From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793213498; b=H3o0oHDkaFJAr0zHlerLzWOj68zFYVNFD0+MIzNXO+UEbIxb1hDPluzWfvvDmsSvP86r HJTJNiTauxPXX7BUiWZ3OKnAaUee7Ta228NNBC+KK+vJowV4iCs2A/qEM7+2qSSyqOpOt V25Oj+rFjgyBrcTkE4wGgU4EBN1czyDQYW2Zs/GACTE3x33efvHbpAAfLyRIGc6GIVElW Fa1ZQayoldI+GEGhLqnkgcAU48Cef6NEG/83cnP4dezsxCwc/UgZ/fGQFNyawMxufSDi+ WzvYWSOiNTIfEGVdlw9y0QknI9XjuvjGyyL7sCu/n2C9VVfG/QxiGc9VuRE/taaJVkw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793213498; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=KpYsDT3f0o//sJv0f7+Bu9WskgzvbY9sCv9N+ajOyG8=; b=Cgn9ZmFSWqb9eCRx/T8Zy+sDpLjRF3YfX/w0aUhsnW451zexcAHnO05Nqg6mSy3DGT6L f17SjOwQfKKJV4DIFbppCPtUgLPxXLhThl1+5u+jtBQrNjmC7NR3eiw1tms/dQ/Mj+6ch zD+DkFUaWSOOF/GuEblQzM0vqjPVqukXs/DO9QjX1VgUL0ix/Byj0mqLk69C1Mf7RkGJd pLrZ3OOKG/Qng9sXl8SJqZfbMPN1hUjmbtbdkqF5THnMqdDrQYrL1+uwmpwfhZZemnsfv E5x+4sSm8mmL+pZa69iyfUm56oPXO9MNITe48oX/MkW/fOp2cMtgWZEJTANiHQ5AY3w== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=fSz2S3uY; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6D487606A31A; Wed, 28 Oct 2026 18:51:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=fSz2S3uY Received: by smtp.kernel.org (Postfix) with ESMTPSA id BCE601F01825; Wed, 28 Oct 2026 18:51:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793213498; bh=KpYsDT3f0o//sJv0f7+Bu9WskgzvbY9sCv9N+ajOyG8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=fSz2S3uYbrdQrwU0l07pfSFdpF7qg8De9co3n0tL6xTfS3tXkyigYK1eMC/VxbuSt DtwGHa8fOR4k//JWIZVSJT7wVS4iotnwA5xdWcoQH2yJ4wVZqX6xOla3/LVj7irtB+ 8dqiq7yWpKne+EMq2NuXoXxMDXu4rNadO0w1o/Sc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Pauli Virtanen , syzbot+74071deb72339c215b2e@syzkaller.appspotmail.com, Jiaming Zhang , Mikhail Gavrilov , Luiz Augusto von Dentz , Sasha Levin Subject: [PATCH 6.1 0525/1887] Bluetooth: RFCOMM: connect the session socket without rfcomm_mutex Date: Wed, 28 Oct 2026 17:43:41 +0100 Message-ID: <20261028170511.281944692@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261028170459.200466217@linuxfoundation.org> References: <20261028170459.200466217@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Mikhail Gavrilov [ Upstream commit ac022970e9fb0a5f7e7d1f6c8e104c1ed924dd1c ] An RFCOMM connect() issued while a BR/EDR link is being authenticated makes lockdep report a circular dependency, and the reported cycle is a real AB/BA between rfcomm_mutex and hdev->lock. rfcomm_security_cfm() is called from the HCI event path, which already holds hdev->lock: hci_rx_work() hci_event_packet() hci_cc_read_enc_key_size() [hdev->lock] hci_encrypt_cfm() [hci_cb_list_lock] rfcomm_security_cfm() [rfcomm_mutex] while an RFCOMM connect() from userspace takes the same two locks the other way round: rfcomm_sock_connect() rfcomm_dlc_open() [rfcomm_mutex] __rfcomm_dlc_open() rfcomm_session_create() kernel_connect() l2cap_sock_connect() l2cap_chan_connect() [hdev->lock] WARNING: possible circular locking dependency detected kworker/u131:1/1128 is trying to acquire lock: rfcomm_mutex, at: rfcomm_security_cfm+0x31/0x3e0 [rfcomm] but task is already holding lock: hci_cb_list_lock, at: hci_cc_read_enc_key_size+0x1d2/0xcc0 Chain exists of: rfcomm_mutex --> &hdev->lock --> hci_cb_list_lock hci_auth_complete_evt() and hci_encrypt_change_evt() reach the callback the same way. Both orders have to be seen in the same boot, which is why a BR/EDR connection alone is not enough to show it: a session set up by the remote side is created by rfcomm_accept_connection() in krfcommd, which calls kernel_accept() and never takes hdev->lock under rfcomm_mutex. Connecting a device that authenticates and encrypts the link and then calling connect() on an RFCOMM socket towards any address - the connect does not have to succeed, the order is recorded before the page timeout - reports it every time. Only the session socket has to be connected with the lock held, and it does not: nothing else can see the socket before it is put on the session list. So connect it first and take rfcomm_mutex afterwards, which removes the rfcomm_mutex -> hdev->lock order for good, rather than keeping the HCI event path out of rfcomm_mutex. rfcomm_session_create() becomes rfcomm_session_connect(), which returns the connected socket without touching the session list, and rfcomm_dlc_open() adds the session once it holds the lock again. If another opener added a session for the same pair while this socket was connecting, that session is used and this socket is dropped. __rfcomm_dlc_open() now takes the session it should use, and its state check runs after the lock is re-acquired, so a DLC that was opened or closed in the meantime is still handled. Over an existing ACL link the connection can complete before the session reaches the list, and the wakeup from the socket callback is then lost, so krfcommd is woken once the session is visible. Connecting without the lock opens a window in which the socket can be closed. The DLC is not on a session yet, so rfcomm_dlc_close() finds nothing to do and returns without touching it, and rfcomm_dlc_open() would then attach a DLC whose owner is gone. rfcomm_dlc_close() now marks such a DLC with RFCOMM_CLOSED, and rfcomm_dlc_open() checks the mark once it holds rfcomm_mutex again and drops the socket instead of attaching the DLC. The mark is cleared when an open starts, so a DLC that is reused is not affected. This covers both callers of rfcomm_dlc_open(), the socket and the tty layer. Fixes: 759c185d0bbd ("Bluetooth: RFCOMM: serialize security confirmation handling") Suggested-by: Pauli Virtanen Reported-by: Pauli Virtanen Closes: https://lore.kernel.org/linux-bluetooth/5e76a95e934e451e7006db28827c2d64af5a88be.camel@iki.fi/ Reported-by: syzbot+74071deb72339c215b2e@syzkaller.appspotmail.com Closes: https://lore.kernel.org/linux-bluetooth/6a92fadc.08e933ee.dbf97.008f.GAE@google.com/ Reported-by: Jiaming Zhang Closes: https://lore.kernel.org/all/CANypQFabseTuRiyz2pGkc_Qj0moGDnY7KEp1qdTOqkw6gAL3hw@mail.gmail.com/ Cc: stable@vger.kernel.org Signed-off-by: Mikhail Gavrilov Tested-by: syzbot+74071deb72339c215b2e@syzkaller.appspotmail.com Signed-off-by: Luiz Augusto von Dentz [ sashal: Changed the kernel_connect() address cast from struct sockaddr_unsized to struct sockaddr. ] Signed-off-by: Sasha Levin --- include/net/bluetooth/rfcomm.h | 1 + net/bluetooth/rfcomm/core.c | 134 +++++++++++++++++++++++---------- 2 files changed, 96 insertions(+), 39 deletions(-) diff --git a/include/net/bluetooth/rfcomm.h b/include/net/bluetooth/rfcomm.h index ba8d3702853d2..d483830188f38 100644 --- a/include/net/bluetooth/rfcomm.h +++ b/include/net/bluetooth/rfcomm.h @@ -210,6 +210,7 @@ struct rfcomm_dlc { #define RFCOMM_AUTH_REJECT 7 #define RFCOMM_DEFER_SETUP 8 #define RFCOMM_ENC_DROP 9 +#define RFCOMM_CLOSED 10 /* Scheduling flags and events */ #define RFCOMM_SCHED_WAKEUP 31 diff --git a/net/bluetooth/rfcomm/core.c b/net/bluetooth/rfcomm/core.c index 6324e03ff0d07..1e21e1e38543f 100644 --- a/net/bluetooth/rfcomm/core.c +++ b/net/bluetooth/rfcomm/core.c @@ -63,10 +63,9 @@ static void rfcomm_make_uih(struct sk_buff *skb, u8 addr); static void rfcomm_process_connect(struct rfcomm_session *s); -static struct rfcomm_session *rfcomm_session_create(bdaddr_t *src, - bdaddr_t *dst, - u8 sec_level, - int *err); +static struct socket *rfcomm_session_connect(bdaddr_t *src, bdaddr_t *dst, + u8 sec_level, int *err); +static struct rfcomm_session *rfcomm_session_add(struct socket *sock, int state); static struct rfcomm_session *rfcomm_session_get(bdaddr_t *src, bdaddr_t *dst); static struct rfcomm_session *rfcomm_session_del(struct rfcomm_session *s); @@ -364,28 +363,17 @@ static int rfcomm_check_channel(u8 channel) return channel < 1 || channel > 30; } -static int __rfcomm_dlc_open(struct rfcomm_dlc *d, bdaddr_t *src, bdaddr_t *dst, u8 channel) +static int __rfcomm_dlc_open(struct rfcomm_dlc *d, struct rfcomm_session *s, + u8 channel) { - struct rfcomm_session *s; - int err = 0; u8 dlci; - BT_DBG("dlc %p state %ld %pMR -> %pMR channel %d", - d, d->state, src, dst, channel); - - if (rfcomm_check_channel(channel)) - return -EINVAL; + BT_DBG("dlc %p state %ld session %p channel %d", + d, d->state, s, channel); if (d->state != BT_OPEN && d->state != BT_CLOSED) return 0; - s = rfcomm_session_get(src, dst); - if (!s) { - s = rfcomm_session_create(src, dst, d->sec_level, &err); - if (!s) - return err; - } - dlci = __dlci(__session_dir(s), channel); /* Check if DLCI already exists */ @@ -420,14 +408,84 @@ static int __rfcomm_dlc_open(struct rfcomm_dlc *d, bdaddr_t *src, bdaddr_t *dst, int rfcomm_dlc_open(struct rfcomm_dlc *d, bdaddr_t *src, bdaddr_t *dst, u8 channel) { - int r; + struct rfcomm_session *s; + struct socket *sock; + int err; + + BT_DBG("dlc %p state %ld %pMR -> %pMR channel %d", + d, d->state, src, dst, channel); + + if (rfcomm_check_channel(channel)) + return -EINVAL; rfcomm_lock(); - r = __rfcomm_dlc_open(d, src, dst, channel); + clear_bit(RFCOMM_CLOSED, &d->flags); + /* Do not page the remote device for a DLC that cannot be opened + * anyway. __rfcomm_dlc_open() looks at the state again once the + * lock has been re-acquired below. + */ + if (d->state != BT_OPEN && d->state != BT_CLOSED) { + rfcomm_unlock(); + return 0; + } + + s = rfcomm_session_get(src, dst); + if (s) { + err = __rfcomm_dlc_open(d, s, channel); + rfcomm_unlock(); + return err; + } rfcomm_unlock(); - return r; + + /* There is no session for this pair yet. kernel_connect() ends up in + * l2cap_chan_connect(), which takes hdev->lock, and the HCI event + * path takes rfcomm_mutex while holding hdev->lock, so the socket has + * to be connected with rfcomm_mutex released. + */ + sock = rfcomm_session_connect(src, dst, d->sec_level, &err); + if (!sock) + return err; + + rfcomm_lock(); + + /* The DLC may have been closed while the socket was connecting. It + * was not on a session, so rfcomm_dlc_close() could only mark it; + * attaching it now would leave it with no owner. + */ + if (test_bit(RFCOMM_CLOSED, &d->flags)) { + rfcomm_unlock(); + sock_release(sock); + return -ECONNRESET; + } + + /* Another opener may have added a session for the same pair in the + * meantime; that one is used and this socket is dropped. + */ + s = rfcomm_session_get(src, dst); + if (!s) { + s = rfcomm_session_add(sock, BT_BOUND); + if (s) { + s->initiator = 1; + sock = NULL; + } + } + + err = s ? __rfcomm_dlc_open(d, s, channel) : -ENOMEM; + + rfcomm_unlock(); + + if (sock) + sock_release(sock); + + /* Over an existing ACL link the connection can complete before the + * session reaches the list, and that wakeup is then lost, so let + * krfcommd look at the socket state now. + */ + rfcomm_schedule(); + + return err; } static void __rfcomm_dlc_disconn(struct rfcomm_dlc *d) @@ -507,8 +565,14 @@ int rfcomm_dlc_close(struct rfcomm_dlc *d, int err) rfcomm_lock(); s = d->session; - if (!s) + if (!s) { + /* Not on a session yet: rfcomm_dlc_open() may be connecting a + * socket for it with rfcomm_mutex released. Leave a mark so + * that it does not attach the DLC once it holds the lock again. + */ + set_bit(RFCOMM_CLOSED, &d->flags); goto no_session; + } /* after waiting on the mutex check the session still exists * then check the dlc still exists @@ -756,12 +820,12 @@ static struct rfcomm_session *rfcomm_session_close(struct rfcomm_session *s, return rfcomm_session_del(s); } -static struct rfcomm_session *rfcomm_session_create(bdaddr_t *src, - bdaddr_t *dst, - u8 sec_level, - int *err) +/* Creates the L2CAP socket a new session will run on and starts connecting + * it. Must be called with rfcomm_mutex released. + */ +static struct socket *rfcomm_session_connect(bdaddr_t *src, bdaddr_t *dst, + u8 sec_level, int *err) { - struct rfcomm_session *s = NULL; struct sockaddr_l2 addr; struct socket *sock; struct sock *sk; @@ -791,24 +855,16 @@ static struct rfcomm_session *rfcomm_session_create(bdaddr_t *src, l2cap_pi(sk)->chan->mode = L2CAP_MODE_ERTM; release_sock(sk); - s = rfcomm_session_add(sock, BT_BOUND); - if (!s) { - *err = -ENOMEM; - goto failed; - } - - s->initiator = 1; - bacpy(&addr.l2_bdaddr, dst); addr.l2_family = AF_BLUETOOTH; addr.l2_psm = cpu_to_le16(L2CAP_PSM_RFCOMM); addr.l2_cid = 0; addr.l2_bdaddr_type = BDADDR_BREDR; *err = kernel_connect(sock, (struct sockaddr *) &addr, sizeof(addr), O_NONBLOCK); - if (*err == 0 || *err == -EINPROGRESS) - return s; + if (*err && *err != -EINPROGRESS) + goto failed; - return rfcomm_session_del(s); + return sock; failed: sock_release(sock); -- 2.53.0