[syzbot] WARNING in nbd_dev_add (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    cb690f5238d7 Merge tag 'for-5.16/drivers-2021-11-09' of gi..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17736888b00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=9d7259f0deb293aa
dashboard link: https://syzkaller.appspot.com/bug?extid=5e8112c15ddb3db8416d
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5e8112c15ddb3db8416d@xxxxxxxxxxxxxxxxxxxxxxxxx

RDX: 0000000000000000 RSI: 0000000020000380 RDI: 0000000000000005
RBP: 00007f2388d2e1d0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000002
R13: 00007ffcef734a5f R14: 00007f2388d2e300 R15: 0000000000022000
 </TASK>
------------[ cut here ]------------
WARNING: CPU: 1 PID: 5223 at block/genhd.c:547 device_add_disk+0x338/0xef0 block/genhd.c:547
Modules linked in:
CPU: 1 PID: 5223 Comm: syz-executor.3 Not tainted 5.15.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:device_add_disk+0x338/0xef0 block/genhd.c:547
Code: 74 08 3c 03 0f 8e 93 09 00 00 8b 5d 00 bf 03 01 00 00 89 de e8 39 ee ae fd 81 fb 03 01 00 00 0f 84 16 02 00 00 e8 08 ec ae fd <0f> 0b 41 bc 01 00 00 00 e8 fb eb ae fd 44 89 e0 48 83 c4 38 5b 5d
RSP: 0018:ffffc90019027460 EFLAGS: 00010246
RAX: 0000000000040000 RBX: 000000000000002b RCX: ffffc9000fb72000
RDX: 0000000000040000 RSI: ffffffff83c8d798 RDI: 0000000000000003
RBP: ffff88807652f000 R08: 0000000000000103 R09: ffff888016beea43
R10: ffffffff83c8d787 R11: 0000000000000000 R12: 00000000ffffffea
R13: ffff88807652f080 R14: ffff88807652f008 R15: ffff888016beea08
FS:  00007f2388d2e700(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2bc23000 CR3: 0000000034919000 CR4: 0000000000350ee0
Call Trace:
 <TASK>
 add_disk include/linux/genhd.h:212 [inline]
 nbd_dev_add+0x8d9/0xcd0 drivers/block/nbd.c:1818
 nbd_genl_connect+0x11f3/0x1930 drivers/block/nbd.c:1948
 genl_family_rcv_msg_doit+0x228/0x320 net/netlink/genetlink.c:731
 genl_family_rcv_msg net/netlink/genetlink.c:775 [inline]
 genl_rcv_msg+0x328/0x580 net/netlink/genetlink.c:792
 netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2491
 genl_rcv+0x24/0x40 net/netlink/genetlink.c:803
 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]
 netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1345
 netlink_sendmsg+0x86d/0xda0 net/netlink/af_netlink.c:1916
 sock_sendmsg_nosec net/socket.c:704 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:724
 ____sys_sendmsg+0x6e8/0x810 net/socket.c:2409
 ___sys_sendmsg+0xf3/0x170 net/socket.c:2463
 __sys_sendmsg+0xe5/0x1b0 net/socket.c:2492
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f238b7b8ae9
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 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f2388d2e188 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f238b8cbf60 RCX: 00007f238b7b8ae9
RDX: 0000000000000000 RSI: 0000000020000380 RDI: 0000000000000005
RBP: 00007f2388d2e1d0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000002
R13: 00007ffcef734a5f R14: 00007f2388d2e300 R15: 0000000000022000
 </TASK>


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