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BUG: KASAN: use-after-free in timer_is_static_object+0x7a/0x90 kernel/time/timer.c:619
Read of size 8 at addr ffff88805e404380 by task syz-executor.0/12991
CPU: 0 PID: 12991 Comm: syz-executor.0 Not tainted 5.8.0-rc6-next-20200724-syzkaller #0
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+0x18f/0x20d lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xae/0x497 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
 timer_is_static_object+0x7a/0x90 kernel/time/timer.c:619
 debug_object_assert_init lib/debugobjects.c:866 [inline]
 debug_object_assert_init+0x1df/0x2e0 lib/debugobjects.c:841
 debug_timer_assert_init kernel/time/timer.c:736 [inline]
 debug_assert_init kernel/time/timer.c:781 [inline]
 del_timer+0x6d/0x110 kernel/time/timer.c:1207
 try_to_grab_pending kernel/workqueue.c:1249 [inline]
 __cancel_work_timer+0x12d/0x700 kernel/workqueue.c:3092
 ceph_mdsc_stop fs/ceph/mds_client.c:4660 [inline]
 ceph_mdsc_destroy+0x50/0x140 fs/ceph/mds_client.c:4679
 destroy_fs_client+0x13/0x200 fs/ceph/super.c:720
 ceph_get_tree+0x9e5/0x1660 fs/ceph/super.c:1110
 vfs_get_tree+0x89/0x2f0 fs/super.c:1558
 do_new_mount fs/namespace.c:2912 [inline]
 do_mount+0x14f6/0x1e20 fs/namespace.c:3238
 __do_sys_mount fs/namespace.c:3448 [inline]
 __se_sys_mount fs/namespace.c:3425 [inline]
 __x64_sys_mount+0x18f/0x230 fs/namespace.c:3425
 do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45c369
Code: Bad RIP value.
RSP: 002b:00007fea7ff60c78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 000000000001fb40 RCX: 000000000045c369
RDX: 0000000020000040 RSI: 00000000200000c0 RDI: 0000000020000480
RBP: 000000000078bf50 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000078bf0c
R13: 00007ffc4ffb483f R14: 00007fea7ff619c0 R15: 000000000078bf0c
Allocated by task 12991:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
 kasan_set_track mm/kasan/common.c:56 [inline]
 __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:461
 kmem_cache_alloc_trace+0x16e/0x2c0 mm/slab.c:3550
 kmalloc include/linux/slab.h:554 [inline]
 kzalloc include/linux/slab.h:666 [inline]
 ceph_mdsc_init+0x47/0xf10 fs/ceph/mds_client.c:4351
 ceph_get_tree+0x4fe/0x1660 fs/ceph/super.c:1063
 vfs_get_tree+0x89/0x2f0 fs/super.c:1558
 do_new_mount fs/namespace.c:2912 [inline]
 do_mount+0x14f6/0x1e20 fs/namespace.c:3238
 __do_sys_mount fs/namespace.c:3448 [inline]
 __se_sys_mount fs/namespace.c:3425 [inline]
 __x64_sys_mount+0x18f/0x230 fs/namespace.c:3425
 do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
Freed by task 12991:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
 kasan_set_track+0x1c/0x30 mm/kasan/common.c:56
 kasan_set_free_info+0x1b/0x30 mm/kasan/generic.c:355
 __kasan_slab_free+0xd8/0x120 mm/kasan/common.c:422
 __cache_free mm/slab.c:3418 [inline]
 kfree+0x103/0x2c0 mm/slab.c:3756
 ceph_mdsc_init+0xc64/0xf10 fs/ceph/mds_client.c:4422
 ceph_get_tree+0x4fe/0x1660 fs/ceph/super.c:1063
 vfs_get_tree+0x89/0x2f0 fs/super.c:1558
 do_new_mount fs/namespace.c:2912 [inline]
 do_mount+0x14f6/0x1e20 fs/namespace.c:3238
 __do_sys_mount fs/namespace.c:3448 [inline]
 __se_sys_mount fs/namespace.c:3425 [inline]
 __x64_sys_mount+0x18f/0x230 fs/namespace.c:3425
 do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
The buggy address belongs to the object at ffff88805e404000
 which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 896 bytes inside of
 4096-byte region [ffff88805e404000, ffff88805e405000)
The buggy address belongs to the page:
page:0000000086268fb2 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x5e404
head:0000000086268fb2 order:1 compound_mapcount:0
flags: 0xfffe0000010200(slab|head)
raw: 00fffe0000010200 ffffea0000d2d888 ffffea0001790188 ffff8880aa000900
raw: 0000000000000000 ffff88805e404000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
 ffff88805e404280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88805e404300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88805e404380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff88805e404400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88805e404480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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