On Tue, Jun 26, 2018 at 3:49 AM, Sergey Senozhatsky <sergey.senozhatsky.work@xxxxxxxxx> wrote: > On (06/25/18 16:19), syzbot wrote: >> Hello, >> >> syzbot found the following crash on: >> >> HEAD commit: 77072ca59fdd Merge tag 'for-linus-20180623' of git://git.k.. >> git tree: upstream >> console output: https://syzkaller.appspot.com/x/log.txt?x=169c7c04400000 >> kernel config: https://syzkaller.appspot.com/x/.config?x=befbcd7305e41bb0 >> dashboard link: https://syzkaller.appspot.com/bug?extid=d29d18215e477cfbfbdd >> compiler: gcc (GCC) 8.0.1 20180413 (experimental) >> syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=1585147f800000 >> >> IMPORTANT: if you fix the bug, please add the following tag to the commit: >> Reported-by: syzbot+d29d18215e477cfbfbdd@xxxxxxxxxxxxxxxxxxxxxxxxx >> >> llcp: nfc_llcp_send_ui_frame: Could not allocate PDU >> llcp: nfc_llcp_send_ui_frame: Could not allocate PDU >> llcp: nfc_llcp_send_ui_frame: Could not allocate PDU >> llcp: nfc_llcp_send_ui_frame: Could not allocate PDU >> llcp: nfc_llcp_send_ui_frame: Could not allocate PDU > > Hi, > > Thanks for the report. > > I'll Cc networking people on this. > > I've a strong feeling that we saw it before. A very similar bug was reported before: https://groups.google.com/d/msg/syzkaller-bugs/Axw2t6DvU60/TfLUoXsjBAAJ > The kernel is > CONFIG_PREEMPT_VOLUNTARY=y, llcp_sock_sendmsg() stuck in a error > reporting loop: > > do { > ... > pdu = nfc_alloc_send_skb(sock->dev, &sock->sk, MSG_DONTWAIT, > frag_len + LLCP_HEADER_SIZE, &err); > if (pdu == NULL) { > pr_err("Could not allocate PDU\n"); > continue; > } > ... > } while (remaining_len > 0); > > [ 1004.674843] llcp: nfc_llcp_send_ui_frame: Could not allocate PDU > [ 1004.681035] llcp: nfc_llcp_send_ui_frame: Could not allocate PDU > ... > [ 1098.508526] llcp: nfc_llcp_send_ui_frame: Could not allocate PDU > [ 1098.514698] llcp: nfc_llcp_send_ui_frame: Could not allocate PDU > [ 1098.520844] INFO: rcu_sched self-detected stall on CPU > > 94 seconds worth of heavy printing, no preemption: > >> INFO: rcu_sched self-detected stall on CPU >> 1-....: (20918 ticks this GP) idle=55a/1/4611686018427387906 >> softirq=11347/11347 fqs=20240 >> (t=125005 jiffies g=5572 c=5571 q=149) >> NMI backtrace for cpu 1 >> CPU: 1 PID: 4811 Comm: syz-executor0 Not tainted 4.18.0-rc1+ #115 >> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS >> Google 01/01/2011 >> Call Trace: >> <IRQ> >> __dump_stack lib/dump_stack.c:77 [inline] >> dump_stack+0x1c9/0x2b4 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:1336 >> print_cpu_stall kernel/rcu/tree.c:1485 [inline] >> check_cpu_stall.isra.60.cold.78+0x36c/0x5a6 kernel/rcu/tree.c:1553 >> __rcu_pending kernel/rcu/tree.c:3244 [inline] >> rcu_pending kernel/rcu/tree.c:3291 [inline] >> rcu_check_callbacks+0x23f/0xcd0 kernel/rcu/tree.c:2646 >> update_process_times+0x2d/0x70 kernel/time/timer.c:1636 >> tick_sched_handle+0x9f/0x180 kernel/time/tick-sched.c:164 >> tick_sched_timer+0x45/0x130 kernel/time/tick-sched.c:1274 >> __run_hrtimer kernel/time/hrtimer.c:1398 [inline] >> __hrtimer_run_queues+0x3eb/0x10c0 kernel/time/hrtimer.c:1460 >> hrtimer_interrupt+0x2f3/0x750 kernel/time/hrtimer.c:1518 >> local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1025 [inline] >> smp_apic_timer_interrupt+0x165/0x730 arch/x86/kernel/apic/apic.c:1050 >> apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:863 >> </IRQ> >> RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:783 >> [inline] >> RIP: 0010:console_unlock+0xc84/0x10b0 kernel/printk/printk.c:2397 >> Code: c1 e8 03 42 80 3c 38 00 0f 85 bd 03 00 00 48 83 3d 38 f7 8e 07 00 0f >> 84 69 02 00 00 e8 45 56 19 00 48 8b bd b0 fe ff ff 57 9d <0f> 1f 44 00 00 e9 >> 96 f5 ff ff e8 2d 56 19 00 48 8b 7d 08 e8 94 cf >> RSP: 0018:ffff8801aab0f358 EFLAGS: 00000293 ORIG_RAX: ffffffffffffff13 >> RAX: ffff8801aa2802c0 RBX: 0000000000000200 RCX: 1ffff10035450163 >> RDX: 0000000000000000 RSI: ffffffff8162b8fb RDI: 0000000000000293 >> RBP: ffff8801aab0f4c0 R08: ffff8801aa280af8 R09: 0000000000000006 >> R10: ffff8801aa2802c0 R11: 0000000000000000 R12: 0000000000000000 >> R13: ffffffff84ea9880 R14: 0000000000000001 R15: dffffc0000000000 >> vprintk_emit+0x6c6/0xdf0 kernel/printk/printk.c:1907 >> vprintk_default+0x28/0x30 kernel/printk/printk.c:1948 >> vprintk_func+0x7a/0xe7 kernel/printk/printk_safe.c:382 >> printk+0xa7/0xcf kernel/printk/printk.c:1981 >> nfc_llcp_send_ui_frame.cold.9+0x18/0x1f net/nfc/llcp_commands.c:758 >> llcp_sock_sendmsg+0x278/0x350 net/nfc/llcp_sock.c:786 >> sock_sendmsg_nosec net/socket.c:645 [inline] >> sock_sendmsg+0xd5/0x120 net/socket.c:655 >> ___sys_sendmsg+0x51d/0x930 net/socket.c:2161 >> __sys_sendmmsg+0x240/0x6f0 net/socket.c:2256 >> __do_sys_sendmmsg net/socket.c:2285 [inline] >> __se_sys_sendmmsg net/socket.c:2282 [inline] >> __x64_sys_sendmmsg+0x9d/0x100 net/socket.c:2282 >> do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 >> entry_SYSCALL_64_after_hwframe+0x49/0xbe > > > So we can try switching to ratelimited error reporting > [that would be option A]: > > --- > > diff --git a/net/nfc/llcp_commands.c b/net/nfc/llcp_commands.c > index 2ceefa183cee..2f3becb709b8 100644 > --- a/net/nfc/llcp_commands.c > +++ b/net/nfc/llcp_commands.c > @@ -755,7 +755,7 @@ int nfc_llcp_send_ui_frame(struct nfc_llcp_sock *sock, u8 ssap, u8 dsap, > pdu = nfc_alloc_send_skb(sock->dev, &sock->sk, MSG_DONTWAIT, > frag_len + LLCP_HEADER_SIZE, &err); > if (pdu == NULL) { > - pr_err("Could not allocate PDU\n"); > + pr_err_ratelimited("Could not allocate PDU\n"); > continue; > } > > --- > > > Or ratelimited error reporting and cond_resched() > [that would be option B]: > > --- > > diff --git a/net/nfc/llcp_commands.c b/net/nfc/llcp_commands.c > index 2ceefa183cee..61741db4c4e6 100644 > --- a/net/nfc/llcp_commands.c > +++ b/net/nfc/llcp_commands.c > @@ -755,7 +755,8 @@ int nfc_llcp_send_ui_frame(struct nfc_llcp_sock *sock, u8 ssap, u8 dsap, > pdu = nfc_alloc_send_skb(sock->dev, &sock->sk, MSG_DONTWAIT, > frag_len + LLCP_HEADER_SIZE, &err); > if (pdu == NULL) { > - pr_err("Could not allocate PDU\n"); > + pr_err_ratelimited("Could not allocate PDU\n"); > + cond_resched(); > continue; > } > > --- > > -ss > > -- > You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group. > To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bugs+unsubscribe@xxxxxxxxxxxxxxxx. > To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/20180626014924.GB11229%40jagdpanzerIV. > For more options, visit https://groups.google.com/d/optout.
