KASAN: slab-use-after-free Read in l2cap_disconn

Kernel	Title	Rank 🛈	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
upstream	KASAN: slab-use-after-free Read in l2cap_disconn_ind bluetooth	19				2	189d	259d	0/29	auto-obsoleted due to no activity on 2025/05/12 10:49
==================================================================
BUG: KASAN: slab-use-after-free in l2cap_disconn_ind+0xbc/0xd0 net/bluetooth/l2cap_core.c:7299
Read of size 1 at addr ffff88807807bab0 by task kworker/u9:5/5827

CPU: 1 UID: 0 PID: 5827 Comm: kworker/u9:5 Not tainted 6.16.0-rc3-syzkaller-00306-gaaf724ed6926 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: hci1 hci_conn_timeout
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:408 [inline]
 print_report+0xcd/0x680 mm/kasan/report.c:521
 kasan_report+0xe0/0x110 mm/kasan/report.c:634
 l2cap_disconn_ind+0xbc/0xd0 net/bluetooth/l2cap_core.c:7299
 hci_proto_disconn_ind include/net/bluetooth/hci_core.h:2032 [inline]
 hci_conn_timeout+0x190/0x210 net/bluetooth/hci_conn.c:580
 process_one_work+0x9cc/0x1b70 kernel/workqueue.c:3238
 process_scheduled_works kernel/workqueue.c:3321 [inline]
 worker_thread+0x6c8/0xf10 kernel/workqueue.c:3402
 kthread+0x3c2/0x780 kernel/kthread.c:464
 ret_from_fork+0x5d4/0x6f0 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Allocated by task 26062:
 kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
 kasan_save_track+0x14/0x30 mm/kasan/common.c:68
 poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
 __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:394
 kmalloc_noprof include/linux/slab.h:905 [inline]
 kzalloc_noprof include/linux/slab.h:1039 [inline]
 l2cap_conn_add.part.0+0x60/0xa60 net/bluetooth/l2cap_core.c:6870
 l2cap_conn_add include/net/bluetooth/hci_core.h:1638 [inline]
 l2cap_chan_connect+0x15e5/0x2020 net/bluetooth/l2cap_core.c:7061
 bt_6lowpan_connect net/bluetooth/6lowpan.c:900 [inline]
 lowpan_control_write+0x3c9/0x740 net/bluetooth/6lowpan.c:1135
 full_proxy_write+0x13c/0x200 fs/debugfs/file.c:398
 vfs_write+0x2a0/0x1150 fs/read_write.c:684
 ksys_write+0x12a/0x250 fs/read_write.c:738
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 26076:
 kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
 kasan_save_track+0x14/0x30 mm/kasan/common.c:68
 kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:576
 poison_slab_object mm/kasan/common.c:247 [inline]
 __kasan_slab_free+0x51/0x70 mm/kasan/common.c:264
 kasan_slab_free include/linux/kasan.h:233 [inline]
 slab_free_hook mm/slub.c:2381 [inline]
 slab_free mm/slub.c:4643 [inline]
 kfree+0x2b4/0x4d0 mm/slub.c:4842
 l2cap_conn_free net/bluetooth/l2cap_core.c:1811 [inline]
 kref_put include/linux/kref.h:65 [inline]
 l2cap_conn_put net/bluetooth/l2cap_core.c:1823 [inline]
 l2cap_conn_del+0x59c/0x730 net/bluetooth/l2cap_core.c:1803
 l2cap_connect_cfm+0x9e1/0xf80 net/bluetooth/l2cap_core.c:7243
 hci_connect_cfm include/net/bluetooth/hci_core.h:2056 [inline]
 hci_conn_failed+0x1ba/0x330 net/bluetooth/hci_conn.c:1275
 hci_abort_conn_sync+0x762/0xb10 net/bluetooth/hci_sync.c:5645
 hci_disconnect_all_sync.constprop.0+0x104/0x3c0 net/bluetooth/hci_sync.c:5668
 hci_suspend_sync+0x770/0xab0 net/bluetooth/hci_sync.c:6145
 hci_suspend_dev+0x308/0x500 net/bluetooth/hci_core.c:2851
 hci_suspend_notifier+0x28d/0x2f0 net/bluetooth/hci_core.c:2422
 notifier_call_chain+0xb9/0x410 kernel/notifier.c:85
 notifier_call_chain_robust kernel/notifier.c:120 [inline]
 blocking_notifier_call_chain_robust kernel/notifier.c:345 [inline]
 blocking_notifier_call_chain_robust+0xc8/0x160 kernel/notifier.c:333
 pm_notifier_call_chain_robust+0x27/0x60 kernel/power/main.c:102
 snapshot_open+0x189/0x2b0 kernel/power/user.c:77
 misc_open+0x35a/0x420 drivers/char/misc.c:161
 chrdev_open+0x234/0x6a0 fs/char_dev.c:414
 do_dentry_open+0x744/0x1c10 fs/open.c:964
 vfs_open+0x82/0x3f0 fs/open.c:1094
 do_open fs/namei.c:3896 [inline]
 path_openat+0x1de4/0x2cb0 fs/namei.c:4055
 do_filp_open+0x20b/0x470 fs/namei.c:4082
 do_sys_openat2+0x11b/0x1d0 fs/open.c:1437
 do_sys_open fs/open.c:1452 [inline]
 __do_sys_openat fs/open.c:1468 [inline]
 __se_sys_openat fs/open.c:1463 [inline]
 __x64_sys_openat+0x174/0x210 fs/open.c:1463
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88807807b800
 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 688 bytes inside of
 freed 1024-byte region [ffff88807807b800, ffff88807807bc00)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x78078
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
anon flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801b841dc0 0000000000000000 dead000000000001
raw: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801b841dc0 0000000000000000 dead000000000001
head: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
head: 00fff00000000003 ffffea0001e01e01 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5718, tgid 5718 (dhcpcd-run-hook), ts 50410375153, free_ts 50186621838
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1c0/0x230 mm/page_alloc.c:1704
 prep_new_page mm/page_alloc.c:1712 [inline]
 get_page_from_freelist+0x1321/0x3890 mm/page_alloc.c:3669
 __alloc_frozen_pages_noprof+0x261/0x23f0 mm/page_alloc.c:4959
 alloc_pages_mpol+0x1fb/0x550 mm/mempolicy.c:2419
 alloc_slab_page mm/slub.c:2451 [inline]
 allocate_slab mm/slub.c:2619 [inline]
 new_slab+0x23b/0x330 mm/slub.c:2673
 ___slab_alloc+0xd9c/0x1940 mm/slub.c:3859
 __slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3949
 __slab_alloc_node mm/slub.c:4024 [inline]
 slab_alloc_node mm/slub.c:4185 [inline]
 __do_kmalloc_node mm/slub.c:4327 [inline]
 __kmalloc_noprof+0x2f2/0x510 mm/slub.c:4340
 kmalloc_noprof include/linux/slab.h:909 [inline]
 load_elf_phdrs+0x102/0x210 fs/binfmt_elf.c:525
 load_elf_binary+0x1fa/0x4f00 fs/binfmt_elf.c:854
 search_binary_handler fs/exec.c:1665 [inline]
 exec_binprm fs/exec.c:1697 [inline]
 bprm_execve fs/exec.c:1749 [inline]
 bprm_execve+0x8c0/0x1650 fs/exec.c:1725
 do_execveat_common.isra.0+0x4a5/0x610 fs/exec.c:1855
 do_execve fs/exec.c:1929 [inline]
 __do_sys_execve fs/exec.c:2005 [inline]
 __se_sys_execve fs/exec.c:2000 [inline]
 __x64_sys_execve+0x8e/0xb0 fs/exec.c:2000
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 5704 tgid 5704 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1248 [inline]
 __free_frozen_pages+0x7fe/0x1180 mm/page_alloc.c:2706
 discard_slab mm/slub.c:2717 [inline]
 __put_partials+0x16d/0x1c0 mm/slub.c:3186
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x4d/0x120 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x195/0x1e0 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x69/0x90 mm/kasan/common.c:329
 kasan_slab_alloc include/linux/kasan.h:250 [inline]
 slab_post_alloc_hook mm/slub.c:4148 [inline]
 slab_alloc_node mm/slub.c:4197 [inline]
 kmem_cache_alloc_noprof+0x1cb/0x3b0 mm/slub.c:4204
 getname_flags.part.0+0x4c/0x550 fs/namei.c:146
 getname_flags+0x93/0xf0 include/linux/audit.h:322
 getname include/linux/fs.h:2907 [inline]
 do_sys_openat2+0xb8/0x1d0 fs/open.c:1431
 do_sys_open fs/open.c:1452 [inline]
 __do_sys_openat fs/open.c:1468 [inline]
 __se_sys_openat fs/open.c:1463 [inline]
 __x64_sys_openat+0x174/0x210 fs/open.c:1463
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff88807807b980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88807807ba00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88807807ba80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                     ^
 ffff88807807bb00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88807807bb80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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