From patchwork Fri Jun 23 17:18:38 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Pauli Virtanen X-Patchwork-Id: 695324 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2F7D0EB64DD for ; Fri, 23 Jun 2023 17:19:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232409AbjFWRTQ (ORCPT ); Fri, 23 Jun 2023 13:19:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47462 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232641AbjFWRS6 (ORCPT ); Fri, 23 Jun 2023 13:18:58 -0400 Received: from lahtoruutu.iki.fi (lahtoruutu.iki.fi [IPv6:2a0b:5c81:1c1::37]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0748D26BD for ; Fri, 23 Jun 2023 10:18:50 -0700 (PDT) Received: from monolith.lan (91-152-120-101.elisa-laajakaista.fi [91.152.120.101]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: pav) by lahtoruutu.iki.fi (Postfix) with ESMTPSA id 4QnkVJ0ZZMz49Q6x; Fri, 23 Jun 2023 20:18:48 +0300 (EEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=iki.fi; s=lahtoruutu; t=1687540728; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=83dDQcYbe5pUPhhpcZmbxd8AG+PU0UpwwamkIDyKTnc=; b=O1BRBGfQwA30r8jYsv/ICrk333+u0tmT5vJZUT90LXy9saBmNxa5PQi38n/x94ihgX4IEE 0L6fa/brW0rjIHm1AlikzezJ4OAQdqgZya9Hir8MJ3/PD0UeUF2NVsWLWlfUT3/ZUPs9SD A3YgDd3ZHKTITcUqEQgFGBk/2dTIaaD60iFmCvhzrsNU2JwK9+1hhwHcHuZ8Akn0JiDtap pmzVIlLc/ugIB+P5HsBm0UHE7A+L+az8XWRsdGoIPari5pqfgKm8dpYRT29x0PD9vmGcEv fqYSq0N5CtZtR7U8W0urUA9HMrzIZay5+w02mlFFJNM9idhi7hjbJXGa20ew2A== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=iki.fi; s=lahtoruutu; t=1687540728; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=83dDQcYbe5pUPhhpcZmbxd8AG+PU0UpwwamkIDyKTnc=; b=eA4220M6MRXLHtB3pGKTLnEnhjoTKdW4gf/SoR4s99ETkT3zfd4cN7eGnoJhpU3MbPqsyQ 8yUbGEqOJyTLSn1537jTDXcfx0Ro6zZdwWYh2b5TSL/1tYNPQJ7jVp4mmMR84PnlzOcfsL KWADrRC2UPT8mak+73wZvHcUtBCIdvSt9Aw1UY2TZv75qu4NkHHzZTZYnn297GCGD97ymb zph2nfALUJqbCtYX/mcyUzAzO+SH4igCsjSmWdwmc+uhV6usD5wQZBSU4OmNZNM1cdaGKT Ds6HmlDigoHXpsngZOGaMnGzHp+AAytcTyGDXFbgY7bdq17+bWMN3X4q5DQhYA== ARC-Authentication-Results: i=1; ORIGINATING; auth=pass smtp.auth=pav smtp.mailfrom=pav@iki.fi ARC-Seal: i=1; s=lahtoruutu; d=iki.fi; t=1687540728; a=rsa-sha256; cv=none; b=u6QMHw2+eNq9m5YagDl2g2hQC2dHpkujvJGcz/Oxd++LHOVoG3r1fApGJfBKrx8/fYcAPL fh1c5jmFDzeGbJ41+5IVR4Pn24qpWz/W7pa/KFOUhgOqvOLn3cj8TO6Wg3qDuBCSCDXKi4 eqwDy0mTQlQv940ibTCmzhOBhufyMD+xuFONl1B0wxRmGiJzKFNr6sC9a8LloSpOw+uLuJ fgPyfCUBb4liABKkKG1AUdMG+JR6FOQW2xwN9hBE4BPw/OJEa/Eo1xnFeghOlw/zb+WZRJ BW91KPEyvBYXJyARXGGeNeG4AwDhBR3vlKFIdB6UD6HOsJ38KvP4XWfxMgIBEQ== From: Pauli Virtanen To: linux-bluetooth@vger.kernel.org Cc: Pauli Virtanen Subject: [PATCH RFC 1/5] Bluetooth: hci_conn: add hci_conn_is_alive Date: Fri, 23 Jun 2023 20:18:38 +0300 Message-ID: <45455ee45ccb3313618a48c01be714e14d372257.1687525956.git.pav@iki.fi> X-Mailer: git-send-email 2.41.0 In-Reply-To: References: MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-bluetooth@vger.kernel.org A delayed operation such as hci_sync on a given hci_conn needs to take hci_conn_get, so that the hci_conn doesn't get freed in the meantime. This does not guarantee the conn is still alive in a valid state, as it may be cleaned up in the meantime, so one needs to check if it is still in conn_hash to know if it's still alive. Simplify this alive check, using HCI_CONN_DELETED flag. This is also meaningful with RCU lock only, but with slightly different semantics. If hci_conn_is_alive(conn) returns true inside rcu_read_lock, conn was in conn_hash from the point of view of the current task when the flag was read. Then its deletion cannot complete before rcu_read_unlock. Signed-off-by: Pauli Virtanen --- Notes: This probably can be done with RCU primitives setting list.prev, but that's maybe more magical... include/net/bluetooth/hci_core.h | 18 ++++++++++++++++++ net/bluetooth/hci_conn.c | 10 +--------- 2 files changed, 19 insertions(+), 9 deletions(-) diff --git a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/hci_core.h index 05a9b3ab3f56..cab39bdd0592 100644 --- a/include/net/bluetooth/hci_core.h +++ b/include/net/bluetooth/hci_core.h @@ -978,6 +978,7 @@ enum { HCI_CONN_PER_ADV, HCI_CONN_BIG_CREATED, HCI_CONN_CREATE_CIS, + HCI_CONN_DELETED, }; static inline bool hci_conn_ssp_enabled(struct hci_conn *conn) @@ -997,6 +998,7 @@ static inline bool hci_conn_sc_enabled(struct hci_conn *conn) static inline void hci_conn_hash_add(struct hci_dev *hdev, struct hci_conn *c) { struct hci_conn_hash *h = &hdev->conn_hash; + WARN_ON(test_bit(HCI_CONN_DELETED, &c->flags)); list_add_tail_rcu(&c->list, &h->list); switch (c->type) { case ACL_LINK: @@ -1023,6 +1025,10 @@ static inline void hci_conn_hash_add(struct hci_dev *hdev, struct hci_conn *c) static inline void hci_conn_hash_del(struct hci_dev *hdev, struct hci_conn *c) { struct hci_conn_hash *h = &hdev->conn_hash; + bool deleted; + + deleted = test_and_set_bit(HCI_CONN_DELETED, &c->flags); + WARN_ON(deleted); list_del_rcu(&c->list); synchronize_rcu(); @@ -1049,6 +1055,18 @@ static inline void hci_conn_hash_del(struct hci_dev *hdev, struct hci_conn *c) } } +/* With hdev->lock: whether hci_conn is in conn_hash. + * With RCU: if true, the hci_conn is valid conn_hash iteration cursor and + * hci_conn_hash_del has not completed. (Note that if hci_conn was obtained in + * this critical section it is always valid, but this may return false!) + */ +static inline bool hci_conn_is_alive(struct hci_dev *hdev, struct hci_conn *c) +{ + RCU_LOCKDEP_WARN(lockdep_is_held(&hdev->lock) || rcu_read_lock_held(), + "suspicious locking"); + return !test_bit(HCI_CONN_DELETED, &c->flags); +} + static inline unsigned int hci_conn_num(struct hci_dev *hdev, __u8 type) { struct hci_conn_hash *h = &hdev->conn_hash; diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c index 62a7ccfdfe63..d489a4829be7 100644 --- a/net/bluetooth/hci_conn.c +++ b/net/bluetooth/hci_conn.c @@ -183,21 +183,13 @@ static void le_scan_cleanup(struct work_struct *work) struct hci_conn *conn = container_of(work, struct hci_conn, le_scan_cleanup); struct hci_dev *hdev = conn->hdev; - struct hci_conn *c = NULL; BT_DBG("%s hcon %p", hdev->name, conn); hci_dev_lock(hdev); /* Check that the hci_conn is still around */ - rcu_read_lock(); - list_for_each_entry_rcu(c, &hdev->conn_hash.list, list) { - if (c == conn) - break; - } - rcu_read_unlock(); - - if (c == conn) { + if (hci_conn_is_alive(hdev, conn)) { hci_connect_le_scan_cleanup(conn, 0x00); hci_conn_cleanup(conn); }