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BUG: KASAN: use-after-free in fast_dput fs/dcache.c:717 [inline]
BUG: KASAN: use-after-free in dput.part.26+0x634/0x7a0 fs/dcache.c:836
Read of size 4 at addr ffff88016d1dd9e0 by task syz-executor4/17889

CPU: 0 PID: 17889 Comm: syz-executor4 Not tainted 4.18.0-rc3-next-20180706+ #1
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1c9/0x2b4 lib/dump_stack.c:113
 print_address_description+0x6c/0x20b mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report.cold.7+0x242/0x30d mm/kasan/report.c:412
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432
 fast_dput fs/dcache.c:717 [inline]
 dput.part.26+0x634/0x7a0 fs/dcache.c:836
 dput+0x15/0x20 fs/dcache.c:831
 proc_kill_sb+0x125/0x1e0 fs/proc/root.c:198
 deactivate_locked_super+0x97/0x100 fs/super.c:328
 vfs_get_super+0x20f/0x270 fs/super.c:1270
 proc_get_tree+0x88/0xb0 fs/proc/root.c:159
 vfs_get_tree+0x1cb/0x5c0 fs/super.c:1751
 do_new_mount fs/namespace.c:2567 [inline]
 do_mount+0x6c1/0x1fb0 fs/namespace.c:2889
 ksys_mount+0x12d/0x140 fs/namespace.c:3105
 __do_sys_mount fs/namespace.c:3119 [inline]
 __se_sys_mount fs/namespace.c:3116 [inline]
 __x64_sys_mount+0xbe/0x150 fs/namespace.c:3116
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x455ba9
Code: 1d ba fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 eb b9 fb ff c3 66 2e 0f 1f 84 00 00 00 00 
RSP: 002b:00007fb8f7ec8c68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fb8f7ec96d4 RCX: 0000000000455ba9
RDX: 0000000020000540 RSI: 0000000020000500 RDI: 00000000200004c0
RBP: 000000000072bea0 R08: 0000000020000580 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000014
R13: 00000000004c218e R14: 00000000004cfa78 R15: 0000000000000024

Allocated by task 17742:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:490
 kmem_cache_alloc+0x12e/0x760 mm/slab.c:3554
 __d_alloc+0xc8/0xd50 fs/dcache.c:1617
 d_alloc+0x96/0x380 fs/dcache.c:1701
 d_alloc_name+0xbb/0x120 fs/dcache.c:1755
 proc_setup_self+0xe1/0x3af fs/proc/self.c:43
 proc_fill_super+0x37e/0x630 fs/proc/root.c:133
 vfs_get_super+0x15e/0x270 fs/super.c:1268
 proc_get_tree+0x88/0xb0 fs/proc/root.c:159
 vfs_get_tree+0x1cb/0x5c0 fs/super.c:1751
 do_new_mount fs/namespace.c:2567 [inline]
 do_mount+0x6c1/0x1fb0 fs/namespace.c:2889
 ksys_mount+0x12d/0x140 fs/namespace.c:3105
 __do_sys_mount fs/namespace.c:3119 [inline]
 __se_sys_mount fs/namespace.c:3116 [inline]
 __x64_sys_mount+0xbe/0x150 fs/namespace.c:3116
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 0:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
 __cache_free mm/slab.c:3498 [inline]
 kmem_cache_free+0x86/0x2d0 mm/slab.c:3756
 __d_free+0x20/0x30 fs/dcache.c:257
 __rcu_reclaim kernel/rcu/rcu.h:258 [inline]
 rcu_do_batch kernel/rcu/tree.c:2576 [inline]
 invoke_rcu_callbacks kernel/rcu/tree.c:2878 [inline]
 __rcu_process_callbacks kernel/rcu/tree.c:2845 [inline]
 rcu_process_callbacks+0xe01/0x2810 kernel/rcu/tree.c:2862
 __do_softirq+0x2e8/0xb17 kernel/softirq.c:288

The buggy address belongs to the object at ffff88016d1dd9e0
 which belongs to the cache dentry(81:syz4) of size 288
The buggy address is located 0 bytes inside of
 288-byte region [ffff88016d1dd9e0, ffff88016d1ddb00)
The buggy address belongs to the page:
page:ffffea0005b47740 count:1 mapcount:0 mapping:ffff8801ac566e00 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffffea0005b47ec8 ffffea0005b47fc8 ffff8801ac566e00
raw: 0000000000000000 ffff88016d1dd040 000000010000000b ffff8801b5f0cec0
page dumped because: kasan: bad access detected
page->mem_cgroup:ffff8801b5f0cec0

Memory state around the buggy address:
 ffff88016d1dd880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88016d1dd900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88016d1dd980: fb fb fb fb fc fc fc fc fc fc fc fc fb fb fb fb
                                                       ^
 ffff88016d1dda00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88016d1dda80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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