CVE-2025-39860: In the Linux kernel, the following vulnerability has been resolved:  Bluetooth: Fix use-after-free in l2cap_sock_cleanup_listen()  syzbot reported the splat below without a repro.  In the splat, a single thread calling bt_accept_dequeue() freed sk and touched it after that.  The root cause would be the racy l2cap_sock_cleanup_listen() call added by the cited commit.  bt_accept_dequeue() is called under lock_sock() except for l2cap_sock_release().  Two threads could see the same socket during the list iteration in bt_accept_dequeue():    CPU1                        CPU2 (close())   ----                        ----   sock_hold(sk)               sock_hold(sk);   lock_sock(sk)   <-- block close()   sock_put(sk)   bt_accept_unlink(sk)     sock_put(sk)  <-- refcnt by bt_accept_enqueue()   release_sock(sk)                               lock_sock(sk)                               sock_put(sk)                               bt_accept_unlink(sk)                                 sock_put(sk)        <-- last refcnt                               bt_accept_unlink(sk)  <-- UAF  Depending on the timing, the other thread could show up in the "Freed by task" part.  Let's call l2cap_sock_cleanup_listen() under lock_sock() in l2cap_sock_release().  [0]: BUG: KASAN: slab-use-after-free in debug_spin_lock_before kernel/locking/spinlock_debug.c:86 [inline] BUG: KASAN: slab-use-after-free in do_raw_spin_lock+0x26f/0x2b0 kernel/locking/spinlock_debug.c:115 Read of size 4 at addr ffff88803b7eb1c4 by task syz.5.3276/16995 CPU: 3 UID: 0 PID: 16995 Comm: syz.5.3276 Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 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  debug_spin_lock_before kernel/locking/spinlock_debug.c:86 [inline]  do_raw_spin_lock+0x26f/0x2b0 kernel/locking/spinlock_debug.c:115  spin_lock_bh include/linux/spinlock.h:356 [inline]  release_sock+0x21/0x220 net/core/sock.c:3746  bt_accept_dequeue+0x505/0x600 net/bluetooth/af_bluetooth.c:312  l2cap_sock_cleanup_listen+0x5c/0x2a0 net/bluetooth/l2cap_sock.c:1451  l2cap_sock_release+0x5c/0x210 net/bluetooth/l2cap_sock.c:1425  __sock_release+0xb3/0x270 net/socket.c:649  sock_close+0x1c/0x30 net/socket.c:1439  __fput+0x3ff/0xb70 fs/file_table.c:468  task_work_run+0x14d/0x240 kernel/task_work.c:227  resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]  exit_to_user_mode_loop+0xeb/0x110 kernel/entry/common.c:43  exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]  syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]  syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]  do_syscall_64+0x3f6/0x4c0 arch/x86/entry/syscall_64.c:100  entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f2accf8ebe9 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffdb6cb1378 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4 RAX: 0000000000000000 RBX: 00000000000426fb RCX: 00007f2accf8ebe9 RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003 RBP: 00007f2acd1b7da0 R08: 0000000000000001 R09: 00000012b6cb166f R10: 0000001b30e20000 R11: 0000000000000246 R12: 00007f2acd1b609c R13: 00007f2acd1b6090 R14: ffffffffffffffff R15: 00007ffdb6cb1490  </TASK>  Allocated by task 5326:  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:388 [inline]  __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:405  kasan_kmalloc include/linux/kasan.h:260 [inline]  __do_kmalloc_node mm/slub.c:4365 [inline]  __kmalloc_nopro ---truncated---