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* [syzbot] [bluetooth?] KASAN: slab-use-after-free Write in bt_accept_dequeue
@ 2026-06-20  0:40 syzbot
  2026-06-20 11:20 ` Hillf Danton
  0 siblings, 1 reply; 2+ messages in thread
From: syzbot @ 2026-06-20  0:40 UTC (permalink / raw)
  To: linux-bluetooth, linux-kernel, luiz.dentz, marcel, syzkaller-bugs

Hello,

syzbot found the following issue on:

HEAD commit:    8c13415c8a43 Merge tag 'media/v7.2-1' of git://git.kernel...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12f94d56580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6a86d80fdec25236
dashboard link: https://syzkaller.appspot.com/bug?extid=674ff7e4d7fdfd572afc
compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/3ecc105c1b32/disk-8c13415c.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/cda6390db722/vmlinux-8c13415c.xz
kernel image: https://storage.googleapis.com/syzbot-assets/5f3d326d7d36/bzImage-8c13415c.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+674ff7e4d7fdfd572afc@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-use-after-free in instrument_atomic_read_write include/linux/instrumented.h:112 [inline]
BUG: KASAN: slab-use-after-free in atomic_fetch_add_relaxed include/linux/atomic/atomic-instrumented.h:252 [inline]
BUG: KASAN: slab-use-after-free in __refcount_add include/linux/refcount.h:283 [inline]
BUG: KASAN: slab-use-after-free in __refcount_inc include/linux/refcount.h:366 [inline]
BUG: KASAN: slab-use-after-free in refcount_inc include/linux/refcount.h:383 [inline]
BUG: KASAN: slab-use-after-free in sock_hold include/net/sock.h:839 [inline]
BUG: KASAN: slab-use-after-free in bt_accept_dequeue+0x6bd/0x920 net/bluetooth/af_bluetooth.c:348
Write of size 4 at addr ffff888036a17080 by task syz.2.3018/19569

CPU: 0 UID: 0 PID: 19569 Comm: syz.2.3018 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0x13d/0x4b0 mm/kasan/report.c:482
 kasan_report+0xdf/0x1c0 mm/kasan/report.c:595
 check_region_inline mm/kasan/generic.c:186 [inline]
 kasan_check_range+0x10f/0x1e0 mm/kasan/generic.c:200
 instrument_atomic_read_write include/linux/instrumented.h:112 [inline]
 atomic_fetch_add_relaxed include/linux/atomic/atomic-instrumented.h:252 [inline]
 __refcount_add include/linux/refcount.h:283 [inline]
 __refcount_inc include/linux/refcount.h:366 [inline]
 refcount_inc include/linux/refcount.h:383 [inline]
 sock_hold include/net/sock.h:839 [inline]
 bt_accept_dequeue+0x6bd/0x920 net/bluetooth/af_bluetooth.c:348
 l2cap_sock_cleanup_listen+0x47/0x4d0 net/bluetooth/l2cap_sock.c:1517
 l2cap_sock_release+0x69/0x280 net/bluetooth/l2cap_sock.c:1466
 __sock_release+0xb3/0x260 net/socket.c:710
 sock_close+0x1c/0x30 net/socket.c:1501
 __fput+0x3ff/0xb50 fs/file_table.c:512
 task_work_run+0x150/0x240 kernel/task_work.c:233
 get_signal+0x1bd/0x21e0 kernel/signal.c:2810
 arch_do_signal_or_restart+0x91/0x7e0 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:66 [inline]
 exit_to_user_mode_loop+0x139/0x6f0 kernel/entry/common.c:101
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline]
 do_syscall_64+0x666/0x870 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc6feb9ce59
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fc6ff9a4028 EFLAGS: 00000246 ORIG_RAX: 0000000000000120
RAX: fffffffffffffe00 RBX: 00007fc6fee15fa0 RCX: 00007fc6feb9ce59
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 00007fc6fec32e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000800 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc6fee16038 R14: 00007fc6fee15fa0 R15: 00007ffdf85f63a8
 </TASK>

Allocated by task 19587:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
 __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:415
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __do_kmalloc_node mm/slub.c:5334 [inline]
 __kmalloc_noprof+0x302/0x840 mm/slub.c:5347
 _kmalloc_noprof include/linux/slab.h:973 [inline]
 sk_prot_alloc+0x10b/0x2a0 net/core/sock.c:2252
 sk_alloc+0x36/0xe80 net/core/sock.c:2308
 bt_sock_alloc+0x3b/0x3c0 net/bluetooth/af_bluetooth.c:148
 l2cap_sock_alloc.constprop.0+0x33/0x1e0 net/bluetooth/l2cap_sock.c:1983
 l2cap_sock_new_connection_cb+0x10f/0x260 net/bluetooth/l2cap_sock.c:1562
 l2cap_connect_cfm+0x4e2/0xf80 net/bluetooth/l2cap_core.c:7481
 hci_connect_cfm include/net/bluetooth/hci_core.h:2136 [inline]
 hci_remote_features_evt+0x4f4/0x9b0 net/bluetooth/hci_event.c:3764
 hci_event_func net/bluetooth/hci_event.c:7800 [inline]
 hci_event_packet+0x8e9/0xcd0 net/bluetooth/hci_event.c:7851
 hci_rx_work+0x451/0xfc0 net/bluetooth/hci_core.c:4039
 process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
 process_scheduled_works kernel/workqueue.c:3405 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Freed by task 19569:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 kasan_save_free_info+0x3b/0x70 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5f/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2700 [inline]
 slab_free mm/slub.c:6310 [inline]
 kfree+0x22b/0x6c0 mm/slub.c:6625
 sk_prot_free net/core/sock.c:2291 [inline]
 __sk_destruct+0x88c/0xab0 net/core/sock.c:2391
 sk_destruct+0xc8/0xf0 net/core/sock.c:2419
 __sk_free+0xf4/0x3e0 net/core/sock.c:2430
 sk_free+0x61/0x90 net/core/sock.c:2441
 sock_put include/net/sock.h:2020 [inline]
 bt_accept_unlink+0x22a/0x370 net/bluetooth/af_bluetooth.c:267
 bt_accept_dequeue+0x791/0x920 net/bluetooth/af_bluetooth.c:336
 l2cap_sock_cleanup_listen+0x47/0x4d0 net/bluetooth/l2cap_sock.c:1517
 l2cap_sock_release+0x69/0x280 net/bluetooth/l2cap_sock.c:1466
 __sock_release+0xb3/0x260 net/socket.c:710
 sock_close+0x1c/0x30 net/socket.c:1501
 __fput+0x3ff/0xb50 fs/file_table.c:512
 task_work_run+0x150/0x240 kernel/task_work.c:233
 get_signal+0x1bd/0x21e0 kernel/signal.c:2810
 arch_do_signal_or_restart+0x91/0x7e0 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:66 [inline]
 exit_to_user_mode_loop+0x139/0x6f0 kernel/entry/common.c:101
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline]
 do_syscall_64+0x666/0x870 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888036a17000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 128 bytes inside of
 freed 2048-byte region [ffff888036a17000, ffff888036a17800)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff888036a16000 pfn:0x36a10
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000240(workingset|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000240 ffff88813fe3b000 ffffea000132c210 ffffea00009e2810
raw: ffff888036a16000 0000000800080005 00000000f5000000 0000000000000000
head: 00fff00000000240 ffff88813fe3b000 ffffea000132c210 ffffea00009e2810
head: ffff888036a16000 0000000800080005 00000000f5000000 0000000000000000
head: 00fff00000000003 fffffffffffffe01 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 10, tgid 10 (kworker/0:1), ts 48507424327, free_ts 27518573283
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0xfd/0x120 mm/page_alloc.c:1853
 prep_new_page mm/page_alloc.c:1861 [inline]
 get_page_from_freelist+0x812/0x3d20 mm/page_alloc.c:3941
 __alloc_frozen_pages_noprof+0x27c/0x2b60 mm/page_alloc.c:5221
 alloc_slab_page mm/slub.c:3289 [inline]
 allocate_slab mm/slub.c:3404 [inline]
 new_slab+0xa2/0x670 mm/slub.c:3447
 refill_objects+0xe3/0x430 mm/slub.c:7241
 refill_sheaf mm/slub.c:2827 [inline]
 __pcs_replace_empty_main+0x375/0x660 mm/slub.c:4692
 alloc_from_pcs mm/slub.c:4790 [inline]
 slab_alloc_node mm/slub.c:4924 [inline]
 __do_kmalloc_node mm/slub.c:5333 [inline]
 __kmalloc_node_track_caller_noprof+0x6b5/0x890 mm/slub.c:5438
 kmalloc_reserve+0xe8/0x350 net/core/skbuff.c:637
 __alloc_skb+0x185/0x710 net/core/skbuff.c:715
 alloc_skb include/linux/skbuff.h:1386 [inline]
 mld_newpack.isra.0+0x18e/0xa20 net/ipv6/mcast.c:1773
 add_grhead+0x299/0x340 net/ipv6/mcast.c:1884
 add_grec+0x1389/0x1930 net/ipv6/mcast.c:2023
 mld_send_cr net/ipv6/mcast.c:2148 [inline]
 mld_ifc_work+0x3c5/0xc10 net/ipv6/mcast.c:2694
 process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
 process_scheduled_works kernel/workqueue.c:3405 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
 kthread+0x370/0x450 kernel/kthread.c:436
page last free pid 5380 tgid 5380 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1397 [inline]
 __free_frozen_pages+0x794/0x10a0 mm/page_alloc.c:2938
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x47/0xf0 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x1a0/0x1f0 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:4610 [inline]
 slab_alloc_node mm/slub.c:4939 [inline]
 kmem_cache_alloc_noprof+0x241/0x6d0 mm/slub.c:4946
 vm_area_alloc+0x1f/0x160 mm/vma_init.c:32
 __mmap_new_vma mm/vma.c:2547 [inline]
 __mmap_region+0x104d/0x2dd0 mm/vma.c:2771
 mmap_region+0x35d/0x620 mm/vma.c:2857
 do_mmap+0xc63/0x12f0 mm/mmap.c:560
 vm_mmap_pgoff+0x29e/0x470 mm/util.c:581
 ksys_mmap_pgoff+0xe4/0x610 mm/mmap.c:606
 __do_sys_mmap arch/x86/kernel/sys_x86_64.c:89 [inline]
 __se_sys_mmap arch/x86/kernel/sys_x86_64.c:82 [inline]
 __x64_sys_mmap+0x125/0x190 arch/x86/kernel/sys_x86_64.c:82
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff888036a16f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888036a17000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888036a17080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff888036a17100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888036a17180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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^ permalink raw reply	[flat|nested] 2+ messages in thread
end of thread, other threads:[~2026-06-20 11:21 UTC | newest]

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2026-06-20  0:40 [syzbot] [bluetooth?] KASAN: slab-use-after-free Write in bt_accept_dequeue syzbot
2026-06-20 11:20 ` Hillf Danton

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