Bluetooth: iso: Fix circular lock in iso_conn_big_sync

This fixes the circular locking dependency warning below, by reworking
iso_sock_recvmsg, to ensure that the socket lock is always released
before calling a function that locks hdev.

[  561.670344] ======================================================
[  561.670346] WARNING: possible circular locking dependency detected
[  561.670349] 6.12.0-rc6+ torvalds#26 Not tainted
[  561.670351] ------------------------------------------------------
[  561.670353] iso-tester/3289 is trying to acquire lock:
[  561.670355] ffff88811f600078 (&hdev->lock){+.+.}-{3:3},
               at: iso_conn_big_sync+0x73/0x260 [bluetooth]
[  561.670405]
               but task is already holding lock:
[  561.670407] ffff88815af58258 (sk_lock-AF_BLUETOOTH){+.+.}-{0:0},
               at: iso_sock_recvmsg+0xbf/0x500 [bluetooth]
[  561.670450]
               which lock already depends on the new lock.

[  561.670452]
               the existing dependency chain (in reverse order) is:
[  561.670453]
               -> #2 (sk_lock-AF_BLUETOOTH){+.+.}-{0:0}:
[  561.670458]        lock_acquire+0x7c/0xc0
[  561.670463]        lock_sock_nested+0x3b/0xf0
[  561.670467]        bt_accept_dequeue+0x1a5/0x4d0 [bluetooth]
[  561.670510]        iso_sock_accept+0x271/0x830 [bluetooth]
[  561.670547]        do_accept+0x3dd/0x610
[  561.670550]        __sys_accept4+0xd8/0x170
[  561.670553]        __x64_sys_accept+0x74/0xc0
[  561.670556]        x64_sys_call+0x17d6/0x25f0
[  561.670559]        do_syscall_64+0x87/0x150
[  561.670563]        entry_SYSCALL_64_after_hwframe+0x76/0x7e
[  561.670567]
               -> #1 (sk_lock-AF_BLUETOOTH-BTPROTO_ISO){+.+.}-{0:0}:
[  561.670571]        lock_acquire+0x7c/0xc0
[  561.670574]        lock_sock_nested+0x3b/0xf0
[  561.670577]        iso_sock_listen+0x2de/0xf30 [bluetooth]
[  561.670617]        __sys_listen_socket+0xef/0x130
[  561.670620]        __x64_sys_listen+0xe1/0x190
[  561.670623]        x64_sys_call+0x2517/0x25f0
[  561.670626]        do_syscall_64+0x87/0x150
[  561.670629]        entry_SYSCALL_64_after_hwframe+0x76/0x7e
[  561.670632]
               -> #0 (&hdev->lock){+.+.}-{3:3}:
[  561.670636]        __lock_acquire+0x32ad/0x6ab0
[  561.670639]        lock_acquire.part.0+0x118/0x360
[  561.670642]        lock_acquire+0x7c/0xc0
[  561.670644]        __mutex_lock+0x18d/0x12f0
[  561.670647]        mutex_lock_nested+0x1b/0x30
[  561.670651]        iso_conn_big_sync+0x73/0x260 [bluetooth]
[  561.670687]        iso_sock_recvmsg+0x3e9/0x500 [bluetooth]
[  561.670722]        sock_recvmsg+0x1d5/0x240
[  561.670725]        sock_read_iter+0x27d/0x470
[  561.670727]        vfs_read+0x9a0/0xd30
[  561.670731]        ksys_read+0x1a8/0x250
[  561.670733]        __x64_sys_read+0x72/0xc0
[  561.670736]        x64_sys_call+0x1b12/0x25f0
[  561.670738]        do_syscall_64+0x87/0x150
[  561.670741]        entry_SYSCALL_64_after_hwframe+0x76/0x7e
[  561.670744]
               other info that might help us debug this:

[  561.670745] Chain exists of:
&hdev->lock --> sk_lock-AF_BLUETOOTH-BTPROTO_ISO --> sk_lock-AF_BLUETOOTH

[  561.670751]  Possible unsafe locking scenario:

[  561.670753]        CPU0                    CPU1
[  561.670754]        ----                    ----
[  561.670756]   lock(sk_lock-AF_BLUETOOTH);
[  561.670758]                                lock(sk_lock
                                              AF_BLUETOOTH-BTPROTO_ISO);
[  561.670761]                                lock(sk_lock-AF_BLUETOOTH);
[  561.670764]   lock(&hdev->lock);
[  561.670767]
                *** DEADLOCK ***

Fixes: 07a9342 ("Bluetooth: ISO: Send BIG Create Sync via hci_sync")
Signed-off-by: Iulia Tanasescu <[email protected]>
Signed-off-by: Luiz Augusto von Dentz <[email protected]>

net/bluetooth/iso.c

@@ -1411,6 +1411,7 @@ static void iso_conn_big_sync(struct sock *sk)
 	 * change.
 	 */
 	hci_dev_lock(hdev);
+	lock_sock(sk);
 
 	if (!test_and_set_bit(BT_SK_BIG_SYNC, &iso_pi(sk)->flags)) {
 		err = hci_le_big_create_sync(hdev, iso_pi(sk)->conn->hcon,
@@ -1423,6 +1424,7 @@ static void iso_conn_big_sync(struct sock *sk)
 				   err);
 	}
 
+	release_sock(sk);
 	hci_dev_unlock(hdev);
 }
 
@@ -1431,39 +1433,57 @@ static int iso_sock_recvmsg(struct socket *sock, struct msghdr *msg,
 {
 	struct sock *sk = sock->sk;
 	struct iso_pinfo *pi = iso_pi(sk);
+	bool early_ret = false;
+	int err = 0;
 
 	BT_DBG("sk %p", sk);
 
 	if (test_and_clear_bit(BT_SK_DEFER_SETUP, &bt_sk(sk)->flags)) {
+		sock_hold(sk);
 		lock_sock(sk);
+
 		switch (sk->sk_state) {
 		case BT_CONNECT2:
 			if (test_bit(BT_SK_PA_SYNC, &pi->flags)) {
+				release_sock(sk);
 				iso_conn_big_sync(sk);
+				lock_sock(sk);
+
 				sk->sk_state = BT_LISTEN;
 			} else {
 				iso_conn_defer_accept(pi->conn->hcon);
 				sk->sk_state = BT_CONFIG;
 			}
-			release_sock(sk);
-			return 0;
+
+			early_ret = true;
+			break;
 		case BT_CONNECTED:
 			if (test_bit(BT_SK_PA_SYNC, &iso_pi(sk)->flags)) {
+				release_sock(sk);
 				iso_conn_big_sync(sk);
+				lock_sock(sk);
+
 				sk->sk_state = BT_LISTEN;
-				release_sock(sk);
-				return 0;
+				early_ret = true;
 			}
 
-			release_sock(sk);
 			break;
 		case BT_CONNECT:
 			release_sock(sk);
-			return iso_connect_cis(sk);
+			err = iso_connect_cis(sk);
+			lock_sock(sk);
+
+			early_ret = true;
+			break;
 		default:
-			release_sock(sk);
 			break;
 		}
+
+		release_sock(sk);
+		sock_put(sk);
+
+		if (early_ret)
+			return err;
 	}
 
 	return bt_sock_recvmsg(sock, msg, len, flags);