==================================================================
BUG: KASAN: use-after-free in ex_handler_refcount+0x164/0x1a0 arch/x86/mm/extable.c:49
Write of size 4 at addr ffff888086138b98 by task systemd-udevd/5661

CPU: 0 PID: 5661 Comm: systemd-udevd Not tainted 4.14.300-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
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_store4_noabort+0x68/0x70 mm/kasan/report.c:434
 ex_handler_refcount+0x164/0x1a0 arch/x86/mm/extable.c:49
 fixup_exception+0x8a/0xd0 arch/x86/mm/extable.c:197
 do_trap_no_signal arch/x86/kernel/traps.c:208 [inline]
 do_trap+0x61/0x250 arch/x86/kernel/traps.c:257
 do_error_trap+0x132/0x2d0 arch/x86/kernel/traps.c:301
 invalid_op+0x1b/0x40 arch/x86/entry/entry_64.S:967

Allocated by task 5531:
 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:1619
 nbd_genl_connect+0x3a4/0x13e0 drivers/block/nbd.c:1764
 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+0x5e/0xd3

Freed by task 5546:
 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:228 [inline]
 nbd_genl_connect+0xcf6/0x13e0 drivers/block/nbd.c:1905
 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+0x5e/0xd3

The buggy address belongs to the object at ffff888086138ac0
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 216 bytes inside of
 512-byte region [ffff888086138ac0, ffff888086138cc0)
The buggy address belongs to the page:
page:ffffea0002184e00 count:1 mapcount:0 mapping:ffff8880861380c0 index:0x0
flags: 0xfff00000000100(slab)
raw: 00fff00000000100 ffff8880861380c0 0000000000000000 0000000100000006
raw: ffffea0002cf3ce0 ffffea00024f48a0 ffff88813fe74940 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888086138a80: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
 ffff888086138b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888086138b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff888086138c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888086138c80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
==================================================================