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Date:   Tue, 22 Dec 2020 07:11:08 +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)

On Mon, Dec 21, 2020 at 01:25:47PM +0100, Oliver Hartkopp wrote:
> 
> 
> On 20.12.20 15:37, Oleksij Rempel wrote:
> > 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 :)
> 
> No, it is not.
> 
> Team and bonding devices copy elements like dev->type but do not take care
> about the CAN specific ml_priv.
> 
> I don't know if this is the case here. I can take a look later.

ok

> > > 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?
> 
> IMO the patch is still an improvement as it swaps the testing and reduces
> complexity.

ack. I'm ok with this patch.

> Regards,
> Oliver
> 
> > 
> > > 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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