BUG: KASAN: use-after-free in __hlist_del include/linux/list.h:826 [inline]
BUG: KASAN: use-after-free in hlist_del_rcu include/linux/rculist.h:487 [inline]
BUG: KASAN: use-after-free in afs_deactivate_cell+0x165/0x1a0 fs/afs/cell.c:647
Read of size 8 at addr ffff888027507080 by task kworker/3:7/1064

CPU: 3 PID: 1064 Comm: kworker/3:7 Not tainted 5.9.0-rc6-syzkaller #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014
Workqueue: afs afs_manage_cell
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x198/0x1fd 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
 __hlist_del include/linux/list.h:826 [inline]
 hlist_del_rcu include/linux/rculist.h:487 [inline]
 afs_deactivate_cell+0x165/0x1a0 fs/afs/cell.c:647
 afs_manage_cell+0x326/0x11c0 fs/afs/cell.c:721
 process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
 kthread+0x3b5/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

Allocated by task 2179:
 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+0x174/0x300 mm/slab.c:3550
 kmalloc include/linux/slab.h:554 [inline]
 kzalloc include/linux/slab.h:666 [inline]
 afs_alloc_cell fs/afs/cell.c:151 [inline]
 afs_lookup_cell+0x5c8/0x1440 fs/afs/cell.c:262
 afs_parse_source fs/afs/super.c:290 [inline]
 afs_parse_param+0x404/0x8c0 fs/afs/super.c:326
 vfs_parse_fs_param fs/fs_context.c:117 [inline]
 vfs_parse_fs_param+0x203/0x550 fs/fs_context.c:98
 vfs_parse_fs_string+0xe6/0x150 fs/fs_context.c:161
 generic_parse_monolithic+0x16f/0x1f0 fs/fs_context.c:201
 do_new_mount fs/namespace.c:2871 [inline]
 path_mount+0x133f/0x20a0 fs/namespace.c:3192
 do_mount+0xf3/0x110 fs/namespace.c:3205
 __do_compat_sys_mount fs/compat.c:122 [inline]
 __se_compat_sys_mount fs/compat.c:89 [inline]
 __ia32_compat_sys_mount+0x193/0x710 fs/compat.c:89
 do_syscall_32_irqs_on arch/x86/entry/common.c:78 [inline]
 __do_fast_syscall_32+0x60/0x90 arch/x86/entry/common.c:137
 do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:160
 entry_SYSENTER_compat_after_hwframe+0x4d/0x5c

Freed by task 27:
 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+0x10e/0x2b0 mm/slab.c:3756
 rcu_do_batch kernel/rcu/tree.c:2428 [inline]
 rcu_core+0x5ca/0x1130 kernel/rcu/tree.c:2656
 __do_softirq+0x1f8/0xb23 kernel/softirq.c:298

Last call_rcu():
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
 kasan_record_aux_stack+0x82/0xb0 mm/kasan/generic.c:346
 __call_rcu kernel/rcu/tree.c:2894 [inline]
 call_rcu+0x15e/0x7c0 kernel/rcu/tree.c:2968
 afs_manage_cell+0x250/0x11c0 fs/afs/cell.c:751
 process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
 kthread+0x3b5/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

The buggy address belongs to the object at ffff888027507000
 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 128 bytes inside of
 1024-byte region [ffff888027507000, ffff888027507400)
The buggy address belongs to the page:
page:000000009e3ad316 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x27507
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea00008e5e48 ffffea0000868988 ffff88802c840700
raw: 0000000000000000 ffff888027507000 0000000100000002 ffff8880271cadc1
page dumped because: kasan: bad access detected
page->mem_cgroup:ffff8880271cadc1

Memory state around the buggy address:
 ffff888027506f80: fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888027507000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888027507080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff888027507100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888027507180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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