------------[ cut here ]------------
WARNING: net/ipv4/ipmr.c:2302 at ip_mr_output+0xbb1/0xe70 net/ipv4/ipmr.c:2302, CPU#0: syz.4.235/6921
Modules linked in:
CPU: 0 UID: 0 PID: 6921 Comm: syz.4.235 Not tainted 6.16.0-rc3-next-20250623-syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:ip_mr_output+0xbb1/0xe70 net/ipv4/ipmr.c:2302
Code: df e9 63 f6 ff ff e8 7e a7 be f7 48 8b 74 24 18 45 31 f6 31 ff ba 02 00 00 00 e8 fa 09 4c ff e9 45 f6 ff ff e8 60 a7 be f7 90 <0f> 0b 90 e9 94 f5 ff ff e8 52 a7 be f7 90 0f 0b 90 42 80 3c 2b 00
RSP: 0018:ffffc90000007900 EFLAGS: 00010246
RAX: ffffffff8a012580 RBX: ffff88802e8d2c80 RCX: ffff8880245a5a00
RDX: 0000000000000100 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90000007a10 R08: ffff8880245a5a00 R09: 0000000000000004
R10: 0000000000000003 R11: ffffffff8a0119d0 R12: 0000000000000010
R13: dffffc0000000000 R14: ffff88803086c700 R15: 0000000000000000
FS:  00007f163b6b16c0(0000) GS:ffff888125c25000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00002000003bb030 CR3: 000000001beba000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 igmp_send_report+0x89e/0xdb0 net/ipv4/igmp.c:799
 igmp_timer_expire+0x204/0x510 net/ipv4/igmp.c:-1
 call_timer_fn+0x17b/0x5f0 kernel/time/timer.c:1747
 expire_timers kernel/time/timer.c:1798 [inline]
 __run_timers kernel/time/timer.c:2372 [inline]
 __run_timer_base+0x61a/0x860 kernel/time/timer.c:2384
 run_timer_base kernel/time/timer.c:2393 [inline]
 run_timer_softirq+0xb7/0x180 kernel/time/timer.c:2403
 handle_softirqs+0x283/0x870 kernel/softirq.c:579
 __do_softirq kernel/softirq.c:613 [inline]
 invoke_softirq kernel/softirq.c:453 [inline]
 __irq_exit_rcu+0xca/0x1f0 kernel/softirq.c:680
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:696
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1050 [inline]
 sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1050
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:__sanitizer_cov_trace_pc+0x3c/0x70 kernel/kcov.c:220
Code: 8b 15 38 e3 df 10 81 e2 00 01 ff 00 74 11 81 fa 00 01 00 00 75 35 83 b9 3c 16 00 00 00 74 2c 8b 91 18 16 00 00 83 fa 02 75 21 <48> 8b 91 20 16 00 00 48 8b 32 48 8d 7e 01 8b 89 1c 16 00 00 48 39
RSP: 0018:ffffc9000b217a38 EFLAGS: 00000246
RAX: ffffffff894a6833 RBX: 0000000000000000 RCX: ffff8880245a5a00
RDX: 0000000000000002 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc9000b217c30 R08: 0000000000000005 R09: 0000000000000003
R10: ffffc9000b217cf3 R11: fffff52001642fa0 R12: ffffc9000b217ce0
R13: dffffc0000000000 R14: 0000000000000002 R15: 1ffff92001642f50
 ___sys_recvmsg+0x193/0x510 net/socket.c:2874
 do_recvmmsg+0x307/0x770 net/socket.c:2969
 __sys_recvmmsg net/socket.c:3043 [inline]
 __do_sys_recvmmsg net/socket.c:3066 [inline]
 __se_sys_recvmmsg net/socket.c:3059 [inline]
 __x64_sys_recvmmsg+0x190/0x240 net/socket.c:3059
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f163a78e929
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f163b6b1038 EFLAGS: 00000246 ORIG_RAX: 000000000000012b
RAX: ffffffffffffffda RBX: 00007f163a9b5fa0 RCX: 00007f163a78e929
RDX: 0000000000010106 RSI: 00002000000000c0 RDI: 0000000000000003
RBP: 00007f163a810b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f163a9b5fa0 R15: 00007fffd05530a8
 </TASK>
----------------
Code disassembly (best guess):
   0:	8b 15 38 e3 df 10    	mov    0x10dfe338(%rip),%edx        # 0x10dfe33e
   6:	81 e2 00 01 ff 00    	and    $0xff0100,%edx
   c:	74 11                	je     0x1f
   e:	81 fa 00 01 00 00    	cmp    $0x100,%edx
  14:	75 35                	jne    0x4b
  16:	83 b9 3c 16 00 00 00 	cmpl   $0x0,0x163c(%rcx)
  1d:	74 2c                	je     0x4b
  1f:	8b 91 18 16 00 00    	mov    0x1618(%rcx),%edx
  25:	83 fa 02             	cmp    $0x2,%edx
  28:	75 21                	jne    0x4b
* 2a:	48 8b 91 20 16 00 00 	mov    0x1620(%rcx),%rdx <-- trapping instruction
  31:	48 8b 32             	mov    (%rdx),%rsi
  34:	48 8d 7e 01          	lea    0x1(%rsi),%rdi
  38:	8b 89 1c 16 00 00    	mov    0x161c(%rcx),%ecx
  3e:	48                   	rex.W
  3f:	39                   	.byte 0x39