==================================================================
BUG: KASAN: use-after-free in disk_unblock_events+0x55/0x60 block/genhd.c:1543
Read of size 8 at addr ffff8800b613d1e8 by task syz-executor552/2132

CPU: 1 PID: 2132 Comm: syz-executor552 Not tainted 4.4.174+ #17
 0000000000000000 c13e9a7ffcea12d9 ffff8801d41ff6c0 ffffffff81aad1a1
 0000000000000000 ffffea0002d84e00 ffff8800b613d1e8 0000000000000008
 0000000000000000 ffff8801d41ff6f8 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 2132:
 [<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
 [<ffffffff8159b2c3>] C_SYSC_ioctl fs/compat_ioctl.c:1592 [inline]
 [<ffffffff8159b2c3>] compat_SyS_ioctl+0x403/0x2210 fs/compat_ioctl.c:1544
 [<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 2132:
 [<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 ffff8800b613cc80
 which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 1384 bytes inside of
 2048-byte region [ffff8800b613cc80, ffff8800b613d480)
The buggy address belongs to the page:
BUG: unable to handle kernel paging request at fffff940005b09c0
IP: [<ffffffff81add4d9>] memset_erms+0x9/0x10 arch/x86/lib/memset_64.S:62
PGD 330c067 PUD 330b063 PMD 330a063 PTE 800000000330d161
Oops: 0003 [#1] PREEMPT SMP KASAN
Modules linked in:
CPU: 0 PID: 567 Comm: udevd Not tainted 4.4.174+ #17
task: ffff8801d5688000 task.stack: ffff8801d5690000
RIP: 0010:[<ffffffff81add4d9>]  [<ffffffff81add4d9>] memset_erms+0x9/0x10 arch/x86/lib/memset_64.S:62
RSP: 0018:ffff8801d5697b50  EFLAGS: 00010202
RAX: 1ffffd40005b0900 RBX: fffff940005b09c4 RCX: 0000000000000004
RDX: 0000000000000004 RSI: 0000000000000000 RDI: fffff940005b09c0
RBP: ffff8801d5697b68 R08: 1ffff1003a8f11c0 R09: fffff940005b09c0
R10: ffffed003a8f11c3 R11: ffff8801d4788e1f R12: 0000000000000020
R13: ffffea0002d84e00 R14: ffffea0002d84e1f R15: ffff8801da401a00
FS:  00007f1d80ea37a0(0000) GS:ffff8801db600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: fffff940005b09c0 CR3: 00000001d5679000 CR4: 00000000001606b0
Stack:
 ffffffff81484025 ffffea0002d84e20 00000000024000c0 ffff8801d5697ba8
 ffffffff8148412c ffffea0002d84e1f 0000000000004080 ffff8801da401a00
 00000000024000c0 0000000000000011 ffffea0002d84e00 ffff8801d5697bb8
Call Trace:
 [<ffffffff8148412c>] kasan_kmalloc+0x4c/0xd0 mm/kasan/kasan.c:611
 [<ffffffff8148475f>] kasan_slab_alloc+0xf/0x20 mm/kasan/kasan.c:554
 [<ffffffff814804df>] slab_post_alloc_hook mm/slub.c:1349 [inline]
 [<ffffffff814804df>] slab_alloc_node mm/slub.c:2615 [inline]
 [<ffffffff814804df>] slab_alloc mm/slub.c:2623 [inline]
 [<ffffffff814804df>] __kmalloc+0xff/0x330 mm/slub.c:3609
 [<ffffffff813ff352>] kmalloc include/linux/slab.h:481 [inline]
 [<ffffffff813ff352>] shmem_initxattrs+0x82/0x1f0 mm/shmem.c:2540
 [<ffffffff8194b399>] security_inode_init_security security/security.c:393 [inline]
 [<ffffffff8194b399>] security_inode_init_security+0x279/0x370 security/security.c:366
 [<ffffffff81406c6e>] shmem_symlink+0xee/0x670 mm/shmem.c:2453
 [<ffffffff814c994f>] vfs_symlink2 fs/namei.c:4040 [inline]
 [<ffffffff814c994f>] vfs_symlink2+0x1ef/0x3c0 fs/namei.c:4026
 [<ffffffff814cd78e>] SYSC_symlinkat fs/namei.c:4073 [inline]
 [<ffffffff814cd78e>] SyS_symlinkat+0x14e/0x240 fs/namei.c:4053
 [<ffffffff814cd8a3>] SYSC_symlink fs/namei.c:4086 [inline]
 [<ffffffff814cd8a3>] SyS_symlink+0x23/0x30 fs/namei.c:4084
 [<ffffffff82718ba1>] entry_SYSCALL_64_fastpath+0x1e/0x9a
Code: 48 c1 e9 03 40 0f b6 f6 48 b8 01 01 01 01 01 01 01 01 48 0f af c6 f3 48 ab 89 d1 f3 aa 4c 89 c8 c3 90 49 89 f9 40 88 f0 48 89 d1 <f3> aa 4c 89 c8 c3 90 49 89 fa 40 0f b6 ce 48 b8 01 01 01 01 01 
RIP  [<ffffffff81add4d9>] memset_erms+0x9/0x10 arch/x86/lib/memset_64.S:61
 RSP <ffff8801d5697b50>
CR2: fffff940005b09c0
---[ end trace 7332debb7d6ef803 ]---