bisecting cause commit starting from d5ae8d7f85b7f6f6e60f1af8ff4be52b0926fde1 building syzkaller on b599f2fcc734e2183016a340d4f6fc2891d8e41f testing commit d5ae8d7f85b7f6f6e60f1af8ff4be52b0926fde1 compiler: gcc (GCC) 10.2.1 20210217, GNU ld (GNU Binutils for Debian) 2.35.1 kernel signature: 06405285481b58ab27fcc61b26bfaa376a940908f41e640ff7cdd921e807428a run #0: crashed: INFO: task hung in do_proc_bulk run #1: crashed: INFO: task hung in do_proc_bulk run #2: crashed: INFO: task hung in do_proc_bulk run #3: crashed: INFO: task hung in do_proc_bulk run #4: crashed: INFO: task hung in do_proc_bulk run #5: crashed: INFO: task hung in do_proc_bulk run #6: crashed: INFO: task hung in do_proc_bulk run #7: crashed: INFO: task hung in do_proc_bulk run #8: crashed: INFO: task hung in do_proc_bulk run #9: crashed: INFO: task hung in do_proc_bulk run #10: crashed: INFO: task hung in do_proc_bulk run #11: OK run #12: OK run #13: OK run #14: OK run #15: OK run #16: OK run #17: OK run #18: OK run #19: OK testing release v5.13 testing commit 62fb9874f5da54fdb243003b386128037319b219 compiler: gcc (GCC) 10.2.1 20210217, GNU ld (GNU Binutils for Debian) 2.35.1 kernel signature: eaab50170f966c8b3eb39852b91e95d9bc7e454d96827a490e5a435720d1ffbe run #0: crashed: INFO: task hung in do_proc_bulk run #1: crashed: INFO: task hung in do_proc_bulk run #2: crashed: INFO: task hung in do_proc_bulk run #3: crashed: INFO: task hung in do_proc_bulk run #4: crashed: INFO: task hung in do_proc_bulk run #5: crashed: INFO: task hung in do_proc_bulk run #6: OK run #7: OK run #8: OK run #9: OK testing release v5.12 testing commit 9f4ad9e425a1d3b6a34617b8ea226d56a119a717 compiler: gcc (GCC) 10.2.1 20210217, GNU ld (GNU Binutils for Debian) 2.35.1 kernel signature: a2c67d0aa4cd9031fb2dccc0e9429d13c38be324308c26aa1ef6b084265ddb79 run #0: crashed: INFO: task hung in do_proc_bulk run #1: crashed: INFO: task hung in do_proc_bulk run #2: crashed: INFO: task hung in do_proc_bulk run #3: crashed: INFO: task hung in do_proc_bulk run #4: crashed: INFO: task hung in do_proc_bulk run #5: OK run #6: OK run #7: OK run #8: OK run #9: OK testing release v5.11 testing commit f40ddce88593482919761f74910f42f4b84c004b compiler: gcc (GCC) 10.2.1 20210217, GNU ld (GNU Binutils for Debian) 2.35.1 kernel signature: 760afc9eb3d03287b34ea942b7a411382f5645571be3e022de43df2d69784b74 run #0: crashed: INFO: task hung in do_proc_bulk run #1: crashed: INFO: task hung in do_proc_bulk run #2: crashed: INFO: task hung in do_proc_bulk run #3: crashed: INFO: task hung in do_proc_bulk run #4: crashed: INFO: task hung in do_proc_bulk run #5: crashed: INFO: task hung in do_proc_bulk run #6: OK run #7: OK run #8: OK run #9: OK testing release v5.10 testing commit 2c85ebc57b3e1817b6ce1a6b703928e113a90442 compiler: gcc (GCC) 10.2.1 20210217, GNU ld (GNU Binutils for Debian) 2.35.1 kernel signature: ed87a01106570e960457a093defc61da2463f8df499a22d92a19e05b34bca040 run #0: crashed: INFO: task hung in do_proc_bulk run #1: crashed: INFO: task hung in do_proc_bulk run #2: crashed: INFO: task hung in do_proc_bulk run #3: crashed: INFO: task hung in do_proc_bulk run #4: crashed: INFO: task hung in do_proc_bulk run #5: crashed: INFO: task hung in do_proc_bulk run #6: crashed: INFO: task hung in do_proc_bulk run #7: OK run #8: OK run #9: OK testing release v5.9 testing commit bbf5c979011a099af5dc76498918ed7df445635b compiler: gcc (GCC) 10.2.1 20210217, GNU ld (GNU Binutils for Debian) 2.35.1 kernel signature: a6ff38e82dd9e7b72f8594f21d4456e9f130fed2d0baffe8f9a1ac831a8846b8 run #0: crashed: INFO: task hung in do_proc_bulk run #1: crashed: INFO: task hung in do_proc_bulk run #2: crashed: INFO: task hung in do_proc_bulk run #3: crashed: INFO: task hung in do_proc_bulk run #4: crashed: INFO: task hung in do_proc_bulk run #5: crashed: INFO: task hung in do_proc_bulk run #6: OK run #7: OK run #8: OK run #9: OK testing release v5.8 testing commit bcf876870b95592b52519ed4aafcf9d95999bc9c compiler: gcc (GCC) 8.4.1 20210217, GNU ld (GNU Binutils for Debian) 2.35.1 kernel signature: 148af9454d2419d8c534f359dc0ada77e2a0b73e26499bd1d569517b33bb77e1 run #0: crashed: INFO: task hung in proc_bulk run #1: crashed: INFO: task hung in proc_bulk run #2: crashed: INFO: task hung in proc_bulk run #3: crashed: INFO: task hung in proc_bulk run #4: crashed: INFO: task hung in proc_bulk run #5: OK run #6: OK run #7: OK run #8: OK run #9: OK testing release v5.7 testing commit 3d77e6a8804abcc0504c904bd6e5cdf3a5cf8162 compiler: gcc version 8.4.1 20210217 (GCC), GNU ld (GNU Binutils for Debian) 2.35.1 kernel signature: c39813ac1b4cf9ee17cd9581d29834c9312d7a9e2d37c5149682cd29e326d445 run #0: crashed: INFO: task hung in proc_bulk run #1: crashed: INFO: task hung in proc_bulk run #2: crashed: INFO: task hung in proc_bulk run #3: crashed: INFO: task hung in proc_bulk run #4: crashed: INFO: task hung in proc_bulk run #5: crashed: INFO: task hung in proc_bulk run #6: OK run #7: OK run #8: OK run #9: OK testing release v5.6 testing commit 7111951b8d4973bda27ff663f2cf18b663d15b48 compiler: gcc version 8.4.1 20210217 (GCC) kernel signature: 65e9f41c1707ffe281e68adea77024db743fc3aec52e15a3092851b775aa1091 run #0: crashed: INFO: task hung in proc_bulk run #1: crashed: INFO: task hung in proc_bulk run #2: crashed: INFO: task hung in proc_bulk run #3: crashed: INFO: task hung in proc_bulk run #4: crashed: INFO: task hung in proc_bulk run #5: crashed: INFO: task hung in proc_bulk run #6: crashed: INFO: task hung in proc_bulk run #7: OK run #8: OK run #9: crashed: INFO: task hung in proc_bulk testing release v5.5 testing commit d5226fa6dbae0569ee43ecfc08bdcd6770fc4755 compiler: gcc version 8.4.1 20210217 (GCC) kernel signature: df229a265ef77d7ea04c00e82025c3f1c0476396510a270bc6ec4e905f5dd17e run #0: crashed: INFO: task hung in proc_bulk run #1: crashed: INFO: task hung in proc_bulk run #2: crashed: INFO: task hung in proc_bulk run #3: crashed: INFO: task hung in proc_bulk run #4: crashed: INFO: task hung in proc_bulk run #5: crashed: INFO: task hung in proc_bulk run #6: crashed: INFO: task hung in proc_bulk run #7: crashed: INFO: task hung in proc_bulk run #8: OK run #9: OK testing release v5.4 testing commit 219d54332a09e8d8741c1e1982f5eae56099de85 compiler: gcc version 8.4.1 20210217 (GCC) kernel signature: 4db262e20e001154554aacba8ee069cf005e1d0d472bd35a6ff08601ed7ef2f2 run #0: crashed: INFO: task hung in proc_bulk run #1: crashed: INFO: task hung in proc_bulk run #2: crashed: INFO: task hung in proc_bulk run #3: crashed: INFO: task hung in proc_bulk run #4: crashed: INFO: task hung in proc_bulk run #5: crashed: INFO: task hung in proc_bulk run #6: OK run #7: OK run #8: OK run #9: OK testing release v5.3 testing commit 4d856f72c10ecb060868ed10ff1b1453943fc6c8 compiler: gcc version 8.4.1 20210217 (GCC) kernel signature: 8a03cb69477372e7c3f6c0fee23e5ea1b68880d5ca37439f59113cf3c4eda96e run #0: crashed: INFO: task hung in usb_bulk_msg run #1: crashed: INFO: task hung in usb_bulk_msg run #2: crashed: INFO: task hung in usb_bulk_msg run #3: crashed: INFO: task hung in usb_bulk_msg run #4: OK run #5: OK run #6: OK run #7: OK run #8: OK run #9: OK reproducer seems to be flaky testing release v5.2 testing commit 0ecfebd2b52404ae0c54a878c872bb93363ada36 compiler: gcc version 8.4.1 20210217 (GCC) kernel signature: a63def1637c68d4b2393eca6fa64f291c241df7444f98d045fce92c45e3140a6 run #0: crashed: INFO: task hung in usb_bulk_msg run #1: crashed: INFO: task hung in usb_bulk_msg run #2: crashed: INFO: task hung in usb_bulk_msg run #3: crashed: INFO: task hung in usb_bulk_msg run #4: crashed: INFO: task hung in usb_bulk_msg run #5: crashed: INFO: task hung in usb_bulk_msg run #6: crashed: INFO: task hung in usb_bulk_msg run #7: OK run #8: OK run #9: OK run #10: OK run #11: OK run #12: OK run #13: OK run #14: OK run #15: OK run #16: OK run #17: OK run #18: OK run #19: OK testing release v5.1 testing commit e93c9c99a629c61837d5a7fc2120cd2b6c70dbdd compiler: gcc version 8.4.1 20210217 (GCC) kernel signature: f8efdfe78b77cd25d04aab4225a16b81c92c36c009eef26f6201701b40898542 run #0: crashed: INFO: task hung in usb_bulk_msg run #1: crashed: INFO: task hung in usb_bulk_msg run #2: crashed: INFO: task hung in usb_bulk_msg run #3: crashed: INFO: task hung in usb_bulk_msg run #4: crashed: INFO: task hung in usb_bulk_msg run #5: crashed: INFO: task hung in usb_bulk_msg run #6: crashed: INFO: task hung in usb_bulk_msg run #7: crashed: INFO: task hung in usb_bulk_msg run #8: crashed: INFO: task hung in usb_bulk_msg run #9: crashed: INFO: task hung in usb_bulk_msg run #10: crashed: INFO: task hung in usb_bulk_msg run #11: crashed: INFO: task hung in usb_bulk_msg run #12: OK run #13: OK run #14: OK run #15: OK run #16: OK run #17: OK run #18: OK run #19: OK testing release v5.0 testing commit 1c163f4c7b3f621efff9b28a47abb36f7378d783 compiler: gcc version 8.4.1 20210217 (GCC) kernel signature: 8febb2553a8c0a5b6ddbcecc9d82d1b651fdece6c7b63653a085e30edb3aa2ec run #0: crashed: INFO: task hung in usb_bulk_msg run #1: crashed: INFO: task hung in usb_bulk_msg run #2: crashed: INFO: task hung in usb_bulk_msg run #3: crashed: INFO: task hung in usb_bulk_msg run #4: crashed: INFO: task hung in usb_bulk_msg run #5: crashed: INFO: task hung in usb_bulk_msg run #6: crashed: INFO: task hung in usb_bulk_msg run #7: crashed: INFO: task hung in usb_bulk_msg run #8: OK run #9: OK run #10: OK run #11: OK run #12: OK run #13: OK run #14: OK run #15: OK run #16: OK run #17: OK run #18: OK run #19: OK testing release v4.20 testing commit 8fe28cb58bcb235034b64cbbb7550a8a43fd88be compiler: gcc version 8.4.1 20210217 (GCC) kernel signature: e81a6fab327373d0bf545e9e00bd167f0ce0b5d26172c25cd8bfee3a0f5aa311 run #0: crashed: INFO: task hung in usb_bulk_msg run #1: crashed: INFO: task hung in usb_bulk_msg run #2: crashed: INFO: task hung in usb_bulk_msg run #3: crashed: INFO: task hung in usb_bulk_msg run #4: crashed: INFO: task hung in usb_bulk_msg run #5: crashed: INFO: task hung in usb_bulk_msg run #6: crashed: INFO: task hung in usb_bulk_msg run #7: crashed: INFO: task hung in usb_bulk_msg run #8: crashed: INFO: task hung in usb_bulk_msg run #9: crashed: INFO: task hung in usb_bulk_msg run #10: OK run #11: OK run #12: OK run #13: OK run #14: OK run #15: OK run #16: OK run #17: OK run #18: OK run #19: OK testing release v4.19 testing commit 84df9525b0c27f3ebc2ebb1864fa62a97fdedb7d compiler: gcc version 8.4.1 20210217 (GCC) kernel signature: 9bef6b32bcdf33de313a132c349c77e8ade5de2a1734e769b4455084d243971d run #0: crashed: INFO: task hung in usb_bulk_msg run #1: crashed: INFO: task hung in usb_bulk_msg run #2: crashed: INFO: task hung in usb_bulk_msg run #3: crashed: INFO: task hung in usb_bulk_msg run #4: OK run #5: OK run #6: OK run #7: OK run #8: OK run #9: OK run #10: OK run #11: OK run #12: OK run #13: OK run #14: OK run #15: OK run #16: OK run #17: OK run #18: OK run #19: boot failed: KASAN: use-after-free Read in dd_has_work testing release v4.18 testing commit 94710cac0ef4ee177a63b5227664b38c95bbf703 compiler: gcc version 8.4.1 20210217 (GCC) kernel signature: fcf0e0d27338d5d235ba0effab203d2fb83143b85586bc1cf4dc37344d1705e1 run #0: crashed: INFO: task hung in usb_bulk_msg run #1: crashed: INFO: task hung in usb_bulk_msg run #2: crashed: INFO: task hung in usb_bulk_msg run #3: crashed: INFO: task hung in usb_bulk_msg run #4: crashed: INFO: task hung in usb_bulk_msg run #5: crashed: INFO: task hung in usb_bulk_msg run #6: crashed: INFO: task hung in usb_bulk_msg run #7: crashed: INFO: task hung in usb_bulk_msg run #8: crashed: INFO: task hung in usb_bulk_msg run #9: crashed: INFO: task hung in usb_bulk_msg run #10: crashed: INFO: task hung in usb_bulk_msg run #11: crashed: INFO: task hung in usb_bulk_msg run #12: OK run #13: OK run #14: OK run #15: OK run #16: OK run #17: OK run #18: OK run #19: OK testing release v4.17 testing commit 29dcea88779c856c7dc92040a0c01233263101d4 failed to run ["make" "-j" "64" "ARCH=x86_64" "CC=/syzkaller/shared/bisect_bin/gcc-8.1.0/bin/gcc" "bzImage"]: exit status 2 testing release v4.16 testing commit 0adb32858b0bddf4ada5f364a84ed60b196dbcda orc_dump.c:106:2: error: 'elf_getshnum' is deprecated [-Werror=deprecated-declarations] orc_dump.c:111:2: error: 'elf_getshstrndx' is deprecated [-Werror=deprecated-declarations] elf.c:135:2: error: 'elf_getshnum' is deprecated [-Werror=deprecated-declarations] elf.c:140:2: error: 'elf_getshstrndx' is deprecated [-Werror=deprecated-declarations] testing release v4.15 testing commit d8a5b80568a9cb66810e75b182018e9edb68e8ff orc_dump.c:106:2: error: 'elf_getshnum' is deprecated [-Werror=deprecated-declarations] orc_dump.c:111:2: error: 'elf_getshstrndx' is deprecated [-Werror=deprecated-declarations] pager.c:36:12: error: passing argument 2 to 'restrict'-qualified parameter aliases with argument 4 [-Werror=restrict] elf.c:135:2: error: 'elf_getshnum' is deprecated [-Werror=deprecated-declarations] elf.c:140:2: error: 'elf_getshstrndx' is deprecated [-Werror=deprecated-declarations] testing release v4.14 testing commit bebc6082da0a9f5d47a1ea2edc099bf671058bd4 orc_dump.c:105:2: error: 'elf_getshnum' is deprecated [-Werror=deprecated-declarations] orc_dump.c:110:2: error: 'elf_getshstrndx' is deprecated [-Werror=deprecated-declarations] elf.c:134:2: error: 'elf_getshnum' is deprecated [-Werror=deprecated-declarations] elf.c:139:2: error: 'elf_getshstrndx' is deprecated [-Werror=deprecated-declarations] pager.c:36:12: error: passing argument 2 to 'restrict'-qualified parameter aliases with argument 4 [-Werror=restrict] testing release v4.13 testing commit 569dbb88e80deb68974ef6fdd6a13edb9d686261 pager.c:35:12: error: passing argument 2 to 'restrict'-qualified parameter aliases with argument 4 [-Werror=restrict] elf.c:144:2: error: 'elf_getshnum' is deprecated [-Werror=deprecated-declarations] elf.c:149:2: error: 'elf_getshstrndx' is deprecated [-Werror=deprecated-declarations] testing release v4.12 testing commit 6f7da290413ba713f0cdd9ff1a2a9bb129ef4f6c pager.c:35:12: error: passing argument 2 to 'restrict'-qualified parameter aliases with argument 4 [-Werror=restrict] elf.c:141:2: error: 'elf_getshnum' is deprecated [-Werror=deprecated-declarations] elf.c:146:2: error: 'elf_getshstrndx' is deprecated [-Werror=deprecated-declarations] testing release v4.11 testing commit a351e9b9fc24e982ec2f0e76379a49826036da12 elf.c:141:2: error: 'elf_getshnum' is deprecated [-Werror=deprecated-declarations] elf.c:146:2: error: 'elf_getshstrndx' is deprecated [-Werror=deprecated-declarations] pager.c:35:12: error: passing argument 2 to 'restrict'-qualified parameter aliases with argument 4 [-Werror=restrict] testing release v4.10 testing commit c470abd4fde40ea6a0846a2beab642a578c0b8cd tools/include/linux/log2.h:19:1: error: ignoring attribute 'noreturn' because it conflicts with attribute 'const' [-Werror=attributes] elf.c:129:2: error: 'elf_getshnum' is deprecated [-Werror=deprecated-declarations] elf.c:134:2: error: 'elf_getshstrndx' is deprecated [-Werror=deprecated-declarations] pager.c:35:12: error: passing argument 2 to 'restrict'-qualified parameter aliases with argument 4 [-Werror=restrict] testing release v4.9 testing commit 69973b830859bc6529a7a0468ba0d80ee5117826 tools/include/linux/log2.h:19:1: error: ignoring attribute 'noreturn' because it conflicts with attribute 'const' [-Werror=attributes] elf.c:129:2: error: 'elf_getshnum' is deprecated [-Werror=deprecated-declarations] elf.c:134:2: error: 'elf_getshstrndx' is deprecated [-Werror=deprecated-declarations] pager.c:35:12: error: passing argument 2 to 'restrict'-qualified parameter aliases with argument 4 [-Werror=restrict] testing release v4.8 testing commit c8d2bc9bc39ebea8437fd974fdbc21847bb897a3 tools/include/linux/log2.h:19:1: error: ignoring attribute 'noreturn' because it conflicts with attribute 'const' [-Werror=attributes] elf.c:129:2: error: 'elf_getshnum' is deprecated [-Werror=deprecated-declarations] elf.c:134:2: error: 'elf_getshstrndx' is deprecated [-Werror=deprecated-declarations] pager.c:33:12: error: passing argument 2 to 'restrict'-qualified parameter aliases with argument 4 [-Werror=restrict] testing release v4.7 testing commit 523d939ef98fd712632d93a5a2b588e477a7565e tools/include/linux/log2.h:19:1: error: ignoring attribute 'noreturn' because it conflicts with attribute 'const' [-Werror=attributes] elf.c:122:2: error: 'elf_getshnum' is deprecated [-Werror=deprecated-declarations] elf.c:127:2: error: 'elf_getshstrndx' is deprecated [-Werror=deprecated-declarations] pager.c:33:12: error: passing argument 2 to 'restrict'-qualified parameter aliases with argument 4 [-Werror=restrict] testing release v4.6 testing commit 2dcd0af568b0cf583645c8a317dd12e344b1c72a tools/include/linux/log2.h:19:1: error: ignoring attribute 'noreturn' because it conflicts with attribute 'const' [-Werror=attributes] pager.c:33:12: error: passing argument 2 to 'restrict'-qualified parameter aliases with argument 4 [-Werror=restrict] Reproducer flagged being flaky revisions tested: 18, total time: 4h50m13.003685359s (build: 2h2m55.588656994s, test: 2h41m38.500222134s) the crash already happened on the oldest tested release commit msg: Linux 4.18 crash: INFO: task hung in usb_bulk_msg Bluetooth: hci5: command 0x0406 tx timeout NOHZ: local_softirq_pending 08 NOHZ: local_softirq_pending 08 NOHZ: local_softirq_pending 08 NOHZ: local_softirq_pending 08 INFO: task syz-executor.0:10173 blocked for more than 140 seconds. Not tainted 4.18.0-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.0 D28520 10173 8568 0x00080004 Call Trace: context_switch kernel/sched/core.c:2853 [inline] __schedule+0x80c/0x1fc0 kernel/sched/core.c:3501 schedule+0x7f/0x1b0 kernel/sched/core.c:3545 schedule_timeout+0x70e/0xd20 kernel/time/timer.c:1777 do_wait_for_common kernel/sched/completion.c:83 [inline] __wait_for_common kernel/sched/completion.c:104 [inline] wait_for_common+0x3fb/0x5d0 kernel/sched/completion.c:115 wait_for_completion_timeout+0xe/0x10 kernel/sched/completion.c:155 usb_start_wait_urb+0x12a/0x500 drivers/usb/core/message.c:62 usb_bulk_msg+0x1d4/0x610 drivers/usb/core/message.c:253 proc_bulk+0x4ed/0x640 drivers/usb/core/devio.c:1192 usbdev_do_ioctl+0x1133/0x27a0 drivers/usb/core/devio.c:2400 usbdev_ioctl+0x9/0x10 drivers/usb/core/devio.c:2550 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:500 [inline] do_vfs_ioctl+0x196/0x1050 fs/ioctl.c:684 ksys_ioctl+0x62/0x90 fs/ioctl.c:701 __do_sys_ioctl fs/ioctl.c:708 [inline] __se_sys_ioctl fs/ioctl.c:706 [inline] __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:706 do_syscall_64+0xda/0x540 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x4665e9 Code: 00 84 c9 0f 85 f1 fd ff ff 83 3d 41 05 3a 01 00 0f 85 c2 00 00 00 48 8d 0d a4 2e 43 00 48 89 88 a8 00 00 00 0f 57 c0 0f 11 84 <24> 90 00 00 00 48 8b 0d d3 df 36 01 48 89 8c 24 90 00 00 00 48 8d RSP: 002b:00007f8d54c0c188 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 000000000056bf80 RCX: 00000000004665e9 RDX: 0000000020000340 RSI: 00000000c0185502 RDI: 0000000000000004 RBP: 00000000004bfcc4 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf80 R13: 00007fffbdb1458f R14: 00007f8d54c0c300 R15: 0000000000022000 Showing all locks held in the system: 1 lock held by khungtaskd/1500: #0: 00000000d66e162d (rcu_read_lock){....}, at: debug_show_all_locks+0x5b/0x27a kernel/locking/lockdep.c:4461 2 locks held by in:imklog/7864: #0: 000000007ed0f8bc (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xa7/0xd0 fs/file.c:766 #1: 00000000b35d2fef (logbuf_lock){....}, at: is_bpf_text_address+0x0/0xe0 kernel/bpf/core.c:530 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 1500 Comm: khungtaskd Not tainted 4.18.0-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x15a/0x20d lib/dump_stack.c:113 nmi_cpu_backtrace.cold.0+0x13/0xb6 lib/nmi_backtrace.c:103 nmi_trigger_cpumask_backtrace+0xf6/0x11a lib/nmi_backtrace.c:62 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38 trigger_all_cpu_backtrace include/linux/nmi.h:138 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:196 [inline] watchdog+0x512/0x940 kernel/hung_task.c:252 kthread+0x316/0x3d0 kernel/kthread.c:246 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:412 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 skipped: idling at native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:54