From: Luiz Augusto von Dentz luiz.von.dentz@intel.com
[ Upstream commit ecb9a843be4d6fd710d7026e359f21015a062572 ]
BUG: KASAN: slab-use-after-free in sco_conn_free net/bluetooth/sco.c:87 [inline] BUG: KASAN: slab-use-after-free in kref_put include/linux/kref.h:65 [inline] BUG: KASAN: slab-use-after-free in sco_conn_put+0xdd/0x410 net/bluetooth/sco.c:107 Write of size 8 at addr ffff88811cb96b50 by task kworker/u17:4/352
CPU: 1 UID: 0 PID: 352 Comm: kworker/u17:4 Not tainted 6.17.0-rc5-g717368f83676 #4 PREEMPT(voluntary) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 Workqueue: hci13 hci_cmd_sync_work Call Trace: <TASK> __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x10b/0x170 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [inline] print_report+0x191/0x550 mm/kasan/report.c:482 kasan_report+0xc4/0x100 mm/kasan/report.c:595 sco_conn_free net/bluetooth/sco.c:87 [inline] kref_put include/linux/kref.h:65 [inline] sco_conn_put+0xdd/0x410 net/bluetooth/sco.c:107 sco_connect_cfm+0xb4/0xae0 net/bluetooth/sco.c:1441 hci_connect_cfm include/net/bluetooth/hci_core.h:2082 [inline] hci_conn_failed+0x20a/0x2e0 net/bluetooth/hci_conn.c:1313 hci_conn_unlink+0x55f/0x810 net/bluetooth/hci_conn.c:1121 hci_conn_del+0xb6/0x1110 net/bluetooth/hci_conn.c:1147 hci_abort_conn_sync+0x8c5/0xbb0 net/bluetooth/hci_sync.c:5689 hci_cmd_sync_work+0x281/0x380 net/bluetooth/hci_sync.c:332 process_one_work kernel/workqueue.c:3236 [inline] process_scheduled_works+0x77e/0x1040 kernel/workqueue.c:3319 worker_thread+0xbee/0x1200 kernel/workqueue.c:3400 kthread+0x3c7/0x870 kernel/kthread.c:463 ret_from_fork+0x13a/0x1e0 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 </TASK>
Allocated by task 31370: kasan_save_stack mm/kasan/common.c:47 [inline] kasan_save_track+0x30/0x70 mm/kasan/common.c:68 poison_kmalloc_redzone mm/kasan/common.c:388 [inline] __kasan_kmalloc+0x82/0x90 mm/kasan/common.c:405 kasan_kmalloc include/linux/kasan.h:260 [inline] __do_kmalloc_node mm/slub.c:4382 [inline] __kmalloc_noprof+0x22f/0x390 mm/slub.c:4394 kmalloc_noprof include/linux/slab.h:909 [inline] sk_prot_alloc+0xae/0x220 net/core/sock.c:2239 sk_alloc+0x34/0x5a0 net/core/sock.c:2295 bt_sock_alloc+0x3c/0x330 net/bluetooth/af_bluetooth.c:151 sco_sock_alloc net/bluetooth/sco.c:562 [inline] sco_sock_create+0xc0/0x350 net/bluetooth/sco.c:593 bt_sock_create+0x161/0x3b0 net/bluetooth/af_bluetooth.c:135 __sock_create+0x3ad/0x780 net/socket.c:1589 sock_create net/socket.c:1647 [inline] __sys_socket_create net/socket.c:1684 [inline] __sys_socket+0xd5/0x330 net/socket.c:1731 __do_sys_socket net/socket.c:1745 [inline] __se_sys_socket net/socket.c:1743 [inline] __x64_sys_socket+0x7a/0x90 net/socket.c:1743 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xc7/0x240 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f
Freed by task 31374: kasan_save_stack mm/kasan/common.c:47 [inline] kasan_save_track+0x30/0x70 mm/kasan/common.c:68 kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:576 poison_slab_object mm/kasan/common.c:243 [inline] __kasan_slab_free+0x3d/0x50 mm/kasan/common.c:275 kasan_slab_free include/linux/kasan.h:233 [inline] slab_free_hook mm/slub.c:2428 [inline] slab_free mm/slub.c:4701 [inline] kfree+0x199/0x3b0 mm/slub.c:4900 sk_prot_free net/core/sock.c:2278 [inline] __sk_destruct+0x4aa/0x630 net/core/sock.c:2373 sco_sock_release+0x2ad/0x300 net/bluetooth/sco.c:1333 __sock_release net/socket.c:649 [inline] sock_close+0xb8/0x230 net/socket.c:1439 __fput+0x3d1/0x9e0 fs/file_table.c:468 task_work_run+0x206/0x2a0 kernel/task_work.c:227 get_signal+0x1201/0x1410 kernel/signal.c:2807 arch_do_signal_or_restart+0x34/0x740 arch/x86/kernel/signal.c:337 exit_to_user_mode_loop+0x68/0xc0 kernel/entry/common.c:40 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+0x1dd/0x240 arch/x86/entry/syscall_64.c:100 entry_SYSCALL_64_after_hwframe+0x77/0x7f
Reported-by: cen zhang zzzccc427@gmail.com Signed-off-by: Luiz Augusto von Dentz luiz.von.dentz@intel.com Signed-off-by: Sasha Levin sashal@kernel.org ---
LLM Generated explanations, may be completely bogus:
YES **Why It Matters** - The crash comes from `sco_conn_free` writing through `conn->sk` even after the socket is destroyed; that code (net/bluetooth/sco.c:80-93) assumes `conn->sk` still points to a live socket and dereferences it, matching the KASAN trace in the commit message. - In the orphan-socket path (`sco_sock_release` → `sco_sock_kill`, net/bluetooth/sco.c:1332-1344 and :494-506) the connection’s back pointer was never cleared, so the destructor path would free the socket while the connection still held a stale pointer, leading to the observed UAF.
**How The Fix Helps** - The new block in `sco_sock_kill` (net/bluetooth/sco.c:501-505) acquires the per-connection spinlock and sets `conn->sk = NULL` before the final `sock_put(sk)`. As a result, `sco_conn_free` now sees a NULL pointer and skips the dereference, eliminating the UAF. - This mirrors the already-safe release path in `sco_chan_del`, which has long cleared `conn->sk` under the same lock (net/bluetooth/sco.c:242-247), so the fix simply brings the orphan cleanup path in line with existing, proven logic.
**Risk Assessment** - Patch is self-contained and tiny: one guarded assignment under an existing spinlock in a single file, with no ABI or behavioral changes for healthy sockets. - It specifically targets a genuine crash seen on 6.17-rc5, affecting failing/aborted SCO connections; leaving it unfixed keeps a reproducible UAF around kernel worker threads. - The locking used is already standard for this structure, so the regression surface is negligible—other code that needs `conn->sk` already holds the same lock and tolerates NULL.
**Backport Notes** - No new helpers or dependencies are introduced, so the change applies cleanly to maintained stable branches that still share this SCO logic. - Given the real-world crash, low risk, and narrow scope, this is an excellent candidate for stable backporting.
net/bluetooth/sco.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/net/bluetooth/sco.c b/net/bluetooth/sco.c index d382d980fd9a7..ab0cf442d57b9 100644 --- a/net/bluetooth/sco.c +++ b/net/bluetooth/sco.c @@ -498,6 +498,13 @@ static void sco_sock_kill(struct sock *sk)
BT_DBG("sk %p state %d", sk, sk->sk_state);
+ /* Sock is dead, so set conn->sk to NULL to avoid possible UAF */ + if (sco_pi(sk)->conn) { + sco_conn_lock(sco_pi(sk)->conn); + sco_pi(sk)->conn->sk = NULL; + sco_conn_unlock(sco_pi(sk)->conn); + } + /* Kill poor orphan */ bt_sock_unlink(&sco_sk_list, sk); sock_set_flag(sk, SOCK_DEAD);