[moderation] [net?] KASAN: null-ptr-deref Write in send_to_lecd

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: e5e09233e8a9 tools: ynl: add uns-admin-perm to genetlink
git tree: net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=132f08ba580000
kernel config: https://syzkaller.appspot.com/x/.config?x=779072223d02a312
dashboard link: https://syzkaller.appspot.com/bug?extid=54cbdda9d4a646b6f901
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
CC: [da...@davemloft.net edum...@google.com ho...@kernel.org 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/4e01abcaabc6/disk-e5e09233.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9388914b512b/vmlinux-e5e09233.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e3aab2f0e30a/bzImage-e5e09233.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+54cbdd...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: null-ptr-deref in instrument_atomic_read_write include/linux/instrumented.h:112 [inline]
BUG: KASAN: null-ptr-deref in atomic_add include/linux/atomic/atomic-instrumented.h:104 [inline]
BUG: KASAN: null-ptr-deref in atm_force_charge include/linux/atmdev.h:261 [inline]
BUG: KASAN: null-ptr-deref in send_to_lecd+0x2c2/0x600 net/atm/lec.c:535
Write of size 4 at addr 0000000000000140 by task aoe_tx0/1299

CPU: 1 UID: 0 PID: 1299 Comm: aoe_tx0 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
kasan_report+0x117/0x150 mm/kasan/report.c:595
check_region_inline mm/kasan/generic.c:-1 [inline]
kasan_check_range+0x264/0x2c0 mm/kasan/generic.c:200
instrument_atomic_read_write include/linux/instrumented.h:112 [inline]
atomic_add include/linux/atomic/atomic-instrumented.h:104 [inline]
atm_force_charge include/linux/atmdev.h:261 [inline]
send_to_lecd+0x2c2/0x600 net/atm/lec.c:535
lec_arp_resolve net/atm/lec.c:1791 [inline]
lec_start_xmit+0xec0/0x2660 net/atm/lec.c:285
__netdev_start_xmit include/linux/netdevice.h:5292 [inline]
netdev_start_xmit include/linux/netdevice.h:5301 [inline]
xmit_one net/core/dev.c:3871 [inline]
dev_hard_start_xmit+0x2d8/0x870 net/core/dev.c:3887
sch_direct_xmit+0x251/0x4c0 net/sched/sch_generic.c:372
__dev_xmit_skb net/core/dev.c:4186 [inline]
__dev_queue_xmit+0x1615/0x38d0 net/core/dev.c:4802
dev_queue_xmit include/linux/netdevice.h:3384 [inline]
tx+0x6b/0x190 drivers/block/aoe/aoenet.c:62
kthread+0x1e0/0x3f0 drivers/block/aoe/aoecmd.c:1241
kthread+0x388/0x470 kernel/kthread.c:436
ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
==================================================================


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[Aleksandr Nogikh]

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