audit: type=1400 audit(1513079024.121:30): avc:  denied  { write } for  pid=4034 comm="syz-executor7" path="socket:[14368]" dev="sockfs" ino=14368 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_fib_lookup_socket permissive=1
==================================================================
BUG: KASAN: use-after-free in disk_unblock_events+0x51/0x60 block/genhd.c:1657
Read of size 8 at addr ffff8801d4cc0a28 by task blkid/4056

CPU: 1 PID: 4056 Comm: blkid Not tainted 4.15.0-rc3+ #128
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+0x194/0x257 lib/dump_stack.c:53
 print_address_description+0x73/0x250 mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report+0x25b/0x340 mm/kasan/report.c:409
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
 disk_unblock_events+0x51/0x60 block/genhd.c:1657
 __blkdev_get+0x869/0x10e0 fs/block_dev.c:1535
 blkdev_get+0x3a1/0xad0 fs/block_dev.c:1591
 blkdev_open+0x1e4/0x270 fs/block_dev.c:1749
 do_dentry_open+0x682/0xd70 fs/open.c:752
 vfs_open+0x107/0x230 fs/open.c:866
 do_last fs/namei.c:3379 [inline]
 path_openat+0x1157/0x3530 fs/namei.c:3519
 do_filp_open+0x25b/0x3b0 fs/namei.c:3554
 do_sys_open+0x502/0x6d0 fs/open.c:1059
 SYSC_open fs/open.c:1077 [inline]
 SyS_open+0x2d/0x40 fs/open.c:1072
 entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x7fbde08db120
RSP: 002b:00007ffd6e0ffcc8 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fbde08db120
RDX: 00007ffd6e101f42 RSI: 0000000000000000 RDI: 00007ffd6e101f42
RBP: 0000000000000000 R08: 0000000000000078 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000dd5030
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000005

Allocated by task 1:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
 kmem_cache_alloc_node_trace+0x150/0x760 mm/slab.c:3656
 kmalloc_node include/linux/slab.h:537 [inline]
 kzalloc_node include/linux/slab.h:699 [inline]
 __alloc_disk_node+0xb4/0x4e0 block/genhd.c:1400
 loop_add+0x44c/0xa70 drivers/block/loop.c:1808
 loop_init+0x1ae/0x20a drivers/block/loop.c:2054
 do_one_initcall+0x9e/0x330 init/main.c:831
 do_initcall_level init/main.c:897 [inline]
 do_initcalls init/main.c:905 [inline]
 do_basic_setup init/main.c:923 [inline]
 kernel_init_freeable+0x469/0x521 init/main.c:1071
 kernel_init+0x13/0x172 init/main.c:998
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:441

Freed by task 4056:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3491 [inline]
 kfree+0xca/0x250 mm/slab.c:3806
 disk_release+0x327/0x410 block/genhd.c:1249
 device_release+0x7c/0x210 drivers/base/core.c:814
 kobject_cleanup lib/kobject.c:648 [inline]
 kobject_release lib/kobject.c:677 [inline]
 kref_put include/linux/kref.h:70 [inline]
 kobject_put+0x14c/0x250 lib/kobject.c:694
 put_disk+0x23/0x30 block/genhd.c:1465
 __blkdev_get+0x7c9/0x10e0 fs/block_dev.c:1528
 blkdev_get+0x3a1/0xad0 fs/block_dev.c:1591
 blkdev_open+0x1e4/0x270 fs/block_dev.c:1749
 do_dentry_open+0x682/0xd70 fs/open.c:752
 vfs_open+0x107/0x230 fs/open.c:866
 do_last fs/namei.c:3379 [inline]
 path_openat+0x1157/0x3530 fs/namei.c:3519
 do_filp_open+0x25b/0x3b0 fs/namei.c:3554
 do_sys_open+0x502/0x6d0 fs/open.c:1059
 SYSC_open fs/open.c:1077 [inline]
 SyS_open+0x2d/0x40 fs/open.c:1072
 entry_SYSCALL_64_fastpath+0x1f/0x96

The buggy address belongs to the object at ffff8801d4cc0400
 which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 1576 bytes inside of
 2048-byte region [ffff8801d4cc0400, ffff8801d4cc0c00)
The buggy address belongs to the page:
page:000000005359df8c count:1 mapcount:0 mapping:00000000c641b7cb index:0x0 compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801d4cc0400 0000000000000000 0000000100000003
raw: ffffea0007532c20 ffffea00075330a0 ffff8801db000c40 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801d4cc0900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801d4cc0980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801d4cc0a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                  ^
 ffff8801d4cc0a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801d4cc0b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================