syzbot

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BUG: KASAN: slab-use-after-free in instrument_atomic_read include/linux/instrumented.h:68 [inline]
BUG: KASAN: slab-use-after-free in atomic_long_read include/linux/atomic/atomic-instrumented.h:3188 [inline]
BUG: KASAN: slab-use-after-free in __mutex_unlock_slowpath+0xd4/0x700 kernel/locking/mutex.c:916
Read of size 8 at addr ffff8880286d5ad0 by task kworker/1:3/21668

CPU: 1 UID: 0 PID: 21668 Comm: kworker/1:3 Not tainted 6.15.0-rc7-syzkaller-00002-gb36ddb9210e6 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: events l2cap_chan_timeout
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:408 [inline]
 print_report+0xb4/0x290 mm/kasan/report.c:521
 kasan_report+0x118/0x150 mm/kasan/report.c:634
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x29a/0x2b0 mm/kasan/generic.c:189
 instrument_atomic_read include/linux/instrumented.h:68 [inline]
 atomic_long_read include/linux/atomic/atomic-instrumented.h:3188 [inline]
 __mutex_unlock_slowpath+0xd4/0x700 kernel/locking/mutex.c:916
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0xade/0x17a0 kernel/workqueue.c:3319
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3400
 kthread+0x711/0x8a0 kernel/kthread.c:464
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Allocated by task 23813:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
 poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:394
 kasan_kmalloc include/linux/kasan.h:260 [inline]
 __kmalloc_cache_noprof+0x230/0x3d0 mm/slub.c:4358
 kmalloc_noprof include/linux/slab.h:905 [inline]
 kzalloc_noprof include/linux/slab.h:1039 [inline]
 l2cap_conn_add+0xaa/0x8d0 net/bluetooth/l2cap_core.c:6861
 l2cap_chan_connect+0x6c8/0xe30 net/bluetooth/l2cap_core.c:7052
 bt_6lowpan_connect net/bluetooth/6lowpan.c:900 [inline]
 lowpan_control_write+0x421/0x6c0 net/bluetooth/6lowpan.c:1135
 full_proxy_write+0x15a/0x220 fs/debugfs/file.c:398
 vfs_write+0x27e/0xa90 fs/read_write.c:682
 ksys_write+0x145/0x250 fs/read_write.c:736
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 24276:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:576
 poison_slab_object mm/kasan/common.c:247 [inline]
 __kasan_slab_free+0x62/0x70 mm/kasan/common.c:264
 kasan_slab_free include/linux/kasan.h:233 [inline]
 slab_free_hook mm/slub.c:2380 [inline]
 slab_free mm/slub.c:4642 [inline]
 kfree+0x193/0x440 mm/slub.c:4841
 hci_disconn_cfm include/net/bluetooth/hci_core.h:2068 [inline]
 hci_conn_hash_flush+0x10a/0x230 net/bluetooth/hci_conn.c:2534
 hci_dev_close_sync+0xaef/0x1330 net/bluetooth/hci_sync.c:5225
 hci_dev_do_close net/bluetooth/hci_core.c:483 [inline]
 hci_unregister_dev+0x206/0x500 net/bluetooth/hci_core.c:2678
 vhci_release+0x80/0xd0 drivers/bluetooth/hci_vhci.c:665
 __fput+0x449/0xa70 fs/file_table.c:465
 task_work_run+0x1d4/0x260 kernel/task_work.c:227
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0x8d6/0x2550 kernel/exit.c:953
 do_group_exit+0x21c/0x2d0 kernel/exit.c:1102
 get_signal+0x125e/0x1310 kernel/signal.c:3034
 arch_do_signal_or_restart+0x95/0x780 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0x8b/0x120 kernel/entry/common.c:218
 do_syscall_64+0x103/0x210 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff8880286d5800
 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 720 bytes inside of
 freed 1024-byte region [ffff8880286d5800, ffff8880286d5c00)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x286d0
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801a041dc0 dead000000000100 dead000000000122
raw: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801a041dc0 dead000000000100 dead000000000122
head: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
head: 00fff00000000003 ffffea0000a1b401 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd2820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 10599, tgid 10592 (syz.1.847), ts 489014007001, free_ts 487477546121
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1d8/0x230 mm/page_alloc.c:1714
 prep_new_page mm/page_alloc.c:1722 [inline]
 get_page_from_freelist+0x21c7/0x22a0 mm/page_alloc.c:3684
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:4966
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2301
 alloc_slab_page mm/slub.c:2450 [inline]
 allocate_slab+0x8a/0x3b0 mm/slub.c:2618
 new_slab mm/slub.c:2672 [inline]
 ___slab_alloc+0xbfc/0x1480 mm/slub.c:3858
 __slab_alloc mm/slub.c:3948 [inline]
 __slab_alloc_node mm/slub.c:4023 [inline]
 slab_alloc_node mm/slub.c:4184 [inline]
 __do_kmalloc_node mm/slub.c:4326 [inline]
 __kmalloc_node_track_caller_noprof+0x2f8/0x4e0 mm/slub.c:4346
 kmalloc_reserve+0x136/0x290 net/core/skbuff.c:599
 __alloc_skb+0x142/0x2d0 net/core/skbuff.c:668
 alloc_skb include/linux/skbuff.h:1340 [inline]
 xfrm_alloc_compat+0x1a6/0x16f0 net/xfrm/xfrm_compat.c:348
 xfrm_nlmsg_multicast+0xda/0x1f0 net/xfrm/xfrm_user.c:1548
 xfrm_send_acquire+0x99d/0xee0 net/xfrm/xfrm_user.c:3801
 km_query+0x11c/0x210 net/xfrm/xfrm_state.c:2754
 xfrm_state_find+0x3cc5/0x5520 net/xfrm/xfrm_state.c:1575
 xfrm_tmpl_resolve_one net/xfrm/xfrm_policy.c:2519 [inline]
 xfrm_tmpl_resolve net/xfrm/xfrm_policy.c:2570 [inline]
 xfrm_resolve_and_create_bundle+0x768/0x2f90 net/xfrm/xfrm_policy.c:2868
 xfrm_lookup_with_ifid+0x2a7/0x1a70 net/xfrm/xfrm_policy.c:3202
page last free pid 5188 tgid 5188 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1258 [inline]
 __free_frozen_pages+0xb05/0xcd0 mm/page_alloc.c:2721
 discard_slab mm/slub.c:2716 [inline]
 __put_partials+0x161/0x1c0 mm/slub.c:3185
 put_cpu_partial+0x17c/0x250 mm/slub.c:3260
 __slab_free+0x2f7/0x400 mm/slub.c:4512
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x9a/0x140 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:329
 kasan_slab_alloc include/linux/kasan.h:250 [inline]
 slab_post_alloc_hook mm/slub.c:4147 [inline]
 slab_alloc_node mm/slub.c:4196 [inline]
 kmem_cache_alloc_noprof+0x1c1/0x3c0 mm/slub.c:4203
 getname_flags+0xb8/0x540 fs/namei.c:146
 do_readlinkat+0xbc/0x500 fs/stat.c:567
 __do_sys_readlink fs/stat.c:605 [inline]
 __se_sys_readlink fs/stat.c:602 [inline]
 __x64_sys_readlink+0x7f/0x90 fs/stat.c:602
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff8880286d5980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880286d5a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880286d5a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                 ^
 ffff8880286d5b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880286d5b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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