[syzbot] [net?] WARNING in ip6_tnl_exit_batch_net

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 048c796beb6e ipv6: adjust ndisc_is_useropt() to also retur..
git tree: net
console+strace: https://syzkaller.appspot.com/x/log.txt?x=103213a5a80000
kernel config: https://syzkaller.appspot.com/x/.config?x=fa5bd4cd5ab6259d
dashboard link: https://syzkaller.appspot.com/bug?extid=d810d3cd45ed1848c3f7
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1475a873a80000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=153cc91ba80000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/bf6b84b5998f/disk-048c796b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/4000dee89ebe/vmlinux-048c796b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b700ee9bd306/bzImage-048c796b.xz

The issue was bisected to:

commit 718cb09aaa6fa78cc8124e9517efbc6c92665384
Author: Vlad Buslov <vla...@nvidia.com>
Date: Tue Aug 8 09:35:21 2023 +0000

vlan: Fix VLAN 0 memory leak

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=12cbf169a80000
final oops: https://syzkaller.appspot.com/x/report.txt?x=11cbf169a80000
console output: https://syzkaller.appspot.com/x/log.txt?x=16cbf169a80000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d810d3...@syzkaller.appspotmail.com
Fixes: 718cb09aaa6f ("vlan: Fix VLAN 0 memory leak")

------------[ cut here ]------------
WARNING: CPU: 0 PID: 12 at net/core/dev.c:10876 unregister_netdevice_many_notify+0x14d8/0x19a0 net/core/dev.c:10876
Modules linked in:
CPU: 0 PID: 12 Comm: kworker/u4:1 Not tainted 6.5.0-rc4-syzkaller-00248-g048c796beb6e #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023
Workqueue: netns cleanup_net
RIP: 0010:unregister_netdevice_many_notify+0x14d8/0x19a0 net/core/dev.c:10876
Code: b4 1a 00 00 48 c7 c6 e0 18 81 8b 48 c7 c7 20 19 81 8b c6 05 ab 19 6c 06 01 e8 b4 22 23 f9 0f 0b e9 64 f7 ff ff e8 68 60 5c f9 <0f> 0b e9 3b f7 ff ff e8 fc 68 b0 f9 e9 fc ec ff ff 4c 89 e7 e8 4f
RSP: 0018:ffffc90000117a30 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 0000000070de5201 RCX: 0000000000000000
RDX: ffff88801526d940 RSI: ffffffff8829a7b8 RDI: 0000000000000001
RBP: ffff88807d7ee000 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: ffffffff81004e11 R12: ffff888018fb2a00
R13: 0000000000000000 R14: 0000000000000002 R15: ffff888018fb2a00
FS: 0000000000000000(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005581d741a950 CR3: 000000007deef000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
ip6_tnl_exit_batch_net+0x57d/0x6f0 net/ipv6/ip6_tunnel.c:2278
ops_exit_list+0x125/0x170 net/core/net_namespace.c:175
cleanup_net+0x505/0xb20 net/core/net_namespace.c:614
process_one_work+0xaa2/0x16f0 kernel/workqueue.c:2597
worker_thread+0x687/0x1110 kernel/workqueue.c:2748
kthread+0x33a/0x430 kernel/kthread.c:389
ret_from_fork+0x2c/0x70 arch/x86/kernel/process.c:145
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304
</TASK>


---
This report is generated by a bot. It may contain errors.
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For information about bisection process see: https://goo.gl/tpsmEJ#bisection

If the bug is already fixed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

If you want to change bug's subsystems, reply with:
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(See the list of subsystem names on the web dashboard)

If the bug is a duplicate of another bug, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

[Ido Schimmel]

On Fri, Aug 11, 2023 at 06:57:07AM -0700, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 048c796beb6e ipv6: adjust ndisc_is_useropt() to also retur..
> git tree: net
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=103213a5a80000
> kernel config: https://syzkaller.appspot.com/x/.config?x=fa5bd4cd5ab6259d
> dashboard link: https://syzkaller.appspot.com/bug?extid=d810d3cd45ed1848c3f7
> compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1475a873a80000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=153cc91ba80000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/bf6b84b5998f/disk-048c796b.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/4000dee89ebe/vmlinux-048c796b.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/b700ee9bd306/bzImage-048c796b.xz
>
> The issue was bisected to:
>
> commit 718cb09aaa6fa78cc8124e9517efbc6c92665384
> Author: Vlad Buslov <vla...@nvidia.com>
> Date: Tue Aug 8 09:35:21 2023 +0000
>
> vlan: Fix VLAN 0 memory leak

I wasn't able to reproduce using the C reproducer, but I'm pretty sure I
know what is the problem. I wasn't aware that user space can create VLAN
devices with VID 0, which can result in the VLAN driver wrongly deleting
it upon NETDEV_DOWN. Reproduced using:

ip link add name dummy1 up type dummy
ip link add link dummy1 name dummy1.0 type vlan id 0
ip link del dev dummy1

Always adding VID 0 on NETDEV_UP "solves" the problem, but it will
increase the memory consumption for each netdev, which is not ideal. A
possible solution is trying to delete VID 0 upon NETDEV_UNREGISTER
instead of only iterating over upper VLAN devices.

Anyway, Vlad, it's probably best to send a revert while we figure it
out.

[Vlad Buslov]

Will do.

[Hillf Danton]

On Fri, 11 Aug 2023 06:57:07 -0700

> HEAD commit: 048c796beb6e ipv6: adjust ndisc_is_useropt() to also retur..
> git tree: net

> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=153cc91ba80000

Try to revert 718cb09aaa6f

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git 048c796beb6e

--- x/net/8021q/vlan.c
+++ y/net/8021q/vlan.c
@@ -384,7 +384,7 @@ static int vlan_device_event(struct noti
dev->name);
vlan_vid_add(dev, htons(ETH_P_8021Q), 0);
}
- if (event == NETDEV_DOWN)
+ if (event == NETDEV_DOWN && (dev->features & NETIF_F_HW_VLAN_CTAG_FILTER))
vlan_vid_del(dev, htons(ETH_P_8021Q), 0);

vlan_info = rtnl_dereference(dev->vlan_info);
@@ -486,6 +486,7 @@ static int vlan_device_event(struct noti
break;
}
unregister_netdevice_many(&list);
+ vlan_vid_del(dev, htons(ETH_P_8021Q), 0);
break;

case NETDEV_PRE_TYPE_CHANGE:
--

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+d810d3...@syzkaller.appspotmail.com

Tested on:

commit: 048c796b ipv6: adjust ndisc_is_useropt() to also retur..
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git
console output: https://syzkaller.appspot.com/x/log.txt?x=10a16cada80000

kernel config: https://syzkaller.appspot.com/x/.config?x=fa5bd4cd5ab6259d
dashboard link: https://syzkaller.appspot.com/bug?extid=d810d3cd45ed1848c3f7
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=1664153ba80000

Note: testing is done by a robot and is best-effort only.