========================= WARNING: held lock freed! syzkaller #0 Not tainted ------------------------- syz.0.55/6621 is freeing memory ffff0000ef218000-ffff0000ef2187ff, with a lock still held there! ffff0000ef218120 (sk_lock-AF_BLUETOOTH-BTPROTO_L2CAP){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1744 [inline] ffff0000ef218120 (sk_lock-AF_BLUETOOTH-BTPROTO_L2CAP){+.+.}-{0:0}, at: bt_accept_dequeue+0xe8/0x55c net/bluetooth/af_bluetooth.c:229 3 locks held by syz.0.55/6621: #0: ffff0000e1fd6810 (&sb->s_type->i_mutex_key#11){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:787 [inline] #0: ffff0000e1fd6810 (&sb->s_type->i_mutex_key#11){+.+.}-{3:3}, at: __sock_release net/socket.c:650 [inline] #0: ffff0000e1fd6810 (&sb->s_type->i_mutex_key#11){+.+.}-{3:3}, at: sock_close+0x7c/0x1f8 net/socket.c:1345 #1: ffff0000d8139120 (sk_lock-AF_BLUETOOTH-BTPROTO_L2CAP/2){+.+.}-{0:0}, at: l2cap_sock_release+0x60/0x1bc net/bluetooth/l2cap_sock.c:1419 #2: ffff0000ef218120 (sk_lock-AF_BLUETOOTH-BTPROTO_L2CAP){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1744 [inline] #2: ffff0000ef218120 (sk_lock-AF_BLUETOOTH-BTPROTO_L2CAP){+.+.}-{0:0}, at: bt_accept_dequeue+0xe8/0x55c net/bluetooth/af_bluetooth.c:229 stack backtrace: CPU: 1 PID: 6621 Comm: syz.0.55 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026 Call trace: dump_backtrace+0x0/0x458 arch/arm64/kernel/stacktrace.c:152 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:216 __dump_stack+0x30/0x40 lib/dump_stack.c:88 dump_stack_lvl+0xf4/0x15c lib/dump_stack.c:106 dump_stack+0x1c/0x5c lib/dump_stack.c:113 print_freed_lock_bug kernel/locking/lockdep.c:6401 [inline] debug_check_no_locks_freed+0x20c/0x29c kernel/locking/lockdep.c:6434 slab_free_hook mm/slub.c:1682 [inline] slab_free_freelist_hook+0x88/0x1e4 mm/slub.c:1736 slab_free mm/slub.c:3504 [inline] kfree+0x16c/0x400 mm/slub.c:4564 sk_prot_free net/core/sock.c:1905 [inline] __sk_destruct+0x43c/0x610 net/core/sock.c:1991 sk_destruct net/core/sock.c:2006 [inline] __sk_free+0x320/0x430 net/core/sock.c:2017 sk_free+0x68/0xd4 net/core/sock.c:2028 sock_put include/net/sock.h:1989 [inline] bt_accept_unlink+0x178/0x250 net/bluetooth/af_bluetooth.c:212 bt_accept_dequeue+0x3e8/0x55c net/bluetooth/af_bluetooth.c:258 l2cap_sock_cleanup_listen+0x44/0x284 net/bluetooth/l2cap_sock.c:1448 l2cap_sock_release+0x68/0x1bc net/bluetooth/l2cap_sock.c:1420 __sock_release net/socket.c:651 [inline] sock_close+0xb4/0x1f8 net/socket.c:1345 __fput+0x1c0/0x7e8 fs/file_table.c:311 ____fput+0x20/0x30 fs/file_table.c:339 task_work_run+0x12c/0x1d8 kernel/task_work.c:188 exit_task_work include/linux/task_work.h:33 [inline] do_exit+0x688/0x1f50 kernel/exit.c:884 do_group_exit+0x100/0x268 kernel/exit.c:998 get_signal+0x73c/0x1334 kernel/signal.c:2900 do_signal arch/arm64/kernel/signal.c:893 [inline] do_notify_resume+0x354/0x309c arch/arm64/kernel/signal.c:946 prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:133 [inline] exit_to_user_mode arch/arm64/kernel/entry-common.c:138 [inline] el0_svc+0xf0/0x1d0 arch/arm64/kernel/entry-common.c:609 el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584 ================================================================== BUG: KASAN: use-after-free in debug_spin_lock_before kernel/locking/spinlock_debug.c:85 [inline] BUG: KASAN: use-after-free in do_raw_spin_lock+0x244/0x2fc kernel/locking/spinlock_debug.c:114 Read of size 4 at addr ffff0000ef21808c by task syz.0.55/6621 CPU: 1 PID: 6621 Comm: syz.0.55 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026 Call trace: dump_backtrace+0x0/0x458 arch/arm64/kernel/stacktrace.c:152 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:216 __dump_stack+0x30/0x40 lib/dump_stack.c:88 dump_stack_lvl+0xf4/0x15c lib/dump_stack.c:106 print_address_description+0x78/0x30c mm/kasan/report.c:248 __kasan_report mm/kasan/report.c:434 [inline] kasan_report+0xec/0x158 mm/kasan/report.c:451 __asan_report_load4_noabort+0x44/0x50 mm/kasan/report_generic.c:308 debug_spin_lock_before kernel/locking/spinlock_debug.c:85 [inline] do_raw_spin_lock+0x244/0x2fc kernel/locking/spinlock_debug.c:114 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:136 [inline] _raw_spin_lock_bh+0x11c/0x1b4 kernel/locking/spinlock.c:178 spin_lock_bh include/linux/spinlock.h:369 [inline] release_sock+0x34/0x258 net/core/sock.c:3272 bt_accept_dequeue+0x4c8/0x55c net/bluetooth/af_bluetooth.c:262 l2cap_sock_cleanup_listen+0x44/0x284 net/bluetooth/l2cap_sock.c:1448 l2cap_sock_release+0x68/0x1bc net/bluetooth/l2cap_sock.c:1420 __sock_release net/socket.c:651 [inline] sock_close+0xb4/0x1f8 net/socket.c:1345 __fput+0x1c0/0x7e8 fs/file_table.c:311 ____fput+0x20/0x30 fs/file_table.c:339 task_work_run+0x12c/0x1d8 kernel/task_work.c:188 exit_task_work include/linux/task_work.h:33 [inline] do_exit+0x688/0x1f50 kernel/exit.c:884 do_group_exit+0x100/0x268 kernel/exit.c:998 get_signal+0x73c/0x1334 kernel/signal.c:2900 do_signal arch/arm64/kernel/signal.c:893 [inline] do_notify_resume+0x354/0x309c arch/arm64/kernel/signal.c:946 prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:133 [inline] exit_to_user_mode arch/arm64/kernel/entry-common.c:138 [inline] el0_svc+0xf0/0x1d0 arch/arm64/kernel/entry-common.c:609 el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584 Allocated by task 144: kasan_save_stack mm/kasan/common.c:38 [inline] kasan_set_track mm/kasan/common.c:46 [inline] set_alloc_info mm/kasan/common.c:434 [inline] ____kasan_kmalloc mm/kasan/common.c:513 [inline] __kasan_kmalloc+0xb0/0xf0 mm/kasan/common.c:522 kasan_kmalloc include/linux/kasan.h:264 [inline] __kmalloc+0x290/0x43c mm/slub.c:4412 kmalloc include/linux/slab.h:612 [inline] sk_prot_alloc+0xc4/0x1ec net/core/sock.c:1866 sk_alloc+0x40/0x384 net/core/sock.c:1922 l2cap_sock_alloc net/bluetooth/l2cap_sock.c:1879 [inline] l2cap_sock_new_connection_cb+0xdc/0x30c net/bluetooth/l2cap_sock.c:1482 l2cap_connect_cfm+0x2d4/0xd68 net/bluetooth/l2cap_core.c:8370 hci_connect_cfm include/net/bluetooth/hci_core.h:1507 [inline] hci_remote_features_evt+0x484/0x864 net/bluetooth/hci_event.c:3369 hci_event_packet+0x568/0x120c net/bluetooth/hci_event.c:6446 hci_rx_work+0x1cc/0x868 net/bluetooth/hci_core.c:5190 process_one_work+0x79c/0x1138 kernel/workqueue.c:2310 worker_thread+0x8f4/0x1034 kernel/workqueue.c:2457 kthread+0x374/0x454 kernel/kthread.c:334 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:856 Freed by task 6621: kasan_save_stack mm/kasan/common.c:38 [inline] kasan_set_track+0x4c/0x84 mm/kasan/common.c:46 kasan_set_free_info+0x28/0x4c mm/kasan/generic.c:360 ____kasan_slab_free+0x118/0x164 mm/kasan/common.c:366 __kasan_slab_free+0x18/0x28 mm/kasan/common.c:374 kasan_slab_free include/linux/kasan.h:230 [inline] slab_free_hook mm/slub.c:1710 [inline] slab_free_freelist_hook+0x128/0x1e4 mm/slub.c:1736 slab_free mm/slub.c:3504 [inline] kfree+0x16c/0x400 mm/slub.c:4564 sk_prot_free net/core/sock.c:1905 [inline] __sk_destruct+0x43c/0x610 net/core/sock.c:1991 sk_destruct net/core/sock.c:2006 [inline] __sk_free+0x320/0x430 net/core/sock.c:2017 sk_free+0x68/0xd4 net/core/sock.c:2028 sock_put include/net/sock.h:1989 [inline] bt_accept_unlink+0x178/0x250 net/bluetooth/af_bluetooth.c:212 bt_accept_dequeue+0x3e8/0x55c net/bluetooth/af_bluetooth.c:258 l2cap_sock_cleanup_listen+0x44/0x284 net/bluetooth/l2cap_sock.c:1448 l2cap_sock_release+0x68/0x1bc net/bluetooth/l2cap_sock.c:1420 __sock_release net/socket.c:651 [inline] sock_close+0xb4/0x1f8 net/socket.c:1345 __fput+0x1c0/0x7e8 fs/file_table.c:311 ____fput+0x20/0x30 fs/file_table.c:339 task_work_run+0x12c/0x1d8 kernel/task_work.c:188 exit_task_work include/linux/task_work.h:33 [inline] do_exit+0x688/0x1f50 kernel/exit.c:884 do_group_exit+0x100/0x268 kernel/exit.c:998 get_signal+0x73c/0x1334 kernel/signal.c:2900 do_signal arch/arm64/kernel/signal.c:893 [inline] do_notify_resume+0x354/0x309c arch/arm64/kernel/signal.c:946 prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:133 [inline] exit_to_user_mode arch/arm64/kernel/entry-common.c:138 [inline] el0_svc+0xf0/0x1d0 arch/arm64/kernel/entry-common.c:609 el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584 The buggy address belongs to the object at ffff0000ef218000 which belongs to the cache kmalloc-2k of size 2048 The buggy address is located 140 bytes inside of 2048-byte region [ffff0000ef218000, ffff0000ef218800) The buggy address belongs to the page: page:00000000d0986a2a refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x12f218 head:00000000d0986a2a order:3 compound_mapcount:0 compound_pincount:0 flags: 0x5ffc00000010200(slab|head|node=0|zone=2|lastcpupid=0x7ff) raw: 05ffc00000010200 dead000000000100 dead000000000122 ffff0000c0002900 raw: 0000000000000000 0000000000080008 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff0000ef217f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff0000ef218000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff0000ef218080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff0000ef218100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff0000ef218180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== ------------[ cut here ]------------ refcount_t: addition on 0; use-after-free. WARNING: CPU: 1 PID: 6621 at lib/refcount.c:25 refcount_warn_saturate+0x134/0x1f8 lib/refcount.c:25 Modules linked in: CPU: 1 PID: 6621 Comm: syz.0.55 Tainted: G B syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026 pstate: 62400005 (nZCv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--) pc : refcount_warn_saturate+0x134/0x1f8 lib/refcount.c:25 lr : refcount_warn_saturate+0x134/0x1f8 lib/refcount.c:25 sp : ffff8000201b7710 x29: ffff8000201b7710 x28: ffff0000ea2ca8d0 x27: ffff800012ece560 x26: ffff800012ecf000 x25: dfff800000000000 x24: dfff800000000000 x23: ffff0000dca9f000 x22: ffff0000ef218000 x21: ffff800012ece400 x20: ffff0000dca9f018 x19: ffff8000166f2000 x18: 0000000000000001 x17: 0000000000000000 x16: ffff800008304e30 x15: 00000000ffffffff x14: 0000000000000001 x13: 1ffff00004036e00 x12: 0000000000ff0100 x11: 0000000000000000 x10: 0000000000000000 x9 : fd714ad5f89c5100 x8 : fd714ad5f89c5100 x7 : 0000000000000001 x6 : 0000000000000001 x5 : ffff8000201b7018 x4 : ffff80001438f560 x3 : ffff800008304f40 x2 : 0000000000000001 x1 : 0000000100000000 x0 : 000000000000002a Call trace: refcount_warn_saturate+0x134/0x1f8 lib/refcount.c:25 __refcount_add include/linux/refcount.h:-1 [inline] __refcount_inc include/linux/refcount.h:250 [inline] refcount_inc include/linux/refcount.h:267 [inline] kref_get include/linux/kref.h:45 [inline] l2cap_chan_hold+0xa4/0x130 net/bluetooth/l2cap_core.c:519 l2cap_sock_cleanup_listen+0x98/0x284 net/bluetooth/l2cap_sock.c:1454 l2cap_sock_release+0x68/0x1bc net/bluetooth/l2cap_sock.c:1420 __sock_release net/socket.c:651 [inline] sock_close+0xb4/0x1f8 net/socket.c:1345 __fput+0x1c0/0x7e8 fs/file_table.c:311 ____fput+0x20/0x30 fs/file_table.c:339 task_work_run+0x12c/0x1d8 kernel/task_work.c:188 exit_task_work include/linux/task_work.h:33 [inline] do_exit+0x688/0x1f50 kernel/exit.c:884 do_group_exit+0x100/0x268 kernel/exit.c:998 get_signal+0x73c/0x1334 kernel/signal.c:2900 do_signal arch/arm64/kernel/signal.c:893 [inline] do_notify_resume+0x354/0x309c arch/arm64/kernel/signal.c:946 prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:133 [inline] exit_to_user_mode arch/arm64/kernel/entry-common.c:138 [inline] el0_svc+0xf0/0x1d0 arch/arm64/kernel/entry-common.c:609 el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584 irq event stamp: 2515 hardirqs last enabled at (2515): [] kasan_quarantine_put+0xc4/0x200 mm/kasan/quarantine.c:231 hardirqs last disabled at (2514): [] kasan_quarantine_put+0x108/0x200 mm/kasan/quarantine.c:204 softirqs last enabled at (2498): [] spin_unlock_bh include/linux/spinlock.h:409 [inline] softirqs last enabled at (2498): [] lock_sock_nested+0x14c/0x1d4 net/core/sock.c:3266 softirqs last disabled at (2496): [] spin_lock_bh include/linux/spinlock.h:369 [inline] softirqs last disabled at (2496): [] lock_sock_nested+0xf4/0x1d4 net/core/sock.c:3262 ---[ end trace 8fd51c9cae3ce031 ]--- ------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: CPU: 1 PID: 6621 at lib/refcount.c:28 refcount_warn_saturate+0x154/0x1f8 lib/refcount.c:28 Modules linked in: CPU: 1 PID: 6621 Comm: syz.0.55 Tainted: G B W syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026 pstate: 62400005 (nZCv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--) pc : refcount_warn_saturate+0x154/0x1f8 lib/refcount.c:28 lr : refcount_warn_saturate+0x154/0x1f8 lib/refcount.c:28 sp : ffff8000201b76b0 x29: ffff8000201b76b0 x28: ffff0000ea2ca8d0 x27: ffff800012ece560 x26: ffff800012ecf000 x25: dfff800000000000 x24: ffff0000dca9f01c x23: dfff800000000000 x22: dfff800000000000 x21: 00000000c0000000 x20: ffff0000dca9f018 x19: ffff8000166f2000 x18: 1fffe000341f2396 x17: 1fffe000341f2396 x16: ffff8000082d8c18 x15: ffff80001434eec0 x14: 0000000000000003 x13: 1ffff00004036dc4 x12: 0000000000ff0100 x11: 0000000000000000 x10: 0000000000000000 x9 : fd714ad5f89c5100 x8 : fd714ad5f89c5100 x7 : 0000000000000000 x6 : ffff800008248190 x5 : 0000000000000000 x4 : 0000000000000000 x3 : 0000000000000010 x2 : 0000000000000008 x1 : 0000000100000000 x0 : 0000000000000026 Call trace: refcount_warn_saturate+0x154/0x1f8 lib/refcount.c:28 __refcount_sub_and_test include/linux/refcount.h:283 [inline] __refcount_dec_and_test include/linux/refcount.h:315 [inline] refcount_dec_and_test include/linux/refcount.h:333 [inline] kref_put include/linux/kref.h:64 [inline] l2cap_chan_put+0x1a8/0x250 net/bluetooth/l2cap_core.c:537 l2cap_sock_kill+0xac/0x21c net/bluetooth/l2cap_sock.c:1256 l2cap_sock_cleanup_listen+0xf4/0x284 net/bluetooth/l2cap_sock.c:1459 l2cap_sock_release+0x68/0x1bc net/bluetooth/l2cap_sock.c:1420 __sock_release net/socket.c:651 [inline] sock_close+0xb4/0x1f8 net/socket.c:1345 __fput+0x1c0/0x7e8 fs/file_table.c:311 ____fput+0x20/0x30 fs/file_table.c:339 task_work_run+0x12c/0x1d8 kernel/task_work.c:188 exit_task_work include/linux/task_work.h:33 [inline] do_exit+0x688/0x1f50 kernel/exit.c:884 do_group_exit+0x100/0x268 kernel/exit.c:998 get_signal+0x73c/0x1334 kernel/signal.c:2900 do_signal arch/arm64/kernel/signal.c:893 [inline] do_notify_resume+0x354/0x309c arch/arm64/kernel/signal.c:946 prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:133 [inline] exit_to_user_mode arch/arm64/kernel/entry-common.c:138 [inline] el0_svc+0xf0/0x1d0 arch/arm64/kernel/entry-common.c:609 el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584 irq event stamp: 2515 hardirqs last enabled at (2515): [] kasan_quarantine_put+0xc4/0x200 mm/kasan/quarantine.c:231 hardirqs last disabled at (2514): [] kasan_quarantine_put+0x108/0x200 mm/kasan/quarantine.c:204 softirqs last enabled at (2498): [] spin_unlock_bh include/linux/spinlock.h:409 [inline] softirqs last enabled at (2498): [] lock_sock_nested+0x14c/0x1d4 net/core/sock.c:3266 softirqs last disabled at (2496): [] spin_lock_bh include/linux/spinlock.h:369 [inline] softirqs last disabled at (2496): [] lock_sock_nested+0xf4/0x1d4 net/core/sock.c:3262 ---[ end trace 8fd51c9cae3ce032 ]---