KASAN: use-after-free Write in ex_handler_refcount (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 29c52025 Linux 4.14.221
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1608f4ccd00000
kernel config: https://syzkaller.appspot.com/x/.config?x=83f668f81cfc5600
dashboard link: https://syzkaller.appspot.com/bug?extid=503bc500eff20b70bf25
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=119396f2d00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1178ae60d00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+503bc5...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in ex_handler_refcount+0x164/0x1a0 arch/x86/mm/extable.c:49
Write of size 4 at addr ffff8880a989cb58 by task systemd-udevd/8363

CPU: 0 PID: 8363 Comm: systemd-udevd Not tainted 4.14.221-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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:964
RIP: 0010:flags_string.cold+0x1b15/0x6aa9
RSP: 0018:ffff8880ac217cd0 EFLAGS: 00010296
RAX: 0000000000000000 RBX: ffff8880a989cb58 RCX: ffff8880a989cb58
RDX: 0000000000000004 RSI: 0000000000000003 RDI: 0000000000000001
RBP: ffffffff89511120 R08: 0000000000000000 R09: 0000000000000002
R10: 0000000000000000 R11: ffff8880938ce540 R12: 0000000000000000
R13: ffff88808b5e7204 R14: ffffed10116bce8e R15: dffffc0000000000
nbd_put drivers/block/nbd.c:228 [inline]
nbd_release+0xf3/0x150 drivers/block/nbd.c:1446
__blkdev_put+0x5aa/0x800 fs/block_dev.c:1803
blkdev_close+0x86/0xb0 fs/block_dev.c:1875
__fput+0x25f/0x7a0 fs/file_table.c:210
task_work_run+0x11f/0x190 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:191 [inline]
exit_to_usermode_loop+0x1ad/0x200 arch/x86/entry/common.c:164
prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline]
syscall_return_slowpath arch/x86/entry/common.c:270 [inline]
do_syscall_64+0x4a3/0x640 arch/x86/entry/common.c:297
entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x7f89d6fa6270
RSP: 002b:00007ffc737fd6b8 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000007 RCX: 00007f89d6fa6270
RDX: 000000000aba9500 RSI: 0000000000000000 RDI: 0000000000000007
RBP: 00007f89d7e5f710 R08: 0000000000000045 R09: 0000000000000018
R10: 00005622f60cbc28 R11: 0000000000000246 R12: 0000000000000000
R13: 00005622f60c5180 R14: 0000000000000003 R15: 000000000000000e

Allocated by task 8327:
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:1611
nbd_genl_connect+0x3a4/0x1400 drivers/block/nbd.c:1756
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:2433
genl_rcv+0x24/0x40 net/netlink/genetlink.c:636
netlink_unicast_kernel net/netlink/af_netlink.c:1287 [inline]
netlink_unicast+0x437/0x610 net/netlink/af_netlink.c:1313
netlink_sendmsg+0x62e/0xb80 net/netlink/af_netlink.c:1878
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

Freed by task 8361:
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+0xfa9/0x1400 drivers/block/nbd.c:1896
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:2433
genl_rcv+0x24/0x40 net/netlink/genetlink.c:636
netlink_unicast_kernel net/netlink/af_netlink.c:1287 [inline]
netlink_unicast+0x437/0x610 net/netlink/af_netlink.c:1313
netlink_sendmsg+0x62e/0xb80 net/netlink/af_netlink.c:1878
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 ffff8880a989ca80
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 216 bytes inside of
512-byte region [ffff8880a989ca80, ffff8880a989cc80)
The buggy address belongs to the page:
page:ffffea0002a62700 count:1 mapcount:0 mapping:ffff8880a989c080 index:0xffff8880a989c580
flags: 0xfff00000000100(slab)
raw: 00fff00000000100 ffff8880a989c080 ffff8880a989c580 0000000100000002
raw: ffffea0002a89fa0 ffffea000297bc20 ffff88813fe80940 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8880a989ca00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8880a989ca80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880a989cb00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8880a989cb80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880a989cc00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


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