake_heapify+0x32/0x300 net/sched/sch_cake.c:1375 Code: ff df 55 89 f2 48 89 e5 41 57 49 89 ff 41 56 41 55 41 54 53 0f b7 de 48 8d 7c 5f 18 48 83 ec 10 49 89 de 48 89 fe 48 c1 ee 03 <0f> b6 34 06 48 89 f8 83 e0 07 83 c0 01 40 38 f0 7c 09 40 84 f6 0f RSP: 0018:ffff8880b52bf4b8 EFLAGS: 00000a02 ORIG_RAX: ffffffffffffff13 RAX: dffffc0000000000 RBX: 00000000000001e0 RCX: 0000000000000017 RDX: 00000000000001e0 RSI: 1ffff110128e463b RDI: ffff8880947231d8 RBP: ffff8880b52bf4f0 R08: 0000000000000000 R09: 0000000000000000 R10: fffffbfff15df801 R11: 00000000977371ba R12: 00000064f65b51e5 R13: 0000000000000000 R14: 00000000000001e0 R15: ffff888094722e00 FS: 00007f26138a9700(0000) GS:ffff8880ba200000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 000000009d3f5000 CR4: 00000000001406f0 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:00007f26138a9318 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: 00007ffd53011d7f R14: 00007f26138a9400 R15: 0000000000022000 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 skipped: idling at native_safe_halt+0x12/0x20 arch/x86/include/asm/irqflags.h:60