==================================================================
BUG: KASAN: use-after-free in disk_unblock_events+0x55/0x60 block/genhd.c:1543
Read of size 8 at addr ffff8801cf3a8568 by task syz-executor573/2089

CPU: 0 PID: 2089 Comm: syz-executor573 Not tainted 4.4.174+ #4
 0000000000000000 296d3e421fc83d37 ffff8800b658f730 ffffffff81aad1a1
 0000000000000000 ffffea00073cea00 ffff8801cf3a8568 0000000000000008
 0000000000000000 ffff8800b658f768 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
 [<ffffffff8149599d>] SYSC_open fs/open.c:1056 [inline]
 [<ffffffff8149599d>] SyS_open+0x2d/0x40 fs/open.c:1051
 [<ffffffff82718ba1>] entry_SYSCALL_64_fastpath+0x1e/0x9a

Allocated by task 2089:
 [<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
 [<ffffffff81d440a8>] loop_control_ioctl+0x138/0x2f0 drivers/block/loop.c:1988
 [<ffffffff814d23f7>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff814d23f7>] file_ioctl fs/ioctl.c:470 [inline]
 [<ffffffff814d23f7>] do_vfs_ioctl+0x6e7/0xfa0 fs/ioctl.c:605
 [<ffffffff814d2d3f>] SYSC_ioctl fs/ioctl.c:622 [inline]
 [<ffffffff814d2d3f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:613
 [<ffffffff82718ba1>] entry_SYSCALL_64_fastpath+0x1e/0x9a

Freed by task 2089:
 [<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
 [<ffffffff8149599d>] SYSC_open fs/open.c:1056 [inline]
 [<ffffffff8149599d>] SyS_open+0x2d/0x40 fs/open.c:1051
 [<ffffffff82718ba1>] entry_SYSCALL_64_fastpath+0x1e/0x9a

The buggy address belongs to the object at ffff8801cf3a8000
 which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 1384 bytes inside of
 2048-byte region [ffff8801cf3a8000, ffff8801cf3a8800)
The buggy address belongs to the page:
BUG: unable to handle kernel paging request at ffffeb88001cf3a0
IP: [<ffffffff8148513a>] __read_once_size include/linux/compiler.h:218 [inline]
IP: [<ffffffff8148513a>] compound_head include/linux/page-flags.h:415 [inline]
IP: [<ffffffff8148513a>] virt_to_head_page include/linux/mm.h:523 [inline]
IP: [<ffffffff8148513a>] qlink_to_cache mm/kasan/quarantine.c:127 [inline]
IP: [<ffffffff8148513a>] qlist_free_all+0x7a/0xc0 mm/kasan/quarantine.c:163
PGD 0 
Oops: 0000 [#1] PREEMPT SMP KASAN
Modules linked in:
CPU: 1 PID: 2076 Comm: syz-executor573 Not tainted 4.4.174+ #4
task: ffff8801d4ed97c0 task.stack: ffff8800b6af0000
RIP: 0010:[<ffffffff8148513a>]  [<ffffffff8148513a>] __read_once_size include/linux/compiler.h:218 [inline]
RIP: 0010:[<ffffffff8148513a>]  [<ffffffff8148513a>] compound_head include/linux/page-flags.h:415 [inline]
RIP: 0010:[<ffffffff8148513a>]  [<ffffffff8148513a>] virt_to_head_page include/linux/mm.h:523 [inline]
RIP: 0010:[<ffffffff8148513a>]  [<ffffffff8148513a>] qlink_to_cache mm/kasan/quarantine.c:127 [inline]
RIP: 0010:[<ffffffff8148513a>]  [<ffffffff8148513a>] qlist_free_all+0x7a/0xc0 mm/kasan/quarantine.c:163
RSP: 0000:ffff8800b6af7860  EFLAGS: 00010282
RAX: ffffeb88001cf380 RBX: 0000000000000000 RCX: 000000018080005f
RDX: 000077ff80000000 RSI: ffffea00073cea00 RDI: 0000000000000000
RBP: ffff8800b6af7888 R08: 0000000000000001 R09: ffffffff814850f1
R10: ffffea0002d944c0 R11: 0000000000000000 R12: ffff8800b6af78a0
R13: 0000000080000000 R14: ffffea0000000000 R15: ffffea00073cea00
FS:  00000000024d0880(0063) GS:ffff8801db700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffeb88001cf3a0 CR3: 00000000b68a6000 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff8801d4ed97c0 0000000000000000 ffff8800b6af78a0 ffffffff81139e98
 ffff8801da488640 ffff8800b6af78d0 ffffffff8148558f ffffffff81485495
 ffff8801d3e58000 ffff8800b641c400 00000000001010a0 7d276a79957381f4
Call Trace:
 [<ffffffff8148558f>] quarantine_reduce+0x18f/0x1d0 mm/kasan/quarantine.c:259
 [<ffffffff81484180>] kasan_kmalloc+0xa0/0xd0 mm/kasan/kasan.c:601
 [<ffffffff8148475f>] kasan_slab_alloc+0xf/0x20 mm/kasan/kasan.c:554
 [<ffffffff8147fe9c>] slab_post_alloc_hook mm/slub.c:1349 [inline]
 [<ffffffff8147fe9c>] slab_alloc_node mm/slub.c:2615 [inline]
 [<ffffffff8147fe9c>] slab_alloc mm/slub.c:2623 [inline]
 [<ffffffff8147fe9c>] kmem_cache_alloc+0xdc/0x2c0 mm/slub.c:2628
 [<ffffffff81139e98>] prepare_creds+0x28/0x2b0 kernel/cred.c:251
 [<ffffffff815bdebf>] do_coredump+0x30f/0x29d0 fs/coredump.c:547
 [<ffffffff81100b59>] get_signal+0x5d9/0x1570 kernel/signal.c:2315
 [<ffffffff8100bd4c>] do_signal+0x9c/0x1840 arch/x86/kernel/signal.c:712
 [<ffffffff81003da7>] exit_to_usermode_loop+0x127/0x170 arch/x86/entry/common.c:184
 [<ffffffff810053ba>] prepare_exit_to_usermode+0x15a/0x1e0 arch/x86/entry/common.c:221
 [<ffffffff82719745>] retint_user+0x8/0x3c
Code: 4c 89 fe 48 85 db 48 89 df 75 d7 48 89 f0 4c 01 e8 72 52 48 ba 00 00 00 80 ff 77 00 00 48 01 d0 48 c1 e8 0c 48 c1 e0 06 4c 01 f0 <48> 8b 50 20 48 8d 4a ff 83 e2 01 48 0f 45 c1 48 8b 78 30 eb a2 
RIP  [<ffffffff8148513a>] virt_to_head_page include/linux/mm.h:521 [inline]
RIP  [<ffffffff8148513a>] qlink_to_cache mm/kasan/quarantine.c:127 [inline]
RIP  [<ffffffff8148513a>] qlist_free_all+0x7a/0xc0 mm/kasan/quarantine.c:163
 RSP <ffff8800b6af7860>
CR2: ffffeb88001cf3a0
---[ end trace dbaf3d1cc2c5a2c7 ]---