From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: <35VbTWgkbALwu01mcnngtcrrkf.iqqingwugteqpvgpv.eqo@M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com> ARC-Seal: i=1; a=rsa-sha256; t=1523799781; cv=none; d=google.com; s=arc-20160816; b=Ktxhags6dEshZaTt+huSrW6OrbrMiJfNCHYKdU68uV3jcx+k/OiW+ybFs3LtkQwa44 cLQenK631S0ms4DwGmxD80fiqwdw+HiVw83mW6qArxtsno+ETqs7WUd0GRA3qHHVQbgp Wa9QVX/iPjuICIzXexEi3Qrhig1SFVuMPsAVDFCrfZXD2wDQcKEbTvuryw/vlG8OkTsq S/3bwCwQ6tmcs3yvXv+8sdEtiwIkpQ4L/4eMcPoyfTxXV2Z2dvIh4k+GgwOcJ0JXj3be j7865cviIegEIwQTM3e7qWTAig+GHAveoPte43B/vkxS/SA6sIkmp8KythPOLJ+9TNkx E8Iw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=to:from:subject:message-id:in-reply-to:date:mime-version :arc-authentication-results; bh=P00I2/dHXuR5WgrVN7YYTtLuxb6gJF5iDJwcJ9L+b1o=; b=hT2ANb0QXyL2q3Aw9zYXEj/+A0Pw0pSj2djWkgCGGxkc5RkOT+JoxQeIaeq5syPdbJ V1ZM1X80ZTawoXSNQpuwbHo1r2IAOHQZEHFi3EhmKC+OdUaQCzANM9LsoLPbIvLq7E26 cDQwxqEJR8+yiyiqBe5t38soA1Sm8pyprGmxYwaVVsckRYB1HQFszhRVihRvz77BVQ1z lQ4nMHl1uSb0eVYJ9Es6wkoTHYA9tSojGr7Yrbk5SPimTWBA88Z/5zYt1+EB1iARHEpS p/shdY/LqaGx+NE789MqL1i3jc6ArBcNprhpH6Ym5FYqqfRxu6oJ3aV4fvApHnlD89JV pNRQ== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of 35vbtwgkbalwu01mcnngtcrrkf.iqqingwugteqpvgpv.eqo@m3kw2wvrgufz5godrsrytgd7.apphosting.bounces.google.com designates 209.85.220.69 as permitted sender) smtp.mailfrom=35VbTWgkbALwu01mcnngtcrrkf.iqqingwugteqpvgpv.eqo@M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=appspotmail.com Authentication-Results: mx.google.com; spf=pass (google.com: domain of 35vbtwgkbalwu01mcnngtcrrkf.iqqingwugteqpvgpv.eqo@m3kw2wvrgufz5godrsrytgd7.apphosting.bounces.google.com designates 209.85.220.69 as permitted sender) smtp.mailfrom=35VbTWgkbALwu01mcnngtcrrkf.iqqingwugteqpvgpv.eqo@M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=appspotmail.com X-Google-Smtp-Source: AIpwx4/051ns7uKBWG6fxK1+X8HIUWf1Y3HNKhzDnsXQxDE9kPI2S+IxYL38YmNtwDbMtpKM/5QwdeFuLUNzeLX20GFH6F+aA8wB MIME-Version: 1.0 Date: Sun, 15 Apr 2018 06:43:01 -0700 In-Reply-To: <883d24f7d4ccc52e19056928c5be@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <001a113f8d5cab39bd0569e3482a@google.com> Subject: Re: INFO: rcu detected stall in n_tty_receive_char_special From: syzbot To: dvyukov@google.com, gregkh@linuxfoundation.org, jslaby@suse.com, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8"; format=flowed; delsp=yes X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1596979907220664835?= X-GMAIL-MSGID: =?utf-8?q?1597819879782516813?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: syzbot has found reproducer for the following crash on upstream commit 18b7fd1c93e5204355ddbf2608a097d64df81b88 (Sat Apr 14 15:50:50 2018 +0000) Merge branch 'akpm' (patches from Andrew) syzbot dashboard link: https://syzkaller.appspot.com/bug?extid=18df353d7540aa6b5467 So far this crash happened 2 times on upstream. C reproducer: https://syzkaller.appspot.com/x/repro.c?id=5283196245639168 syzkaller reproducer: https://syzkaller.appspot.com/x/repro.syz?id=5978502260064256 Raw console output: https://syzkaller.appspot.com/x/log.txt?id=4993708470566912 Kernel config: https://syzkaller.appspot.com/x/.config?id=-8852471259444315113 compiler: gcc (GCC) 8.0.1 20180413 (experimental) IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+18df353d7540aa6b5467@syzkaller.appspotmail.com It will help syzbot understand when the bug is fixed. INFO: rcu_sched self-detected stall on CPU 1-....: (124999 ticks this GP) idle=792/1/4611686018427387906 softirq=9920/9920 fqs=31243 (t=125000 jiffies g=4830 c=4829 q=20) NMI backtrace for cpu 1 CPU: 1 PID: 4467 Comm: syzkaller756606 Not tainted 4.16.0+ #3 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+0x1b9/0x294 lib/dump_stack.c:113 nmi_cpu_backtrace.cold.4+0x19/0xce lib/nmi_backtrace.c:103 nmi_trigger_cpumask_backtrace+0x151/0x192 lib/nmi_backtrace.c:62 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38 trigger_single_cpu_backtrace include/linux/nmi.h:156 [inline] rcu_dump_cpu_stacks+0x175/0x1c2 kernel/rcu/tree.c:1376 print_cpu_stall kernel/rcu/tree.c:1525 [inline] check_cpu_stall.isra.61.cold.80+0x36c/0x59a kernel/rcu/tree.c:1593 __rcu_pending kernel/rcu/tree.c:3356 [inline] rcu_pending kernel/rcu/tree.c:3401 [inline] rcu_check_callbacks+0x21b/0xad0 kernel/rcu/tree.c:2763 update_process_times+0x2d/0x70 kernel/time/timer.c:1636 tick_sched_handle+0x9f/0x180 kernel/time/tick-sched.c:173 tick_sched_timer+0x45/0x130 kernel/time/tick-sched.c:1283 __run_hrtimer kernel/time/hrtimer.c:1386 [inline] __hrtimer_run_queues+0x3e3/0x10a0 kernel/time/hrtimer.c:1448 hrtimer_interrupt+0x286/0x650 kernel/time/hrtimer.c:1506 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1025 [inline] smp_apic_timer_interrupt+0x15d/0x710 arch/x86/kernel/apic/apic.c:1050 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:862 RIP: 0010:echo_char+0x96/0x2e0 drivers/tty/n_tty.c:915 RSP: 0018:ffff8801b079f6f8 EFLAGS: 00000293 ORIG_RAX: ffffffffffffff13 RAX: ffff8801b06ee1c0 RBX: ffffc90001e64000 RCX: ffffffff837ab4a7 RDX: 0000000000000000 RSI: ffffffff837ab4b6 RDI: 0000000000000001 RBP: ffff8801b079f728 R08: ffff8801b06ee1c0 R09: 0000000000000001 R10: ffff8801b06eea20 R11: ffff8801b06ee1c0 R12: 000000000000000f R13: ffff8801b02b0dc0 R14: 000000012b1bcc47 R15: 0000000000000c47 n_tty_receive_char_special+0x13b3/0x31c0 drivers/tty/n_tty.c:1306 n_tty_receive_buf_fast drivers/tty/n_tty.c:1577 [inline] __receive_buf drivers/tty/n_tty.c:1611 [inline] n_tty_receive_buf_common+0x20ca/0x2c50 drivers/tty/n_tty.c:1709 n_tty_receive_buf+0x30/0x40 drivers/tty/n_tty.c:1738 tiocsti drivers/tty/tty_io.c:2171 [inline] tty_ioctl+0x7e7/0x1870 drivers/tty/tty_io.c:2557 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:500 [inline] do_vfs_ioctl+0x1cf/0x16a0 fs/ioctl.c:684 ksys_ioctl+0xa9/0xd0 fs/ioctl.c:701 SYSC_ioctl fs/ioctl.c:708 [inline] SyS_ioctl+0x24/0x30 fs/ioctl.c:706 do_syscall_64+0x29e/0x9d0 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x4404b9 RSP: 002b:00007ffee94bd7f8 EFLAGS: 00000213 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00000000200006c0 RCX: 00000000004404b9 RDX: 00000000200000c0 RSI: 0000000000005412 RDI: 0000000000000012 RBP: 6d74702f7665642f R08: 000000000000000a R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000213 R12: 0000000000401c30 R13: 0000000000401cc0 R14: 0000000000000000 R15: 0000000000000000