[syzbot] [net?] WARNING in ip_rt_bug (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: fcee7d82f27d Merge tag 'net-7.1-rc3' of git://git.kernel.o..
git tree: net
console output: https://syzkaller.appspot.com/x/log.txt?x=139c40ec580000
kernel config: https://syzkaller.appspot.com/x/.config?x=4caf64b1ee83dac0
dashboard link: https://syzkaller.appspot.com/bug?extid=c13a57c2639c2c0d03a6
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15d3e56a580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1177bb26580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7b61ce97ed88/disk-fcee7d82.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a3d680659d25/vmlinux-fcee7d82.xz
kernel image: https://storage.googleapis.com/syzbot-assets/16070336dc25/bzImage-fcee7d82.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c13a57...@syzkaller.appspotmail.com

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1
WARNING: net/ipv4/route.c:1275 at ip_rt_bug+0x2d/0x140 net/ipv4/route.c:1275, CPU#1: syz.0.17/5858
Modules linked in:
CPU: 1 UID: 0 PID: 5858 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:ip_rt_bug+0x2d/0x140 net/ipv4/route.c:1275
Code: fa 55 41 57 41 56 41 55 41 54 53 48 89 d3 e8 0a fb b8 f7 66 90 e8 03 fb b8 f7 31 ff 48 89 de ba 02 00 00 00 e8 84 81 68 ff 90 <0f> 0b 90 31 c0 5b 41 5c 41 5d 41 5e 41 5f 5d e9 0f d3 9e 01 cc 49
RSP: 0018:ffffc900032ef1c0 EFLAGS: 00010286
RAX: f1fcc608b0941b00 RBX: ffff8880750b3000 RCX: 0000000080000401
RDX: 0000000000000002 RSI: ffffffff8dfa6610 RDI: ffffffff8c28ade0
RBP: ffffc900032ef4c0 R08: ffffffff9030adf7 R09: 1ffffffff20615be
R10: dffffc0000000000 R11: fffffbfff20615bf R12: dffffc0000000000
R13: 0000000000000000 R14: ffff8880750b3000 R15: dffffc0000000000
FS: 0000555579ced500(0000) GS:ffff88812538d000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fbd90672700 CR3: 0000000072438000 CR4: 00000000003526f0
Call Trace:
<TASK>
ip_send_skb net/ipv4/ip_output.c:1510 [inline]
ip_push_pending_frames+0x8b/0x110 net/ipv4/ip_output.c:1530
__icmp_send+0x11e4/0x1690 net/ipv4/icmp.c:1000
icmp_send include/net/icmp.h:43 [inline]
ip_options_compile+0x80/0xb0 net/ipv4/ip_options.c:473
ip_rcv_options net/ipv4/ip_input.c:290 [inline]
ip_rcv_finish_core+0xaa2/0x1c00 net/ipv4/ip_input.c:430
ip_rcv_finish+0x14c/0x2a0 net/ipv4/ip_input.c:490
NF_HOOK+0x336/0x3c0 include/linux/netfilter.h:318
__netif_receive_skb_one_core net/core/dev.c:6202 [inline]
__netif_receive_skb net/core/dev.c:6315 [inline]
netif_receive_skb_internal net/core/dev.c:6401 [inline]
netif_receive_skb+0x45b/0xbf0 net/core/dev.c:6460
tun_rx_batched+0x1de/0x790 drivers/net/tun.c:1487
tun_get_user+0x2bbc/0x43e0 drivers/net/tun.c:1955
tun_chr_write_iter+0x113/0x200 drivers/net/tun.c:2001
new_sync_write fs/read_write.c:595 [inline]
vfs_write+0x61d/0xb90 fs/read_write.c:688
ksys_write+0x150/0x270 fs/read_write.c:740
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fbd9075d60e
Code: 08 0f 85 a5 a8 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 <c3> 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 80 00 00 00 00 48 83 ec 08
RSP: 002b:00007ffcba496af8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000555579ced500 RCX: 00007fbd9075d60e
RDX: 0000000000000046 RSI: 0000200000000400 RDI: 00000000000000c8
RBP: 00007fbd90832d69 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fbd90a15fac R14: 00007fbd90a15fa0 R15: 00007fbd90a15fa0
</TASK>


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