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BUG: KASAN: slab-use-after-free in hci_uart_write_work+0x82d/0x960 drivers/bluetooth/hci_ldisc.c:165
Read of size 4 at addr ffff888025f5f0b0 by task kworker/0:4/6023

CPU: 0 UID: 0 PID: 6023 Comm: kworker/0:4 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Workqueue: events hci_uart_write_work
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xcd/0x630 mm/kasan/report.c:482
 kasan_report+0xe0/0x110 mm/kasan/report.c:595
 hci_uart_write_work+0x82d/0x960 drivers/bluetooth/hci_ldisc.c:165
 process_one_work+0x9ba/0x1b20 kernel/workqueue.c:3257
 process_scheduled_works kernel/workqueue.c:3340 [inline]
 worker_thread+0x6c8/0xf10 kernel/workqueue.c:3421
 kthread+0x3c5/0x780 kernel/kthread.c:463
 ret_from_fork+0x983/0xb10 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>

Allocated by task 6821:
 kasan_save_stack+0x33/0x60 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 unpoison_slab_object mm/kasan/common.c:340 [inline]
 __kasan_slab_alloc+0x89/0x90 mm/kasan/common.c:366
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4953 [inline]
 slab_alloc_node mm/slub.c:5263 [inline]
 kmem_cache_alloc_node_noprof+0x298/0x800 mm/slub.c:5315
 __alloc_skb+0x156/0x410 net/core/skbuff.c:679
 alloc_skb include/linux/skbuff.h:1383 [inline]
 bcsp_prepare_pkt+0xe0/0xae0 drivers/bluetooth/hci_bcsp.c:218
 bcsp_dequeue+0x237/0x4b0 drivers/bluetooth/hci_bcsp.c:308
 hci_uart_dequeue drivers/bluetooth/hci_ldisc.c:107 [inline]
 hci_uart_write_work+0x4e3/0x960 drivers/bluetooth/hci_ldisc.c:161
 process_one_work+0x9ba/0x1b20 kernel/workqueue.c:3257
 process_scheduled_works kernel/workqueue.c:3340 [inline]
 worker_thread+0x6c8/0xf10 kernel/workqueue.c:3421
 kthread+0x3c5/0x780 kernel/kthread.c:463
 ret_from_fork+0x983/0xb10 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

The buggy address belongs to the object at ffff888025f5f040
 which belongs to the cache skbuff_head_cache of size 240
The buggy address is located 112 bytes inside of
 freed 240-byte region [ffff888025f5f040, ffff888025f5f130)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x25f5e
head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff8880132f1c01
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff888040ebc8c0 ffffea00004d9a00 dead000000000002
raw: 0000000000000000 0000000000190019 00000000f5000000 ffff8880132f1c01
head: 00fff00000000040 ffff888040ebc8c0 ffffea00004d9a00 dead000000000002
head: 0000000000000000 0000000000190019 00000000f5000000 ffff8880132f1c01
head: 00fff00000000001 ffffea000097d781 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000002
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Unmovable, gfp_mask 0x52820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 10987, tgid 10980 (syz.2.1059), ts 430807251206, free_ts 159910858891
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1af/0x220 mm/page_alloc.c:1857
 prep_new_page mm/page_alloc.c:1865 [inline]
 get_page_from_freelist+0xd0b/0x31a0 mm/page_alloc.c:3915
 __alloc_pages_slowpath mm/page_alloc.c:4741 [inline]
 __alloc_frozen_pages_noprof+0x6d7/0x2430 mm/page_alloc.c:5223
 alloc_pages_mpol+0x1fb/0x550 mm/mempolicy.c:2486
 alloc_slab_page mm/slub.c:3075 [inline]
 allocate_slab mm/slub.c:3248 [inline]
 new_slab+0x2c3/0x430 mm/slub.c:3302
 ___slab_alloc+0xe18/0x1c90 mm/slub.c:4656
 __slab_alloc.constprop.0+0x63/0x110 mm/slub.c:4779
 __slab_alloc_node mm/slub.c:4855 [inline]
 slab_alloc_node mm/slub.c:5251 [inline]
 kmem_cache_alloc_noprof+0x44d/0x770 mm/slub.c:5270
 skb_clone+0x190/0x3f0 net/core/skbuff.c:2087
 __skb_tstamp_tx+0x7aa/0xbb0 net/core/skbuff.c:5677
 skb_tx_timestamp include/linux/skbuff.h:4711 [inline]
 tun_net_xmit+0x1108/0x1940 drivers/net/tun.c:1054
 __netdev_start_xmit include/linux/netdevice.h:5273 [inline]
 netdev_start_xmit include/linux/netdevice.h:5282 [inline]
 xmit_one net/core/dev.c:3853 [inline]
 dev_hard_start_xmit+0x97/0x6e0 net/core/dev.c:3869
 sch_direct_xmit+0x1b2/0xcd0 net/sched/sch_generic.c:347
 __dev_xmit_skb net/core/dev.c:4169 [inline]
 __dev_queue_xmit+0x14a6/0x46b0 net/core/dev.c:4785
 dev_queue_xmit include/linux/netdevice.h:3381 [inline]
 neigh_hh_output include/net/neighbour.h:540 [inline]
 neigh_output include/net/neighbour.h:554 [inline]
 ip_finish_output2+0xc38/0x21a0 net/ipv4/ip_output.c:237
 __ip_finish_output.part.0+0x1b4/0x350 net/ipv4/ip_output.c:315
page last free pid 1160 tgid 1160 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1406 [inline]
 __free_frozen_pages+0x7df/0x1170 mm/page_alloc.c:2943
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x4c/0xf0 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x195/0x1e0 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x69/0x90 mm/kasan/common.c:350
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4953 [inline]
 slab_alloc_node mm/slub.c:5263 [inline]
 kmem_cache_alloc_noprof+0x25e/0x770 mm/slub.c:5270
 __proc_create+0x2c8/0x8d0 fs/proc/generic.c:452
 _proc_mkdir+0xb9/0x210 fs/proc/generic.c:515
 proc_net_mkdir include/linux/proc_fs.h:236 [inline]
 afs_proc_cell_setup+0xbe/0x200 fs/afs/proc.c:696
 afs_activate_cell fs/afs/cell.c:728 [inline]
 afs_manage_cell fs/afs/cell.c:819 [inline]
 afs_manage_cell_work+0x8a3/0x1960 fs/afs/cell.c:884
 process_one_work+0x9ba/0x1b20 kernel/workqueue.c:3257
 process_scheduled_works kernel/workqueue.c:3340 [inline]
 worker_thread+0x6c8/0xf10 kernel/workqueue.c:3421
 kthread+0x3c5/0x780 kernel/kthread.c:463
 ret_from_fork+0x983/0xb10 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

Memory state around the buggy address:
 ffff888025f5ef80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc
 ffff888025f5f000: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
>ffff888025f5f080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                     ^
 ffff888025f5f100: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc
 ffff888025f5f180: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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