linux-kernel - [syzbot] [net?] general protection fault in __igmp_group

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Message-ID: <683ed829.a00a0220.d8eae.006c.GAE@google.com>
Date: Tue, 03 Jun 2025 04:10:33 -0700
From: syzbot <syzbot+b7da0e231ae4e5a9917f@...kaller.appspotmail.com>
To: davem@...emloft.net, dsahern@...nel.org, edumazet@...gle.com, 
	horms@...nel.org, kuba@...nel.org, linux-kernel@...r.kernel.org, 
	netdev@...r.kernel.org, pabeni@...hat.com, syzkaller-bugs@...glegroups.com
Subject: [syzbot] [net?] general protection fault in __igmp_group_dropped

Hello,

syzbot found the following issue on:

HEAD commit:    d00a83477e7a Merge tag 'input-for-v6.16-rc0' of git://git...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12f0dc82580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=4df26174733e11f3
dashboard link: https://syzkaller.appspot.com/bug?extid=b7da0e231ae4e5a9917f
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-d00a8347.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9ac727dc51c3/vmlinux-d00a8347.xz
kernel image: https://storage.googleapis.com/syzbot-assets/8981faa6f0a2/bzImage-d00a8347.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b7da0e231ae4e5a9917f@...kaller.appspotmail.com

bridge0: port 2(bridge_slave_1) entered disabled state
bridge_slave_0: left allmulticast mode
bridge_slave_0: left promiscuous mode
bridge0: port 1(bridge_slave_0) entered disabled state
Oops: general protection fault, probably for non-canonical address 0xdffffc0000000021: 0000 [#1] SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000108-0x000000000000010f]
CPU: 0 UID: 0 PID: 6857 Comm: kworker/u32:24 Not tainted 6.15.0-syzkaller-10954-gd00a83477e7a #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Workqueue: netns cleanup_net
RIP: 0010:read_pnet include/net/net_namespace.h:409 [inline]
RIP: 0010:dev_net include/linux/netdevice.h:2713 [inline]
RIP: 0010:__igmp_group_dropped+0xcd/0xe80 net/ipv4/igmp.c:1298
Code: 3c 02 00 0f 85 10 0c 00 00 4d 8b 2c 24 e8 cb 5b 80 01 48 b8 00 00 00 00 00 fc ff df 49 8d bd 08 01 00 00 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 db 0b 00 00 48 8d bb db 00 00 00 4d 8b bd 08 01
RSP: 0018:ffffc9000408f5d8 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: ffff888062ee0600 RCX: ffffffff89fda2e7
RDX: 0000000000000021 RSI: ffffffff89fd05dc RDI: 0000000000000108
RBP: 1ffff92000811ebe R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: ffff888053fdf000
R13: 0000000000000000 R14: 0000000000000001 R15: ffff88802bef0418
FS:  0000000000000000(0000) GS:ffff8880d6765000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000000000 CR3: 000000000e382000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 igmp_group_dropped net/ipv4/igmp.c:1335 [inline]
 ip_mc_down+0xc0/0x3c0 net/ipv4/igmp.c:1829
 inetdev_event+0x3b2/0x18a0 net/ipv4/devinet.c:1642
 notifier_call_chain+0xbc/0x410 kernel/notifier.c:85
 call_netdevice_notifiers_info+0xbe/0x140 net/core/dev.c:2230
 call_netdevice_notifiers_extack net/core/dev.c:2268 [inline]
 call_netdevice_notifiers net/core/dev.c:2282 [inline]
 dev_close_many+0x319/0x630 net/core/dev.c:1785
 unregister_netdevice_many_notify+0x578/0x26f0 net/core/dev.c:12046
 ops_exit_rtnl_list net/core/net_namespace.c:188 [inline]
 ops_undo_list+0x8fc/0xab0 net/core/net_namespace.c:249
 cleanup_net+0x408/0x890 net/core/net_namespace.c:686
 process_one_work+0x9cf/0x1b70 kernel/workqueue.c:3238
 process_scheduled_works kernel/workqueue.c:3321 [inline]
 worker_thread+0x6c8/0xf10 kernel/workqueue.c:3402
 kthread+0x3c5/0x780 kernel/kthread.c:464
 ret_from_fork+0x5d7/0x6f0 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:read_pnet include/net/net_namespace.h:409 [inline]
RIP: 0010:dev_net include/linux/netdevice.h:2713 [inline]
RIP: 0010:__igmp_group_dropped+0xcd/0xe80 net/ipv4/igmp.c:1298
Code: 3c 02 00 0f 85 10 0c 00 00 4d 8b 2c 24 e8 cb 5b 80 01 48 b8 00 00 00 00 00 fc ff df 49 8d bd 08 01 00 00 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 db 0b 00 00 48 8d bb db 00 00 00 4d 8b bd 08 01
RSP: 0018:ffffc9000408f5d8 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: ffff888062ee0600 RCX: ffffffff89fda2e7
RDX: 0000000000000021 RSI: ffffffff89fd05dc RDI: 0000000000000108
RBP: 1ffff92000811ebe R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: ffff888053fdf000
R13: 0000000000000000 R14: 0000000000000001 R15: ffff88802bef0418
FS:  0000000000000000(0000) GS:ffff8880d6965000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000003233b000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	3c 02                	cmp    $0x2,%al
   2:	00 0f                	add    %cl,(%rdi)
   4:	85 10                	test   %edx,(%rax)
   6:	0c 00                	or     $0x0,%al
   8:	00 4d 8b             	add    %cl,-0x75(%rbp)
   b:	2c 24                	sub    $0x24,%al
   d:	e8 cb 5b 80 01       	call   0x1805bdd
  12:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
  19:	fc ff df
  1c:	49 8d bd 08 01 00 00 	lea    0x108(%r13),%rdi
  23:	48 89 fa             	mov    %rdi,%rdx
  26:	48 c1 ea 03          	shr    $0x3,%rdx
* 2a:	80 3c 02 00          	cmpb   $0x0,(%rdx,%rax,1) <-- trapping instruction
  2e:	0f 85 db 0b 00 00    	jne    0xc0f
  34:	48 8d bb db 00 00 00 	lea    0xdb(%rbx),%rdi
  3b:	4d                   	rex.WRB
  3c:	8b                   	.byte 0x8b
  3d:	bd                   	.byte 0xbd
  3e:	08 01                	or     %al,(%rcx)


---
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