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Date:   Sun, 20 Dec 2020 15:37:34 +0100
From:   Oleksij Rempel <o.rempel@...gutronix.de>
To:     Oliver Hartkopp <socketcan@...tkopp.net>
Cc:     linux@...pel-privat.de, mkl@...gutronix.de, robin@...tonic.nl,
        davem@...emloft.net,
        syzbot <syzbot+5138c4dd15a0401bec7b@...kaller.appspotmail.com>,
        hkallweit1@...il.com, kuba@...nel.org,
        syzkaller-bugs@...glegroups.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-can@...r.kernel.org,
        kernel@...gutronix.de
Subject: Re: general protection fault in j1939_netdev_notify (2)

Hello Oliver,

On Sun, Dec 20, 2020 at 02:18:27PM +0100, Oliver Hartkopp wrote:
> Hello Oleksij,
> 
> I assume there is some ndev->ml_priv value set - but not from a CAN
> netdevice.

it is kind of CAN device :)

> What was the reason to fiddle with the 'priv' stuff in j1939_netdev_notify()
> before checking if it was a CAN device?
> 
> Would this patch fix the issue then?

No, j1939_priv_get_by_ndev() already has an internal test for
ARPHRD_CAN. One of this tests can be removed, to make the code clear.
So, we get netdev with ARPHRD_CAN and ml_priv == something.

Right now I do not know how to fix it.

Ideas?

> diff --git a/net/can/j1939/main.c b/net/can/j1939/main.c
> index bb914d8b4216..6940f98b81fb 100644
> --- a/net/can/j1939/main.c
> +++ b/net/can/j1939/main.c
> @@ -348,26 +348,25 @@ static int j1939_netdev_notify(struct notifier_block
> *nb,
>  			       unsigned long msg, void *data)
>  {
>  	struct net_device *ndev = netdev_notifier_info_to_dev(data);
>  	struct j1939_priv *priv;
> 
> +	if (ndev->type != ARPHRD_CAN)
> +		goto notify_done;
> +
>  	priv = j1939_priv_get_by_ndev(ndev);
>  	if (!priv)
>  		goto notify_done;
> 
> -	if (ndev->type != ARPHRD_CAN)
> -		goto notify_put;
> -
>  	switch (msg) {
>  	case NETDEV_DOWN:
>  		j1939_cancel_active_session(priv, NULL);
>  		j1939_sk_netdev_event_netdown(priv);
>  		j1939_ecu_unmap_all(priv);
>  		break;
>  	}
> 
> -notify_put:
>  	j1939_priv_put(priv);
> 
>  notify_done:
>  	return NOTIFY_DONE;
>  }
> 
> If so, I can send a proper patch if you like.
> 
> Best regards,
> Oliver
> 
> 
> On 20.12.20 06:34, syzbot wrote:
> > Hello,
> > 
> > syzbot found the following issue on:
> > 
> > HEAD commit:    d635a69d Merge tag 'net-next-5.11' of git://git.kernel.org..
> > git tree:       upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=1315f123500000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=c3556e4856b17a95
> > dashboard link: https://syzkaller.appspot.com/bug?extid=5138c4dd15a0401bec7b
> > compiler:       clang version 11.0.0 (https://github.com/llvm/llvm-project.git ca2dcbd030eadbf0aa9b660efe864ff08af6e18b)
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12955123500000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10f2f30f500000
> > 
> > The issue was bisected to:
> > 
> > commit 497a5757ce4e8f37219a3989ac6a561eb9a8e6c7
> > Author: Heiner Kallweit <hkallweit1@...il.com>
> > Date:   Sat Nov 7 20:50:56 2020 +0000
> > 
> >      tun: switch to net core provided statistics counters
> > 
> > bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=143b845b500000
> > final oops:     https://syzkaller.appspot.com/x/report.txt?x=163b845b500000
> > console output: https://syzkaller.appspot.com/x/log.txt?x=123b845b500000
> > 
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+5138c4dd15a0401bec7b@...kaller.appspotmail.com
> > Fixes: 497a5757ce4e ("tun: switch to net core provided statistics counters")
> > 
> > general protection fault, probably for non-canonical address 0xe000080fe8c072f1: 0000 [#1] PREEMPT SMP KASAN
> > KASAN: probably user-memory-access in range [0x0000607f46039788-0x0000607f4603978f]
> > CPU: 1 PID: 8472 Comm: syz-executor635 Not tainted 5.10.0-syzkaller #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> > RIP: 0010:j1939_ndev_to_priv net/can/j1939/main.c:219 [inline]
> > RIP: 0010:j1939_priv_get_by_ndev_locked net/can/j1939/main.c:231 [inline]
> > RIP: 0010:j1939_priv_get_by_ndev net/can/j1939/main.c:243 [inline]
> > RIP: 0010:j1939_netdev_notify+0x115/0x320 net/can/j1939/main.c:353
> > Code: 00 74 08 48 89 df e8 ba 1e 48 f9 48 8b 1b 48 85 db 0f 84 f0 00 00 00 4c 89 64 24 08 48 81 c3 28 60 00 00 48 89 d8 48 c1 e8 03 <42> 80 3c 30 00 74 08 48 89 df e8 8c 1e 48 f9 4c 8b 23 4d 85 e4 0f
> > RSP: 0018:ffffc90000e9fd68 EFLAGS: 00010202
> > RAX: 00000c0fe8c072f1 RBX: 0000607f46039788 RCX: ffff88801456d040
> > RDX: ffff88801456d040 RSI: 0000000000000118 RDI: 0000000000000118
> > RBP: 0000000000000118 R08: ffffffff8870585d R09: fffff520001d3fa5
> > R10: fffff520001d3fa5 R11: 0000000000000000 R12: 0000000000000010
> > R13: 1ffff1100293e848 R14: dffffc0000000000 R15: ffff8880149f4244
> > FS:  0000000001d13880(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 0000000020000080 CR3: 000000001402f000 CR4: 00000000001506e0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > Call Trace:
> >   notifier_call_chain kernel/notifier.c:83 [inline]
> >   raw_notifier_call_chain+0xe7/0x170 kernel/notifier.c:410
> >   call_netdevice_notifiers_info net/core/dev.c:2022 [inline]
> >   call_netdevice_notifiers_extack net/core/dev.c:2034 [inline]
> >   call_netdevice_notifiers+0xeb/0x150 net/core/dev.c:2048
> >   __tun_chr_ioctl+0x2337/0x4860 drivers/net/tun.c:3093
> >   vfs_ioctl fs/ioctl.c:48 [inline]
> >   __do_sys_ioctl fs/ioctl.c:753 [inline]
> >   __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:739
> >   do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
> >   entry_SYSCALL_64_after_hwframe+0x44/0xa9
> > RIP: 0033:0x440359
> > Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00
> > RSP: 002b:00007fffd37b9c98 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> > RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000440359
> > RDX: 0000000000000118 RSI: 00000000400454cd RDI: 0000000000000003
> > RBP: 00000000006ca018 R08: 00000000004002c8 R09: 00000000004002c8
> > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401b60
> > R13: 0000000000401bf0 R14: 0000000000000000 R15: 0000000000000000
> > Modules linked in:
> > ---[ end trace 7688a2c3c10da2e1 ]---
> > RIP: 0010:j1939_ndev_to_priv net/can/j1939/main.c:219 [inline]
> > RIP: 0010:j1939_priv_get_by_ndev_locked net/can/j1939/main.c:231 [inline]
> > RIP: 0010:j1939_priv_get_by_ndev net/can/j1939/main.c:243 [inline]
> > RIP: 0010:j1939_netdev_notify+0x115/0x320 net/can/j1939/main.c:353
> > Code: 00 74 08 48 89 df e8 ba 1e 48 f9 48 8b 1b 48 85 db 0f 84 f0 00 00 00 4c 89 64 24 08 48 81 c3 28 60 00 00 48 89 d8 48 c1 e8 03 <42> 80 3c 30 00 74 08 48 89 df e8 8c 1e 48 f9 4c 8b 23 4d 85 e4 0f
> > RSP: 0018:ffffc90000e9fd68 EFLAGS: 00010202
> > RAX: 00000c0fe8c072f1 RBX: 0000607f46039788 RCX: ffff88801456d040
> > RDX: ffff88801456d040 RSI: 0000000000000118 RDI: 0000000000000118
> > RBP: 0000000000000118 R08: ffffffff8870585d R09: fffff520001d3fa5
> > R10: fffff520001d3fa5 R11: 0000000000000000 R12: 0000000000000010
> > R13: 1ffff1100293e848 R14: dffffc0000000000 R15: ffff8880149f4244
> > FS:  0000000001d13880(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 0000000020000080 CR3: 000000001402f000 CR4: 00000000001506e0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > 
> > 
> > ---
> > This report is generated by a bot. It may contain errors.
> > See https://goo.gl/tpsmEJ for more information about syzbot.
> > syzbot engineers can be reached at syzkaller@...glegroups.com.
> > 
> > syzbot will keep track of this issue. See:
> > https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> > For information about bisection process see: https://goo.gl/tpsmEJ#bisection
> > syzbot can test patches for this issue, for details see:
> > https://goo.gl/tpsmEJ#testing-patches
> > 
> 

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