==================================================================
BUG: KASAN: use-after-free in disk_unblock_events+0x55/0x60 block/genhd.c:1543
Read of size 8 at addr ffff8801cf099668 by task syz-executor.0/2128

CPU: 0 PID: 2128 Comm: syz-executor.0 Not tainted 4.4.174+ #17
 0000000000000000 66fd7a538dc6ed2f ffff8800a81ef6c0 ffffffff81aad1a1
 0000000000000000 ffffea00073c2600 ffff8801cf099668 0000000000000008
 0000000000000000 ffff8800a81ef6f8 ffffffff81490120 0000000000000000
Call Trace:
 [<ffffffff81aad1a1>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81aad1a1>] dump_stack+0xc1/0x120 lib/dump_stack.c:51
 [<ffffffff81490120>] print_address_description+0x6f/0x21b mm/kasan/report.c:252
 [<ffffffff81490358>] kasan_report_error mm/kasan/report.c:351 [inline]
 [<ffffffff81490358>] kasan_report mm/kasan/report.c:408 [inline]
 [<ffffffff81490358>] kasan_report.cold+0x8c/0x2be mm/kasan/report.c:393
 [<ffffffff81484ed4>] __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:429
 [<ffffffff81a82965>] disk_unblock_events+0x55/0x60 block/genhd.c:1543
 [<ffffffff8154efcc>] __blkdev_get+0x70c/0xdf0 fs/block_dev.c:1297
 [<ffffffff81551938>] blkdev_get+0x2e8/0x920 fs/block_dev.c:1353
 [<ffffffff8155219a>] blkdev_open+0x1aa/0x250 fs/block_dev.c:1508
 [<ffffffff8149154f>] do_dentry_open+0x38f/0xbd0 fs/open.c:749
 [<ffffffff81494d3b>] vfs_open+0x10b/0x210 fs/open.c:862
 [<ffffffff814c5ddf>] do_last fs/namei.c:3269 [inline]
 [<ffffffff814c5ddf>] path_openat+0x136f/0x4470 fs/namei.c:3406
 [<ffffffff814ccab1>] do_filp_open+0x1a1/0x270 fs/namei.c:3440
 [<ffffffff81495668>] do_sys_open+0x2f8/0x600 fs/open.c:1038
 [<ffffffff81599c4a>] C_SYSC_open fs/compat.c:1092 [inline]
 [<ffffffff81599c4a>] compat_SyS_open+0x2a/0x40 fs/compat.c:1090
 [<ffffffff8100603d>] do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
 [<ffffffff8100603d>] do_fast_syscall_32+0x32d/0xa90 arch/x86/entry/common.c:397
 [<ffffffff8271a350>] sysenter_flags_fixed+0xd/0x1a

Allocated by task 25112:
 [<ffffffff8102e3c6>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff81483f22>] save_stack mm/kasan/kasan.c:512 [inline]
 [<ffffffff81483f22>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff81483f22>] kasan_kmalloc.part.0+0x62/0xf0 mm/kasan/kasan.c:616
 [<ffffffff81484197>] kasan_kmalloc+0xb7/0xd0 mm/kasan/kasan.c:601
 [<ffffffff814801a3>] kmem_cache_alloc_trace+0x123/0x2d0 mm/slub.c:2642
 [<ffffffff81a81b50>] kmem_cache_alloc_node_trace include/linux/slab.h:367 [inline]
 [<ffffffff81a81b50>] kmalloc_node include/linux/slab.h:514 [inline]
 [<ffffffff81a81b50>] kzalloc_node include/linux/slab.h:631 [inline]
 [<ffffffff81a81b50>] alloc_disk_node+0x50/0x3c0 block/genhd.c:1282
 [<ffffffff81a81edb>] alloc_disk+0x1b/0x20 block/genhd.c:1274
 [<ffffffff81d436d0>] loop_add+0x380/0x830 drivers/block/loop.c:1857
 [<ffffffff81d43f44>] loop_probe+0x154/0x180 drivers/block/loop.c:1963
 [<ffffffff81d0efb1>] kobj_lookup+0x221/0x410 drivers/base/map.c:124
 [<ffffffff81a7fe3c>] get_gendisk+0x3c/0x2e0 block/genhd.c:689
 [<ffffffff8154ec5c>] __blkdev_get+0x39c/0xdf0 fs/block_dev.c:1193
 [<ffffffff81551938>] blkdev_get+0x2e8/0x920 fs/block_dev.c:1353
 [<ffffffff8155219a>] blkdev_open+0x1aa/0x250 fs/block_dev.c:1508
 [<ffffffff8149154f>] do_dentry_open+0x38f/0xbd0 fs/open.c:749
 [<ffffffff81494d3b>] vfs_open+0x10b/0x210 fs/open.c:862
 [<ffffffff814c5ddf>] do_last fs/namei.c:3269 [inline]
 [<ffffffff814c5ddf>] path_openat+0x136f/0x4470 fs/namei.c:3406
 [<ffffffff814ccab1>] do_filp_open+0x1a1/0x270 fs/namei.c:3440
 [<ffffffff81495668>] do_sys_open+0x2f8/0x600 fs/open.c:1038
 [<ffffffff81599c4a>] C_SYSC_open fs/compat.c:1092 [inline]
 [<ffffffff81599c4a>] compat_SyS_open+0x2a/0x40 fs/compat.c:1090
 [<ffffffff8100603d>] do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
 [<ffffffff8100603d>] do_fast_syscall_32+0x32d/0xa90 arch/x86/entry/common.c:397
 [<ffffffff8271a350>] sysenter_flags_fixed+0xd/0x1a

Freed by task 2128:
 [<ffffffff8102e3c6>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff81484820>] save_stack mm/kasan/kasan.c:512 [inline]
 [<ffffffff81484820>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff81484820>] kasan_slab_free+0xb0/0x190 mm/kasan/kasan.c:589
 [<ffffffff81481c44>] slab_free_hook mm/slub.c:1383 [inline]
 [<ffffffff81481c44>] slab_free_freelist_hook mm/slub.c:1405 [inline]
 [<ffffffff81481c44>] slab_free mm/slub.c:2859 [inline]
 [<ffffffff81481c44>] kfree+0xf4/0x310 mm/slub.c:3749
 [<ffffffff81a80375>] disk_release+0x255/0x330 block/genhd.c:1118
 [<ffffffff81cf785d>] device_release+0x7d/0x220 drivers/base/core.c:247
 [<ffffffff81ab309c>] kobject_cleanup lib/kobject.c:643 [inline]
 [<ffffffff81ab309c>] kobject_release lib/kobject.c:672 [inline]
 [<ffffffff81ab309c>] kref_sub include/linux/kref.h:73 [inline]
 [<ffffffff81ab309c>] kref_put include/linux/kref.h:98 [inline]
 [<ffffffff81ab309c>] kobject_put+0x14c/0x260 lib/kobject.c:689
 [<ffffffff81a7e013>] put_disk+0x23/0x30 block/genhd.c:1346
 [<ffffffff8154ef2c>] __blkdev_get+0x66c/0xdf0 fs/block_dev.c:1290
 [<ffffffff81551938>] blkdev_get+0x2e8/0x920 fs/block_dev.c:1353
 [<ffffffff8155219a>] blkdev_open+0x1aa/0x250 fs/block_dev.c:1508
 [<ffffffff8149154f>] do_dentry_open+0x38f/0xbd0 fs/open.c:749
 [<ffffffff81494d3b>] vfs_open+0x10b/0x210 fs/open.c:862
 [<ffffffff814c5ddf>] do_last fs/namei.c:3269 [inline]
 [<ffffffff814c5ddf>] path_openat+0x136f/0x4470 fs/namei.c:3406
 [<ffffffff814ccab1>] do_filp_open+0x1a1/0x270 fs/namei.c:3440
 [<ffffffff81495668>] do_sys_open+0x2f8/0x600 fs/open.c:1038
 [<ffffffff81599c4a>] C_SYSC_open fs/compat.c:1092 [inline]
 [<ffffffff81599c4a>] compat_SyS_open+0x2a/0x40 fs/compat.c:1090
 [<ffffffff8100603d>] do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
 [<ffffffff8100603d>] do_fast_syscall_32+0x32d/0xa90 arch/x86/entry/common.c:397
 [<ffffffff8271a350>] sysenter_flags_fixed+0xd/0x1a

The buggy address belongs to the object at ffff8801cf099100
 which belongs to the cache kmalloc-2048 of size 2048
audit_printk_skb: 9 callbacks suppressed
audit: type=1400 audit(1551883182.036:278): avc:  denied  { create } for  pid=25111 comm="syz-executor.2" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_generic_socket permissive=0
audit: type=1400 audit(1551883182.036:279): avc:  denied  { create } for  pid=25111 comm="syz-executor.2" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_generic_socket permissive=0
audit: type=1400 audit(1551883182.036:280): avc:  denied  { create } for  pid=25111 comm="syz-executor.2" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_generic_socket permissive=0
The buggy address is located 1384 bytes inside of
 2048-byte region [ffff8801cf099100, ffff8801cf099900)
The buggy address belongs to the page:
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory accessgeneral protection fault: 0000 [#1] PREEMPT SMP KASAN
Modules linked in:
CPU: 1 PID: 25124 Comm: syz-executor.5 Not tainted 4.4.174+ #17
task: ffff8801d11f17c0 task.stack: ffff8801c4060000
RIP: 0010:[<ffffffff81abe481>]  [<ffffffff81abe481>] __rb_insert lib/rbtree.c:118 [inline]
RIP: 0010:[<ffffffff81abe481>]  [<ffffffff81abe481>] rb_insert_color+0x71/0x9d0 lib/rbtree.c:420
RSP: 0018:ffff8801c4067a78  EFLAGS: 00010006
RAX: 0800000000000811 RBX: ffffea00073c2600 RCX: 1ffffd4000e784c1
RDX: 1ffff1003880cfa9 RSI: ffff8801db719390 RDI: ffff8801c4067d48
RBP: ffff8801c4067ab8 R08: ffffffff840fa408 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000000 R12: 4000000000004080
R13: ffff8801c4067d48 R14: dffffc0000000000 R15: 4000000000004088
FS:  0000000000000000(0000) GS:ffff8801db700000(0063) knlGS:0000000009ed2900
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 00000000f5569db0 CR3: 00000001d0560000 CR4: 00000000001606b0
Stack:
 ffffffff81b0abec ffffffff82fb8bc0 0000000000000001 ffff8801db719390
 ffff8801c4067d48 dffffc0000000000 0000008af91778ee ffffea00073c2608
 ffff8801c4067af8 ffffffff81ac9ff8 ffff8801db719390 ffff8801db719380
Call Trace:
 [<ffffffff81ac9ff8>] timerqueue_add+0x1a8/0x320 lib/timerqueue.c:57
 [<ffffffff8125e6ac>] enqueue_hrtimer+0x15c/0x450 kernel/time/hrtimer.c:893
 [<ffffffff81260c4f>] hrtimer_start_range_ns+0x57f/0x1450 kernel/time/hrtimer.c:1013
 [<ffffffff827162b4>] hrtimer_start_expires include/linux/hrtimer.h:407 [inline]
 [<ffffffff827162b4>] do_nanosleep+0x174/0x4c0 kernel/time/hrtimer.c:1500
 [<ffffffff8126373e>] hrtimer_nanosleep+0x20e/0x540 kernel/time/hrtimer.c:1572
 [<ffffffff812b2ce3>] C_SYSC_nanosleep kernel/compat.c:254 [inline]
 [<ffffffff812b2ce3>] compat_SyS_nanosleep+0x173/0x2f0 kernel/compat.c:239
 [<ffffffff8100603d>] do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
 [<ffffffff8100603d>] do_fast_syscall_32+0x32d/0xa90 arch/x86/entry/common.c:397
 [<ffffffff8271a350>] sysenter_flags_fixed+0xd/0x1a
Code: 48 89 d8 48 c1 e8 03 42 80 3c 30 00 0f 85 d0 05 00 00 4c 8b 23 41 f6 c4 01 0f 85 7f 01 00 00 4d 8d 7c 24 08 4c 89 f8 48 c1 e8 03 <42> 80 3c 30 00 0f 85 c1 05 00 00 49 8b 7c 24 08 48 39 df 0f 84 
RIP  [<ffffffff81abe481>] __rb_insert lib/rbtree.c:118 [inline]
RIP  [<ffffffff81abe481>] rb_insert_color+0x71/0x9d0 lib/rbtree.c:420
 RSP <ffff8801c4067a78>
---[ end trace e9f1f49bf825dbe2 ]---