[moderation] [net?] general protection fault in arp_create (4)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 70eda68668d1 Merge tag 'hid-for-linus-2026051401' of git:/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15f56e36580000
kernel config: https://syzkaller.appspot.com/x/.config?x=4caf64b1ee83dac0
dashboard link: https://syzkaller.appspot.com/bug?extid=f8c1872e82ba92d160a4
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
CC: [da...@davemloft.net dsa...@kernel.org edum...@google.com ho...@kernel.org ido...@nvidia.com ku...@kernel.org linux-...@vger.kernel.org net...@vger.kernel.org pab...@redhat.com]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/6f3c10169d74/disk-70eda686.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/67977be60189/vmlinux-70eda686.xz
kernel image: https://storage.googleapis.com/syzbot-assets/cf642084f321/bzImage-70eda686.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f8c187...@syzkaller.appspotmail.com

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000016: 0000 [#1] SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x00000000000000b0-0x00000000000000b7]
CPU: 1 UID: 0 PID: 37 Comm: kworker/u8:2 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Workqueue: bat_events batadv_bla_periodic_work
RIP: 0010:arp_create+0xb1/0x980 net/ipv4/arp.c:554
Code: 89 4c 24 78 4a 89 04 21 e8 8c f7 a0 f7 44 89 b4 24 a0 00 00 00 89 9c 24 b0 00 00 00 49 8d bf b4 00 00 00 48 89 f8 48 c1 e8 03 <42> 0f b6 04 20 84 c0 0f 85 15 06 00 00 41 0f b7 9f b4 00 00 00 49
RSP: 0018:ffffc90000ad7720 EFLAGS: 00010213
RAX: 0000000000000016 RBX: 0000000000000000 RCX: ffff8880202edc40
RDX: 0000000000000000 RSI: 0000000000000806 RDI: 00000000000000b4
RBP: ffffc90000ad7840 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffff5200015af20 R12: dffffc0000000000
R13: ffff88806501d0a0 R14: 0000000000000000 R15: 0000000000000000
FS: 0000000000000000(0000) GS:ffff88812538a000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000032000 CR3: 0000000022ee7000 CR4: 0000000000350ef0
Call Trace:
<TASK>
batadv_bla_send_claim+0x183/0xeb0 net/batman-adv/bridge_loop_avoidance.c:361
batadv_bla_send_loopdetect net/batman-adv/bridge_loop_avoidance.c:1402 [inline]
batadv_bla_periodic_work+0x654/0xae0 net/batman-adv/bridge_loop_avoidance.c:1492
process_one_work kernel/workqueue.c:3314 [inline]
process_scheduled_works+0xb5d/0x1860 kernel/workqueue.c:3397
worker_thread+0xa53/0xfc0 kernel/workqueue.c:3478
kthread+0x389/0x470 kernel/kthread.c:436
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:arp_create+0xb1/0x980 net/ipv4/arp.c:554
Code: 89 4c 24 78 4a 89 04 21 e8 8c f7 a0 f7 44 89 b4 24 a0 00 00 00 89 9c 24 b0 00 00 00 49 8d bf b4 00 00 00 48 89 f8 48 c1 e8 03 <42> 0f b6 04 20 84 c0 0f 85 15 06 00 00 41 0f b7 9f b4 00 00 00 49
RSP: 0018:ffffc90000ad7720 EFLAGS: 00010213
RAX: 0000000000000016 RBX: 0000000000000000 RCX: ffff8880202edc40
RDX: 0000000000000000 RSI: 0000000000000806 RDI: 00000000000000b4
RBP: ffffc90000ad7840 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffff5200015af20 R12: dffffc0000000000
R13: ffff88806501d0a0 R14: 0000000000000000 R15: 0000000000000000
FS: 0000000000000000(0000) GS:ffff88812538a000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000032000 CR3: 0000000022ee7000 CR4: 0000000000350ef0
----------------
Code disassembly (best guess):
0: 89 4c 24 78 mov %ecx,0x78(%rsp)
4: 4a 89 04 21 mov %rax,(%rcx,%r12,1)
8: e8 8c f7 a0 f7 call 0xf7a0f799
d: 44 89 b4 24 a0 00 00 mov %r14d,0xa0(%rsp)
14: 00
15: 89 9c 24 b0 00 00 00 mov %ebx,0xb0(%rsp)
1c: 49 8d bf b4 00 00 00 lea 0xb4(%r15),%rdi
23: 48 89 f8 mov %rdi,%rax
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 42 0f b6 04 20 movzbl (%rax,%r12,1),%eax <-- trapping instruction
2f: 84 c0 test %al,%al
31: 0f 85 15 06 00 00 jne 0x64c
37: 41 0f b7 9f b4 00 00 movzwl 0xb4(%r15),%ebx
3e: 00
3f: 49 rex.WB


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