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 <20180426061314.GH20683@leo.usersys.redhat.com>
From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Thu, 26 Apr 2018 10:04:16 +0200
Message-ID: <CACT4Y+aDko-kKP-u2S_UGBbB-uwnGw4dWTOSmXVDR3=osLJeFg@mail.gmail.com>
Subject: Re: WARNING: kobject bug in br_add_if
To:     Hangbin Liu <liuhangbin@gmail.com>
Cc:     syzbot <syzbot+de73361ee4971b6e6f75@syzkaller.appspotmail.com>,
        bridge@lists.linux-foundation.org,
        David Miller <davem@davemloft.net>,
        LKML <linux-kernel@vger.kernel.org>,
        netdev <netdev@vger.kernel.org>,
        stephen hemminger <stephen@networkplumber.org>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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On Thu, Apr 26, 2018 at 8:13 AM, Hangbin Liu <liuhangbin@gmail.com> wrote:
> On Wed, Apr 11, 2018 at 05:18:23PM +0200, Dmitry Vyukov wrote:
>> On Wed, Apr 11, 2018 at 5:15 PM, syzbot
>> <syzbot+de73361ee4971b6e6f75@syzkaller.appspotmail.com> wrote:
>> > Hello,
>> >
>> > syzbot hit the following crash on upstream commit
>> > 10b84daddbec72c6b440216a69de9a9605127f7a (Sat Mar 31 17:59:00 2018 +0000)
>> > Merge branch 'perf-urgent-for-linus' of
>> > git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
>> > syzbot dashboard link:
>> > https://syzkaller.appspot.com/bug?extid=de73361ee4971b6e6f75
>> >
>> > So far this crash happened 4 times on net-next, upstream.
>> > Unfortunately, I don't have any reproducer for this crash yet.
>> > Raw console output:
>> > https://syzkaller.appspot.com/x/log.txt?id=5007286875455488
>> > Kernel config:
>> > https://syzkaller.appspot.com/x/.config?id=-2760467897697295172
>> > compiler: gcc (GCC) 7.1.1 20170620
>> >
>> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
>> > Reported-by: syzbot+de73361ee4971b6e6f75@syzkaller.appspotmail.com
>> > It will help syzbot understand when the bug is fixed. See footer for
>> > details.
>> > If you forward the report, please keep this part and the footer.
>>
>> +Greg
>>
>> The plan is to remove this WARNING from kobject_add, if there are no objections.
>
> Hi Dmitry,
>
> For this bug, why should we remove the WARNING instead of adding a check in
> br_add_if()? Something like


Mainline because nobody wants to fix these.
If you think this is a real bug and you are ready to fix it, please
mail an official patch.


> diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c
> index 82c1a6f..79dcc3d 100644
> --- a/net/bridge/br_if.c
> +++ b/net/bridge/br_if.c
> @@ -518,8 +518,8 @@ int br_add_if(struct net_bridge *br, struct net_device *dev,
>                 return -ELOOP;
>         }
>
> -       /* Device is already being bridged */
> -       if (br_port_exists(dev))
> +       /* Device still has master upper dev */
> +       if (netdev_master_upper_dev_get(dev))
>                 return -EBUSY;
>
>         /* No bridging devices that dislike that (e.g. wireless) */
>
> Thanks
> Hangbin
>>
>> > ------------[ cut here ]------------
>> > binder: 23650:23651 unknown command 1078223622
>> > kobject_add_internal failed for brport (error: -12 parent: bond0)
>> > binder: 23650:23651 ioctl c0306201 2000dfd0 returned -22
>> > WARNING: CPU: 1 PID: 23647 at lib/kobject.c:242
>> > kobject_add_internal+0x3f6/0xbc0 lib/kobject.c:240
>> > Kernel panic - not syncing: panic_on_warn set ...
>> >
>> > CPU: 1 PID: 23647 Comm: syz-executor7 Not tainted 4.16.0-rc7+ #374
>> > binder: BINDER_SET_CONTEXT_MGR already set
>> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
>> > Google 01/01/2011
>> > Call Trace:
>> >  __dump_stack lib/dump_stack.c:17 [inline]
>> >  dump_stack+0x194/0x24d lib/dump_stack.c:53
>> >  panic+0x1e4/0x41c kernel/panic.c:183
>> >  __warn+0x1dc/0x200 kernel/panic.c:547
>> >  report_bug+0x1f4/0x2b0 lib/bug.c:186
>> >  fixup_bug.part.10+0x37/0x80 arch/x86/kernel/traps.c:178
>> >  fixup_bug arch/x86/kernel/traps.c:247 [inline]
>> >  do_error_trap+0x2d7/0x3e0 arch/x86/kernel/traps.c:296
>> >  do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:315
>> >  invalid_op+0x1b/0x40 arch/x86/entry/entry_64.S:986
>> > RIP: 0010:kobject_add_internal+0x3f6/0xbc0 lib/kobject.c:240
>> > RSP: 0018:ffff8801d089f560 EFLAGS: 00010286
>> > RAX: dffffc0000000008 RBX: ffff8801adbee178 RCX: ffffffff815b193e
>> > RDX: 0000000000040000 RSI: ffffc900022aa000 RDI: 1ffff1003a113e31
>> > RBP: ffff8801d089f658 R08: 1ffff1003a113df3 R09: 0000000000000000
>> > R10: 0000000000000000 R11: 0000000000000000 R12: 1ffff1003a113eb2
>> > R13: 00000000fffffff4 R14: ffff8801abd88828 R15: ffff8801d75a1e00
>> >  kobject_add_varg lib/kobject.c:364 [inline]
>> >  kobject_init_and_add+0xf9/0x150 lib/kobject.c:436
>> >  br_add_if+0x79a/0x1a70 net/bridge/br_if.c:533
>> >  add_del_if+0xf4/0x140 net/bridge/br_ioctl.c:101
>> >  br_dev_ioctl+0xa2/0xc0 net/bridge/br_ioctl.c:396
>> >  dev_ifsioc+0x333/0x9b0 net/core/dev_ioctl.c:334
>> >  dev_ioctl+0x176/0xbe0 net/core/dev_ioctl.c:500
>> >  sock_do_ioctl+0x1ba/0x390 net/socket.c:981
>> >  sock_ioctl+0x367/0x670 net/socket.c:1081
>> >  vfs_ioctl fs/ioctl.c:46 [inline]
>> >  do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:686
>> >  SYSC_ioctl fs/ioctl.c:701 [inline]
>> >  SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
>> >  do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
>> >  entry_SYSCALL_64_after_hwframe+0x42/0xb7
>> > RIP: 0033:0x454e79
>> > RSP: 002b:00007eff7dab7c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
>> > RAX: ffffffffffffffda RBX: 00007eff7dab86d4 RCX: 0000000000454e79
>> > RDX: 0000000020000000 RSI: 00000000000089a2 RDI: 0000000000000014
>> > RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000
>> > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000015
>> > R13: 0000000000000369 R14: 00000000006f7278 R15: 0000000000000006
>> > Dumping ftrace buffer:
>> >    (ftrace buffer empty)
>> > Kernel Offset: disabled
>> > Rebooting in 86400 seconds..