Re: [syzbot] [net?] WARNING in rtnl_dellink (3)

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
WARNING in rtnl_dellink

------------[ cut here ]------------
WARNING: CPU: 1 PID: 5783 at net/core/dev.c:10876 unregister_netdevice_many_notify+0x14d8/0x19a0 net/core/dev.c:10876
Modules linked in:
CPU: 1 PID: 5783 Comm: syz-executor.0 Not tainted 6.5.0-rc4-syzkaller-00248-g048c796beb6e-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023
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:ffffc9000594f158 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 000000002b3eb101 RCX: 0000000000000000
RDX: ffff8880244fbb80 RSI: ffffffff8829a7b8 RDI: 0000000000000001
RBP: ffff88801f5cc000 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000094000 R12: ffff88802998fa00
R13: 0000000000000000 R14: 0000000000000002 R15: ffff88802998fa00
FS:  00007f7724c956c0(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000040 CR3: 0000000077189000 CR4: 0000000000350ee0
Call Trace:
 <TASK>
 rtnl_delete_link net/core/rtnetlink.c:3214 [inline]
 rtnl_dellink+0x3c1/0xae0 net/core/rtnetlink.c:3266
 rtnetlink_rcv_msg+0x439/0xd30 net/core/rtnetlink.c:6428
 netlink_rcv_skb+0x16b/0x440 net/netlink/af_netlink.c:2549
 netlink_unicast_kernel net/netlink/af_netlink.c:1339 [inline]
 netlink_unicast+0x539/0x800 net/netlink/af_netlink.c:1365
 netlink_sendmsg+0x93c/0xe30 net/netlink/af_netlink.c:1914
 sock_sendmsg_nosec net/socket.c:725 [inline]
 sock_sendmsg+0xd9/0x180 net/socket.c:748
 ____sys_sendmsg+0x6ac/0x940 net/socket.c:2494
 ___sys_sendmsg+0x135/0x1d0 net/socket.c:2548
 __sys_sendmsg+0x117/0x1e0 net/socket.c:2577
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f7723e7cae9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 90 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 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f7724c950c8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f7723f9bf80 RCX: 00007f7723e7cae9
RDX: 0000000000000000 RSI: 0000000020000140 RDI: 0000000000000003
RBP: 00007f7723ec847a R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000004d R14: 00007f7723f9bf80 R15: 00007ffec7033f18
 </TASK>


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=11b78d73a80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=fa5bd4cd5ab6259d
dashboard link: https://syzkaller.appspot.com/bug?extid=4b4f06495414e92701d5
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=17752973a80000