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BUG: KASAN: use-after-free in __lock_acquire+0x3829/0x5020 kernel/locking/lockdep.c:3314
Read of size 8 at addr ffff8801c7803a98 by task kworker/1:0/19

CPU: 1 PID: 19 Comm: kworker/1:0 Not tainted 4.18.0-rc6+ #168
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events p9_poll_workfn
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+0x242/0x2fe mm/kasan/report.c:412
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
 __lock_acquire+0x3829/0x5020 kernel/locking/lockdep.c:3314
 lock_acquire+0x1e4/0x540 kernel/locking/lockdep.c:3924
 __mutex_lock_common kernel/locking/mutex.c:757 [inline]
 __mutex_lock+0x176/0x1820 kernel/locking/mutex.c:894
 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:909
 ep_scan_ready_list+0xb77/0xf50 fs/eventpoll.c:681
 ep_eventpoll_poll+0x192/0x200 fs/eventpoll.c:937
 vfs_poll include/linux/poll.h:86 [inline]
 p9_fd_poll+0x118/0x2b0 net/9p/trans_fd.c:246
 p9_poll_mux net/9p/trans_fd.c:617 [inline]
 p9_poll_workfn+0x463/0x6d0 net/9p/trans_fd.c:1107
 process_one_work+0xc73/0x1ba0 kernel/workqueue.c:2153
 worker_thread+0x189/0x13c0 kernel/workqueue.c:2296
 kthread+0x345/0x410 kernel/kthread.c:246
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412

Allocated by task 6677:
 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
 kmem_cache_alloc_trace+0x152/0x780 mm/slab.c:3620
 kmalloc include/linux/slab.h:513 [inline]
 kzalloc include/linux/slab.h:707 [inline]
 ep_alloc fs/eventpoll.c:1016 [inline]
 do_epoll_create+0x170/0x5c0 fs/eventpoll.c:1952
 __do_sys_epoll_create1 fs/eventpoll.c:1983 [inline]
 __se_sys_epoll_create1 fs/eventpoll.c:1981 [inline]
 __x64_sys_epoll_create1+0x31/0x40 fs/eventpoll.c:1981
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 6677:
 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]
 kfree+0xd9/0x260 mm/slab.c:3813
 ep_free+0x273/0x310 fs/eventpoll.c:856
 ep_eventpoll_release+0x44/0x60 fs/eventpoll.c:864
 __fput+0x355/0x8b0 fs/file_table.c:209
 ____fput+0x15/0x20 fs/file_table.c:243
 task_work_run+0x1ec/0x2a0 kernel/task_work.c:113
 get_signal+0x1559/0x1970 kernel/signal.c:2298
 do_signal+0x9c/0x21c0 arch/x86/kernel/signal.c:816
 exit_to_usermode_loop+0x2e0/0x370 arch/x86/entry/common.c:162
 prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
 do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8801c7803a00
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 152 bytes inside of
 512-byte region [ffff8801c7803a00, ffff8801c7803c00)
The buggy address belongs to the page:
page:ffffea00071e00c0 count:1 mapcount:0 mapping:ffff8801dac00940 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffffea0006f19008 ffffea00076573c8 ffff8801dac00940
raw: 0000000000000000 ffff8801c7803000 0000000100000006 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801c7803980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801c7803a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801c7803a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff8801c7803b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801c7803b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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