Re: unregister_netdevice: waiting for DEV to become free (2)
From: Alexei Starovoitov
Date: Fri Oct 11 2019 - 11:12:24 EST
On Fri, Oct 11, 2019 at 3:15 AM Tetsuo Handa
<penguin-kernel@xxxxxxxxxxxxxxxxxxx> wrote:
>
> Hello.
>
> I noticed that syzbot is reporting that refcount incremented by bpf(BPF_MAP_UPDATE_ELEM)
> syscall is not decremented when unregister_netdevice() is called. Is this a BPF bug?
Jesper, Toke,
please take a look.
> Kernel: 9e208aa06c2109b45eec6be049a8e47034748c20 on linux.git
> Config: https://syzkaller.appspot.com/text?tag=KernelConfig&x=73c2aace7604ab7
> Reproducer: https://syzkaller.appspot.com/text?tag=ReproC&x=1215afaf600000
> Debug printk patch:
> ----------------------------------------
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index 9eda1c31d1f7..542a47fe6998 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -3732,10 +3732,7 @@ void netdev_run_todo(void);
> *
> * Release reference to device to allow it to be freed.
> */
> -static inline void dev_put(struct net_device *dev)
> -{
> - this_cpu_dec(*dev->pcpu_refcnt);
> -}
> +extern void dev_put(struct net_device *dev);
>
> /**
> * dev_hold - get reference to device
> @@ -3743,10 +3740,7 @@ static inline void dev_put(struct net_device *dev)
> *
> * Hold reference to device to keep it from being freed.
> */
> -static inline void dev_hold(struct net_device *dev)
> -{
> - this_cpu_inc(*dev->pcpu_refcnt);
> -}
> +extern void dev_hold(struct net_device *dev);
>
> /* Carrier loss detection, dial on demand. The functions netif_carrier_on
> * and _off may be called from IRQ context, but it is caller
> diff --git a/net/core/dev.c b/net/core/dev.c
> index bf3ed413abaf..21f82aa92fad 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -8968,8 +8968,8 @@ static void netdev_wait_allrefs(struct net_device *dev)
> refcnt = netdev_refcnt_read(dev);
>
> if (refcnt && time_after(jiffies, warning_time + 10 * HZ)) {
> - pr_emerg("unregister_netdevice: waiting for %s to become free. Usage count = %d\n",
> - dev->name, refcnt);
> + pr_emerg("unregister_netdevice: waiting for %s to become free. Usage count = %d %px\n",
> + dev->name, refcnt, dev);
> warning_time = jiffies;
> }
> }
> @@ -9930,3 +9930,24 @@ static int __init net_dev_init(void)
> }
>
> subsys_initcall(net_dev_init);
> +
> +
> +void dev_put(struct net_device *dev)
> +{
> + this_cpu_dec(*dev->pcpu_refcnt);
> + if (!strcmp(dev->name, "bridge_slave_0")) {
> + printk("dev_put: %px %d", dev, netdev_refcnt_read(dev));
> + dump_stack();
> + }
> +}
> +EXPORT_SYMBOL(dev_put);
> +
> +void dev_hold(struct net_device *dev)
> +{
> + if (!strcmp(dev->name, "bridge_slave_0")) {
> + printk("dev_hold: %px %d", dev, netdev_refcnt_read(dev));
> + dump_stack();
> + }
> + this_cpu_inc(*dev->pcpu_refcnt);
> +}
> +EXPORT_SYMBOL(dev_hold);
> ----------------------------------------
>
> ----------------------------------------
> Oct 11 14:33:06 ubuntu kernel: [ 114.251175][ T8866] dev_hold: ffff888091fd2000 100
> Oct 11 14:33:06 ubuntu kernel: [ 114.251185][ T8866] CPU: 3 PID: 8866 Comm: a.out Not tainted 5.4.0-rc2+ #217
> Oct 11 14:33:06 ubuntu kernel: [ 114.251199][ T8866] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 04/13/2018
> Oct 11 14:33:06 ubuntu kernel: [ 114.251208][ T8866] Call Trace:
> Oct 11 14:33:06 ubuntu kernel: [ 114.251232][ T8866] dump_stack+0x154/0x1c5
> Oct 11 14:33:06 ubuntu kernel: [ 114.251253][ T8866] dev_hold+0x73/0x80
> Oct 11 14:33:06 ubuntu kernel: [ 114.251267][ T8866] dev_get_by_index+0x1b3/0x2d0
> Oct 11 14:33:06 ubuntu kernel: [ 114.251280][ T8866] __dev_map_alloc_node+0x1c7/0x360
> Oct 11 14:33:06 ubuntu kernel: [ 114.251299][ T8866] dev_map_hash_update_elem+0x485/0x670
> Oct 11 14:33:06 ubuntu kernel: [ 114.251320][ T8866] __do_sys_bpf+0x35d6/0x38c0
> Oct 11 14:33:06 ubuntu kernel: [ 114.251337][ T8866] ? bpf_prog_load+0x1470/0x1470
> Oct 11 14:33:06 ubuntu kernel: [ 114.251351][ T8866] ? do_wp_page+0x3c8/0x1310
> Oct 11 14:33:06 ubuntu kernel: [ 114.251364][ T8866] ? finish_mkwrite_fault+0x300/0x300
> Oct 11 14:33:06 ubuntu kernel: [ 114.251381][ T8866] ? find_held_lock+0x35/0x1e0
> Oct 11 14:33:06 ubuntu kernel: [ 114.251397][ T8866] ? __do_page_fault+0x504/0xb60
> Oct 11 14:33:06 ubuntu kernel: [ 114.251413][ T8866] ? lock_downgrade+0x900/0x900
> Oct 11 14:33:06 ubuntu kernel: [ 114.251426][ T8866] ? __pmd_alloc+0x410/0x410
> Oct 11 14:33:06 ubuntu kernel: [ 114.251446][ T8866] ? __kasan_check_write+0x14/0x20
> Oct 11 14:33:06 ubuntu kernel: [ 114.251457][ T8866] ? up_read+0x1b6/0x7a0
> Oct 11 14:33:06 ubuntu kernel: [ 114.251471][ T8866] ? down_read_nested+0x480/0x480
> Oct 11 14:33:06 ubuntu kernel: [ 114.251494][ T8866] ? do_syscall_64+0x26/0x6a0
> Oct 11 14:33:06 ubuntu kernel: [ 114.251507][ T8866] ? entry_SYSCALL_64_after_hwframe+0x49/0xbe
> Oct 11 14:33:06 ubuntu kernel: [ 114.251515][ T8866] ? do_syscall_64+0x26/0x6a0
> Oct 11 14:33:06 ubuntu kernel: [ 114.251528][ T8866] __x64_sys_bpf+0x73/0xb0
> Oct 11 14:33:06 ubuntu kernel: [ 114.251541][ T8866] do_syscall_64+0xde/0x6a0
> Oct 11 14:33:06 ubuntu kernel: [ 114.251559][ T8866] entry_SYSCALL_64_after_hwframe+0x49/0xbe
> (...snipped...)
> Oct 11 14:33:10 ubuntu kernel: [ 117.459637][ T9584] dev_hold: ffff888091fd2000 200
> Oct 11 14:33:10 ubuntu kernel: [ 117.459644][ T9584] CPU: 4 PID: 9584 Comm: a.out Not tainted 5.4.0-rc2+ #217
> Oct 11 14:33:10 ubuntu kernel: [ 117.459652][ T9584] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 04/13/2018
> Oct 11 14:33:10 ubuntu kernel: [ 117.459656][ T9584] Call Trace:
> Oct 11 14:33:10 ubuntu kernel: [ 117.459669][ T9584] dump_stack+0x154/0x1c5
> Oct 11 14:33:10 ubuntu kernel: [ 117.459682][ T9584] dev_hold+0x73/0x80
> Oct 11 14:33:10 ubuntu kernel: [ 117.459695][ T9584] dev_get_by_index+0x1b3/0x2d0
> Oct 11 14:33:10 ubuntu kernel: [ 117.459706][ T9584] __dev_map_alloc_node+0x1c7/0x360
> Oct 11 14:33:10 ubuntu kernel: [ 117.459720][ T9584] dev_map_hash_update_elem+0x485/0x670
> Oct 11 14:33:10 ubuntu kernel: [ 117.459749][ T9584] __do_sys_bpf+0x35d6/0x38c0
> Oct 11 14:33:10 ubuntu kernel: [ 117.459762][ T9584] ? bpf_prog_load+0x1470/0x1470
> Oct 11 14:33:10 ubuntu kernel: [ 117.459769][ T9584] ? do_wp_page+0x3c8/0x1310
> Oct 11 14:33:10 ubuntu kernel: [ 117.459778][ T9584] ? finish_mkwrite_fault+0x300/0x300
> Oct 11 14:33:10 ubuntu kernel: [ 117.459787][ T9584] ? find_held_lock+0x35/0x1e0
> Oct 11 14:33:10 ubuntu kernel: [ 117.459797][ T9584] ? __do_page_fault+0x504/0xb60
> Oct 11 14:33:10 ubuntu kernel: [ 117.459807][ T9584] ? lock_downgrade+0x900/0x900
> Oct 11 14:33:10 ubuntu kernel: [ 117.459814][ T9584] ? __pmd_alloc+0x410/0x410
> Oct 11 14:33:10 ubuntu kernel: [ 117.459828][ T9584] ? __kasan_check_write+0x14/0x20
> Oct 11 14:33:10 ubuntu kernel: [ 117.459835][ T9584] ? up_read+0x1b6/0x7a0
> Oct 11 14:33:10 ubuntu kernel: [ 117.459846][ T9584] ? down_read_nested+0x480/0x480
> Oct 11 14:33:10 ubuntu kernel: [ 117.459862][ T9584] ? do_syscall_64+0x26/0x6a0
> Oct 11 14:33:10 ubuntu kernel: [ 117.459871][ T9584] ? entry_SYSCALL_64_after_hwframe+0x49/0xbe
> Oct 11 14:33:10 ubuntu kernel: [ 117.459878][ T9584] ? do_syscall_64+0x26/0x6a0
> Oct 11 14:33:10 ubuntu kernel: [ 117.459891][ T9584] __x64_sys_bpf+0x73/0xb0
> Oct 11 14:33:10 ubuntu kernel: [ 117.459901][ T9584] do_syscall_64+0xde/0x6a0
> Oct 11 14:33:10 ubuntu kernel: [ 117.459911][ T9584] entry_SYSCALL_64_after_hwframe+0x49/0xbe
> (...snipped...)
> Oct 11 14:33:26 ubuntu kernel: [ 134.146838][T13860] dev_hold: ffff888091fd2000 850
> Oct 11 14:33:26 ubuntu kernel: [ 134.146847][T13860] CPU: 4 PID: 13860 Comm: a.out Not tainted 5.4.0-rc2+ #217
> Oct 11 14:33:26 ubuntu kernel: [ 134.146853][T13860] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 04/13/2018
> Oct 11 14:33:26 ubuntu kernel: [ 134.146859][T13860] Call Trace:
> Oct 11 14:33:26 ubuntu kernel: [ 134.146872][T13860] dump_stack+0x154/0x1c5
> Oct 11 14:33:26 ubuntu kernel: [ 134.146885][T13860] dev_hold+0x73/0x80
> Oct 11 14:33:26 ubuntu kernel: [ 134.146893][T13860] dev_get_by_index+0x1b3/0x2d0
> Oct 11 14:33:26 ubuntu kernel: [ 134.146903][T13860] __dev_map_alloc_node+0x1c7/0x360
> Oct 11 14:33:26 ubuntu kernel: [ 134.146918][T13860] dev_map_hash_update_elem+0x485/0x670
> Oct 11 14:33:26 ubuntu kernel: [ 134.146932][T13860] __do_sys_bpf+0x35d6/0x38c0
> Oct 11 14:33:26 ubuntu kernel: [ 134.146944][T13860] ? bpf_prog_load+0x1470/0x1470
> Oct 11 14:33:26 ubuntu kernel: [ 134.146953][T13860] ? do_wp_page+0x3c8/0x1310
> Oct 11 14:33:26 ubuntu kernel: [ 134.146964][T13860] ? finish_mkwrite_fault+0x300/0x300
> Oct 11 14:33:26 ubuntu kernel: [ 134.146975][T13860] ? find_held_lock+0x35/0x1e0
> Oct 11 14:33:26 ubuntu kernel: [ 134.146985][T13860] ? __do_page_fault+0x504/0xb60
> Oct 11 14:33:26 ubuntu kernel: [ 134.146994][T13860] ? lock_downgrade+0x900/0x900
> Oct 11 14:33:26 ubuntu kernel: [ 134.147002][T13860] ? __pmd_alloc+0x410/0x410
> Oct 11 14:33:26 ubuntu kernel: [ 134.147017][T13860] ? __kasan_check_write+0x14/0x20
> Oct 11 14:33:26 ubuntu kernel: [ 134.147024][T13860] ? up_read+0x1b6/0x7a0
> Oct 11 14:33:26 ubuntu kernel: [ 134.147033][T13860] ? down_read_nested+0x480/0x480
> Oct 11 14:33:26 ubuntu kernel: [ 134.147048][T13860] ? do_syscall_64+0x26/0x6a0
> Oct 11 14:33:26 ubuntu kernel: [ 134.147056][T13860] ? entry_SYSCALL_64_after_hwframe+0x49/0xbe
> Oct 11 14:33:26 ubuntu kernel: [ 134.147063][T13860] ? do_syscall_64+0x26/0x6a0
> Oct 11 14:33:26 ubuntu kernel: [ 134.147074][T13860] __x64_sys_bpf+0x73/0xb0
> Oct 11 14:33:26 ubuntu kernel: [ 134.147084][T13860] do_syscall_64+0xde/0x6a0
> Oct 11 14:33:26 ubuntu kernel: [ 134.147095][T13860] entry_SYSCALL_64_after_hwframe+0x49/0xbe
> (...snipped...)
> Oct 11 14:33:41 ubuntu kernel: [ 148.384539][ T4514] unregister_netdevice: waiting for bridge_slave_0 to become free. Usage count = 850 ffff888091fd2000
> ----------------------------------------
>