[syzbot] [wireless?] WARNING in rfkill_dev_uevent

[syzbot] [wireless?] WARNING in rfkill_dev_uevent

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    dda51b737216 tcp: check congestion control restriction first
git tree:       net
console+strace: https://syzkaller.appspot.com/x/log.txt?x=12607259580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d0f4f48df8e34eb3
dashboard link: https://syzkaller.appspot.com/bug?extid=56f5119a6b206041a6b7
compiler:       Debian clang version 22.1.8 (1~deb13u4), Debian LLD 22.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10e3188d580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=169b9135580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/69fc30a54172/disk-dda51b73.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6fd8743be1c2/vmlinux-dda51b73.xz
kernel image: https://storage.googleapis.com/syzbot-assets/1aa0f93cd3c4/bzImage-dda51b73.xz

AI-generated root cause summary:
In mac80211_hwsim and cfg80211, the netlink attribute HWSIM_ATTR_RADIO_NAME is
accepted without a length limit, and cfg80211 does not bound requested_name when
setting the device and rfkill names. When a user creates a virtual radio with an
excessively long name via netlink, rfkill registration triggers a uevent where
RFKILL_NAME exceeds the fixed 2048-byte UEVENT_BUFFER_SIZE in add_uevent_var(),
triggering a WARN. In production kernels, add_uevent_var() safely returns
-ENOMEM and drops the uevent without memory corruption or system crashes.

full analysis:  https://syzkaller.appspot.com/x/ai_root_cause?x=56f5119a6b206041a6b7

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+56f5119a6b206041a6b7@syzkaller.appspotmail.com

workqueue
workqueue: name exceeds WQ_NAME_LEN. Truncating to: \x14���e�45�8) r1 += -8
     15: .
------------[ cut here ]------------
add_uevent_var: buffer size too small
WARNING: lib/kobject_uevent.c:688 at add_uevent_var+0x2db/0x460 lib/kobject_uevent.c:688, CPU#0: syz-executor353/5646
Modules linked in:
CPU: 0 UID: 0 PID: 5646 Comm: syz-executor353 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026
RIP: 0010:add_uevent_var+0x2db/0x460 lib/kobject_uevent.c:688
Code: 48 8b 44 24 40 42 0f b6 04 38 84 c0 48 8b 5c 24 18 0f 85 73 01 00 00 44 01 33 31 c0 eb 20 e8 0c 1c dd f5 48 8d 3d 35 df a3 05 <67> 48 0f b9 3a b8 f4 ff ff ff 49 bf 00 00 00 00 00 fc ff df 66 43
RSP: 0018:ffffc90003996a00 EFLAGS: 00010293
RAX: ffffffff8beb4a14 RBX: 1ffff1100efa0443 RCX: ffff88807f68be80
RDX: 0000000000000000 RSI: 0000000000001770 RDI: ffffffff918f2950
RBP: ffffc90003996b38 R08: ffff88807f68be80 R09: 0000000000000008
R10: 0000000000000007 R11: 0000000000000000 R12: 0000000000001770
R13: 1ffff92000732d50 R14: 000000000000079e R15: 0000000000000062
FS:  000055556e425400(0000) GS:ffff888123a6b000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000069e000 CR3: 00000000713cc000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 rfkill_dev_uevent+0x2f/0x1f0 net/rfkill/core.c:875
 dev_uevent+0x4ab/0x870 drivers/base/core.c:2774
 kobject_uevent_env+0x475/0x9e0 lib/kobject_uevent.c:576
 device_add+0x544/0xb80 drivers/base/core.c:3742
 rfkill_register+0x170/0x9b0 net/rfkill/core.c:1100
 wiphy_register+0x2a5f/0x3290 net/wireless/core.c:1310
 ieee80211_register_hw+0x3d72/0x4b30 net/mac80211/main.c:1634
 mac80211_hwsim_new_radio+0x32f1/0x5990 drivers/net/wireless/virtual/mac80211_hwsim_main.c:6186
 hwsim_new_radio_nl+0xd8b/0xf90 drivers/net/wireless/virtual/mac80211_hwsim_main.c:7062
 genl_family_rcv_msg_doit+0x233/0x340 net/netlink/genetlink.c:1114
 genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline]
 genl_rcv_msg+0x614/0x7a0 net/netlink/genetlink.c:1209
 netlink_rcv_skb+0x226/0x4a0 net/netlink/af_netlink.c:2580
 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218
 netlink_unicast_kernel net/netlink/af_netlink.c:1335 [inline]
 netlink_unicast+0x8ef/0xa80 net/netlink/af_netlink.c:1361
 netlink_sendmsg+0x7f0/0xb20 net/netlink/af_netlink.c:1920
 sock_sendmsg_nosec+0x14e/0x190 net/socket.c:800
 __sock_sendmsg net/socket.c:818 [inline]
 ____sys_sendmsg+0x54e/0x850 net/socket.c:2715
 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2769
 __sys_sendmsg net/socket.c:2801 [inline]
 __do_sys_sendmsg net/socket.c:2806 [inline]
 __se_sys_sendmsg net/socket.c:2804 [inline]
 __x64_sys_sendmsg+0x1b1/0x290 net/socket.c:2804
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fbc181e2649
Code: c0 79 93 eb d5 48 8d 7c 1d 00 eb 99 0f 1f 44 00 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 d8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc9f9d5c88 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fbc181e2649
RDX: 0000000000000084 RSI: 0000200000000a00 RDI: 0000000000000004
RBP: 0000000000000000 R08: 0000000000000006 R09: 0000000000000006
R10: 0000000000000006 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fbc18275c40 R15: 0000000000000002
 </TASK>
----------------
Code disassembly (best guess):
   0:	48 8b 44 24 40       	mov    0x40(%rsp),%rax
   5:	42 0f b6 04 38       	movzbl (%rax,%r15,1),%eax
   a:	84 c0                	test   %al,%al
   c:	48 8b 5c 24 18       	mov    0x18(%rsp),%rbx
  11:	0f 85 73 01 00 00    	jne    0x18a
  17:	44 01 33             	add    %r14d,(%rbx)
  1a:	31 c0                	xor    %eax,%eax
  1c:	eb 20                	jmp    0x3e
  1e:	e8 0c 1c dd f5       	call   0xf5dd1c2f
  23:	48 8d 3d 35 df a3 05 	lea    0x5a3df35(%rip),%rdi        # 0x5a3df5f
* 2a:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2f:	b8 f4 ff ff ff       	mov    $0xfffffff4,%eax
  34:	49 bf 00 00 00 00 00 	movabs $0xdffffc0000000000,%r15
  3b:	fc ff df
  3e:	66                   	data16
  3f:	43                   	rex.XB


---
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