[PATCH] Bluetooth: hci_ldisc: Clear and shrink the ready bit

[Lizhi Xu]

syzbot reported a null ptr deref in qca_close. [1]

When registering hci fails, clear the hci uart protocal ready bit.
And shrink the ready bit window.

[1]
KASAN: null-ptr-deref in range [0x0000000000000158-0x000000000000015f]
CPU: 1 UID: 0 PID: 5837 Comm: syz-executor233 Not tainted 6.14.0-rc1-next-20250204-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
RIP: 0010:serial_clock_vote drivers/bluetooth/hci_qca.c:301 [inline]
RIP: 0010:qca_close+0x72/0x2e0 drivers/bluetooth/hci_qca.c:723
Code: 64 af f6 f8 48 89 2c 24 42 80 7c 2d 00 00 74 08 4c 89 f7 e8 20 28 5d f9 4d 8b 26 49 8d bc 24 5a 01 00 00 48 89 f8 48 c1 e8 03 <42> 0f b6 04 28 84 c0 4c 89 eb 0f 85 de 01 00 00 45 0f b6 ac 24 5a
RSP: 0018:ffffc90003cb79f0 EFLAGS: 00010206
RAX: 000000000000002b RBX: ffff888012bb2400 RCX: ffff88802e269e00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000000000015a
RBP: 1ffff110025764b7 R08: ffffffff8187d8b3 R09: 1ffffffff2860723
R10: dffffc0000000000 R11: ffffffff88c8a130 R12: 0000000000000000
R13: dffffc0000000000 R14: ffff888012bb25b8 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fbb3e1c10d0 CR3: 000000000e738000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 hci_uart_tty_close+0x205/0x290 drivers/bluetooth/hci_ldisc.c:557
 tty_ldisc_kill+0xa3/0x1a0 drivers/tty/tty_ldisc.c:613
 tty_ldisc_release+0x1a1/0x200 drivers/tty/tty_ldisc.c:781
 tty_release_struct+0x2b/0xe0 drivers/tty/tty_io.c:1690
 tty_release+0xd06/0x12c0 drivers/tty/tty_io.c:1861
 __fput+0x3e9/0x9f0 fs/file_table.c:448
 task_work_run+0x24f/0x310 kernel/task_work.c:227
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0xa2a/0x28e0 kernel/exit.c:938
 do_group_exit+0x207/0x2c0 kernel/exit.c:1087
 __do_sys_exit_group kernel/exit.c:1098 [inline]
 __se_sys_exit_group kernel/exit.c:1096 [inline]
 __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1096
 x64_sys_call+0x26a8/0x26b0 arch/x86/include/generated/asm/syscalls_64.h:232
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Fixes: c411c62cc133 ("Bluetooth: hci_uart: fix race during initialization")
Reported-by: syzbot+b9cff96f1ca33356d180@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=b9cff96f1ca33356d180
Tested-by: syzbot+b9cff96f1ca33356d180@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Lizhi Xu <lizhi.xu@xxxxxxxxxxxxx>
---
 drivers/bluetooth/hci_ldisc.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
index b955dc96b483..d5b97ff59330 100644
--- a/drivers/bluetooth/hci_ldisc.c
+++ b/drivers/bluetooth/hci_ldisc.c
@@ -683,8 +683,10 @@ static int hci_uart_register_dev(struct hci_uart *hu)
 	if (test_bit(HCI_UART_INIT_PENDING, &hu->hdev_flags))
 		return 0;
 
+	set_bit(HCI_UART_PROTO_READY, &hu->flags);
 	if (hci_register_dev(hdev) < 0) {
 		BT_ERR("Can't register HCI device");
+		clear_bit(HCI_UART_PROTO_READY, &hu->flags);
 		hu->proto->close(hu);
 		hu->hdev = NULL;
 		hci_free_dev(hdev);
@@ -707,8 +709,6 @@ static int hci_uart_set_proto(struct hci_uart *hu, int id)
 
 	hu->proto = p;
 
-	set_bit(HCI_UART_PROTO_READY, &hu->flags);
-
 	err = hci_uart_register_dev(hu);
 	if (err) {
 		return err;
-- 
2.43.0