==================================================================
BUG: KASAN: use-after-free in __read_once_size include/linux/compiler.h:185 [inline]
BUG: KASAN: use-after-free in atomic_read arch/x86/include/asm/atomic.h:27 [inline]
BUG: KASAN: use-after-free in refcount_dec_not_one+0x9a/0xc0 lib/refcount.c:270
Read of size 4 at addr ffff8880aea4eb18 by task syz-executor.0/16077

CPU: 1 PID: 16077 Comm: syz-executor.0 Not tainted 4.14.295-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/22/2022
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x1b2/0x281 lib/dump_stack.c:58
 print_address_description.cold+0x54/0x1d3 mm/kasan/report.c:252
 kasan_report_error.cold+0x8a/0x191 mm/kasan/report.c:351
 kasan_report mm/kasan/report.c:409 [inline]
 __asan_report_load4_noabort+0x68/0x70 mm/kasan/report.c:429
 __read_once_size include/linux/compiler.h:185 [inline]
 atomic_read arch/x86/include/asm/atomic.h:27 [inline]
 refcount_dec_not_one+0x9a/0xc0 lib/refcount.c:270
 refcount_dec_and_mutex_lock+0x1a/0x60 lib/refcount.c:309
 nbd_put drivers/block/nbd.c:228 [inline]
 nbd_genl_connect+0xce1/0x13e0 drivers/block/nbd.c:1903
 genl_family_rcv_msg+0x572/0xb20 net/netlink/genetlink.c:600
 genl_rcv_msg+0xaf/0x140 net/netlink/genetlink.c:625
 netlink_rcv_skb+0x125/0x390 net/netlink/af_netlink.c:2454
 genl_rcv+0x24/0x40 net/netlink/genetlink.c:636
 netlink_unicast_kernel net/netlink/af_netlink.c:1296 [inline]
 netlink_unicast+0x437/0x610 net/netlink/af_netlink.c:1322
 netlink_sendmsg+0x648/0xbc0 net/netlink/af_netlink.c:1893
 sock_sendmsg_nosec net/socket.c:646 [inline]
 sock_sendmsg+0xb5/0x100 net/socket.c:656
 ___sys_sendmsg+0x6c8/0x800 net/socket.c:2062
 __sys_sendmsg+0xa3/0x120 net/socket.c:2096
 SYSC_sendmsg net/socket.c:2107 [inline]
 SyS_sendmsg+0x27/0x40 net/socket.c:2103
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x7f2e067dd5a9
RSP: 002b:00007f2e05150168 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f2e068fdf80 RCX: 00007f2e067dd5a9
RDX: 0000000000000000 RSI: 0000000020000380 RDI: 0000000000000007
RBP: 00007f2e06838580 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffd279e724f R14: 00007f2e05150300 R15: 0000000000022000

Allocated by task 1:
 save_stack mm/kasan/kasan.c:447 [inline]
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xeb/0x160 mm/kasan/kasan.c:551
 kmem_cache_alloc_trace+0x131/0x3d0 mm/slab.c:3618
 kmalloc include/linux/slab.h:488 [inline]
 kzalloc include/linux/slab.h:661 [inline]
 nbd_dev_add+0x7c/0x800 drivers/block/nbd.c:1617
 nbd_init+0x15b/0x17a drivers/block/nbd.c:2310
 do_one_initcall+0x88/0x210 init/main.c:830
 do_initcall_level init/main.c:896 [inline]
 do_initcalls init/main.c:904 [inline]
 do_basic_setup init/main.c:922 [inline]
 kernel_init_freeable+0x565/0x626 init/main.c:1081
 kernel_init+0xd/0x161 init/main.c:1006
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404

Freed by task 16077:
 save_stack mm/kasan/kasan.c:447 [inline]
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0xc3/0x1a0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3496 [inline]
 kfree+0xc9/0x250 mm/slab.c:3815
 nbd_dev_remove drivers/block/nbd.c:223 [inline]
 nbd_put.part.0+0x100/0x140 drivers/block/nbd.c:231
 nbd_put drivers/block/nbd.c:267 [inline]
 nbd_config_put+0x51c/0x6c0 drivers/block/nbd.c:1172
 nbd_genl_connect+0xcb9/0x13e0 drivers/block/nbd.c:1901
 genl_family_rcv_msg+0x572/0xb20 net/netlink/genetlink.c:600
 genl_rcv_msg+0xaf/0x140 net/netlink/genetlink.c:625
 netlink_rcv_skb+0x125/0x390 net/netlink/af_netlink.c:2454
 genl_rcv+0x24/0x40 net/netlink/genetlink.c:636
 netlink_unicast_kernel net/netlink/af_netlink.c:1296 [inline]
 netlink_unicast+0x437/0x610 net/netlink/af_netlink.c:1322
 netlink_sendmsg+0x648/0xbc0 net/netlink/af_netlink.c:1893
 sock_sendmsg_nosec net/socket.c:646 [inline]
 sock_sendmsg+0xb5/0x100 net/socket.c:656
 ___sys_sendmsg+0x6c8/0x800 net/socket.c:2062
 __sys_sendmsg+0xa3/0x120 net/socket.c:2096
 SYSC_sendmsg net/socket.c:2107 [inline]
 SyS_sendmsg+0x27/0x40 net/socket.c:2103
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb

The buggy address belongs to the object at ffff8880aea4ea40
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 216 bytes inside of
 512-byte region [ffff8880aea4ea40, ffff8880aea4ec40)
The buggy address belongs to the page:
page:ffffea0002ba9380 count:1 mapcount:0 mapping:ffff8880aea4e040 index:0x0
flags: 0xfff00000000100(slab)
raw: 00fff00000000100 ffff8880aea4e040 0000000000000000 0000000100000006
raw: ffffea0002ba21e0 ffffea0002ba9560 ffff88813fe74940 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880aea4ea00: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
 ffff8880aea4ea80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880aea4eb00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff8880aea4eb80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880aea4ec00: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
==================================================================