bisecting fixing commit since 2034d6f0838e465dd8f120c4e946d8444b4bb5df building syzkaller on 6a81331a1d4c744da9204d02ec88d558f7eea9c9 testing commit 2034d6f0838e465dd8f120c4e946d8444b4bb5df compiler: gcc version 8.4.1 20210217 (GCC) kernel signature: a959443498d12a176eb08b7ee86228a9880f87974065c005fff2e7dff1543503 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 addrconf_rs_timer 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 c2276d585654e8d573366c29c565043ec36adf63 testing commit c2276d585654e8d573366c29c565043ec36adf63 compiler: gcc version 8.4.1 20210217 (GCC) kernel signature: 38e78e2a02284097c9794df4e08efae5bde1e78f8d4f5a2ac614981a15bf3056 run #0: crashed: BUG: soft lockup in netlink_sendmsg run #1: crashed: BUG: soft lockup in addrconf_rs_timer 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 revisions tested: 2, total time: 35m57.001275502s (build: 16m35.963134505s, test: 18m56.878893624s) the crash still happens on HEAD commit msg: Linux 4.19.208 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-executor588:4103] Modules linked in: irq event stamp: 924133 hardirqs last enabled at (924132): [] seqcount_lockdep_reader_access include/linux/seqlock.h:83 [inline] hardirqs last enabled at (924132): [] read_seqcount_begin include/linux/seqlock.h:164 [inline] hardirqs last enabled at (924132): [] ktime_get kernel/time/timekeeping.c:756 [inline] hardirqs last enabled at (924132): [] ktime_get+0x1a0/0x230 kernel/time/timekeeping.c:746 hardirqs last disabled at (924133): [] trace_hardirqs_off_thunk+0x1a/0x1c softirqs last enabled at (68): [] spin_unlock_bh include/linux/spinlock.h:374 [inline] softirqs last enabled at (68): [] release_sock+0x11f/0x180 net/core/sock.c:2892 softirqs last disabled at (76): [] __dev_queue_xmit+0x20b/0x2900 net/core/dev.c:3773 CPU: 0 PID: 4103 Comm: syz-executor588 Not tainted 4.19.208-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+0x123/0x300 net/sched/sch_cake.c:1383 Code: f2 4c 89 ff e8 0e fc ff ff 44 89 f2 43 8d 04 36 8d 70 01 83 c0 02 81 fe ff 1f 00 00 0f 87 96 00 00 00 48 63 de 49 8d 7c 5f 18 <49> 89 f8 49 c1 e8 03 47 0f b6 0c 28 49 89 f8 41 83 e0 07 41 83 c0 RSP: 0018:ffff8880915674b8 EFLAGS: 00000293 ORIG_RAX: ffffffffffffff13 RAX: 0000000000000aa8 RBX: 0000000000000aa7 RCX: 0000000000000017 RDX: 0000000000000553 RSI: 0000000000000aa7 RDI: ffff88809f284326 RBP: ffff8880915674f0 R08: 0000000000000000 R09: 0000000000000000 R10: fffffbfff15df601 R11: 0000000093332bbc R12: 00000000000000aa R13: dffffc0000000000 R14: 0000000000000553 R15: ffff88809f282dc0 FS: 00007fcb2dbd9700(0000) GS:ffff8880ba200000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 00000000a8486000 CR4: 00000000003406f0 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:2227 __sys_sendmsg+0xd9/0x180 net/socket.c:2265 __do_sys_sendmsg net/socket.c:2274 [inline] __se_sys_sendmsg net/socket.c:2272 [inline] __x64_sys_sendmsg+0x73/0xb0 net/socket.c:2272 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x7fcb2e455ae9 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:00007fcb2dbd9318 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007fcb2e4d84b8 RCX: 00007fcb2e455ae9 RDX: 0000000000000000 RSI: 00000000200001c0 RDI: 0000000000000005 RBP: 00007fcb2e4d84b0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007fcb2e4a47d8 R13: 00007fff73a645bf R14: 00007fcb2dbd9400 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 ---------------- Code disassembly (best guess): 0: f2 4c 89 ff repnz mov %r15,%rdi 4: e8 0e fc ff ff callq 0xfffffc17 9: 44 89 f2 mov %r14d,%edx c: 43 8d 04 36 lea (%r14,%r14,1),%eax 10: 8d 70 01 lea 0x1(%rax),%esi 13: 83 c0 02 add $0x2,%eax 16: 81 fe ff 1f 00 00 cmp $0x1fff,%esi 1c: 0f 87 96 00 00 00 ja 0xb8 22: 48 63 de movslq %esi,%rbx 25: 49 8d 7c 5f 18 lea 0x18(%r15,%rbx,2),%rdi * 2a: 49 89 f8 mov %rdi,%r8 <-- trapping instruction 2d: 49 c1 e8 03 shr $0x3,%r8 31: 47 0f b6 0c 28 movzbl (%r8,%r13,1),%r9d 36: 49 89 f8 mov %rdi,%r8 39: 41 83 e0 07 and $0x7,%r8d 3d: 41 rex.B 3e: 83 .byte 0x83 3f: c0 .byte 0xc0