From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CB64530C366; Fri, 4 Sep 2026 05:49:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788500993; cv=none; b=OUOqtWzYMoI2Vxb3AzfA4LcPecwORXZN3VUgFw06fqWntwKxY+8Vkaw1rTc3pfqoTov/nTr9xlBICEf+UaMJGyrAFH9rtKkVd/XqRh4OvDCXzcwyGkzVWYlXNLj+4sjPkFks9sUWWbdZdzmgIJDTsVgXDbPbMIccDPZCRCQ7P2o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788500993; c=relaxed/simple; bh=qgwsXKErMMRsC0lBYWjrVftL90GHGk6zdqXAKvKkZEQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=MCquPRK/OMftkZpY3f63DI3aa3CPtR9jqo5BuNVy75d+jYsmNNVkw84n/SkIBZDwrMqfNOnxtYRTEKtMneHvtlS+00b+01CWGeB2SbHm3zeZYrp0T5R3gJXN+3AWZZJgpNDJu13kE3+fUExEgzp8HL0wHTLMoJFaN2PqX2nkYNM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=eq6HeSmx; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="eq6HeSmx" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 292A51F00A3D; Fri, 4 Sep 2026 05:49:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788500991; bh=FroW1wlD3APaeZ564LEMMpSWVS11PXaHkEjIdytvDRY=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=eq6HeSmx4yvR3etio+mkguN/NWwOZ7IJXSciMsnIGcUR8s+YOY/jwyCKOQe4ahxSM d5fPrc0N6507TltSTym0MkeMx1oIj2k6IG/QJnh9CJmyHf7ZN5ePa/n8SjvDXOS16f eSOwndj8ZpSMRTT2BTe7JlR+3XEsg6SCVvachTIs= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Xin Chen , Luiz Augusto von Dentz Subject: [PATCH 6.18 250/552] Bluetooth: hci_core: use skb_get() instead of skb_clone() for req_skb Date: Fri, 4 Sep 2026 06:56:47 +0200 Message-ID: <20260904045755.286289737@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260904045747.813364717@linuxfoundation.org> References: <20260904045747.813364717@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Xin Chen commit f5afdff569a09d1cb8cf19826199d024725576cb upstream. BT enable fails intermittently with -ETIMEDOUT (-110). The kernel log shows the HCI Read Local Version command was sent and the firmware replied with status 0x00 (logged by hci_req_cmd_complete() BT_DBG), but the waiter in __hci_cmd_sync_sk() never woke up and timed out after 10 s: bluetooth hci0: Opcode 0xfc00 // __hci_cmd_sync_sk bluetooth hci0: opcode 0xfc00 plen 1 // hci_cmd_sync_add bluetooth hci0: skb len 4 // hci_cmd_sync_alloc bluetooth hci0: length 1 // hci_req_sync_run Bluetooth: hci0 cmd_cnt 1 cmd queued 1 // hci_cmd_work Bluetooth: hci0 type 1 len 4 // hci_send_frame Bluetooth: opcode 0xfc00 status 0x00 // hci_req_cmd_complete <-- req_skb NULL: req_complete_skb not set, hci_cmd_sync_complete() never called, req_status stays HCI_REQ_PEND --> <-- 10 s later: wait_event_interruptible_timeout expires --> bluetooth hci0: end: err -110 // __hci_cmd_sync_sk The root cause is that hci_send_cmd_sync() clones the sent command into hdev->req_skb so that hci_req_cmd_complete() can locate the registered completion callback. Under memory pressure this skb_clone() fails, leaving hdev->req_skb NULL. The firmware reply is received and processed, but hci_req_cmd_complete() finds NULL req_skb, so hci_cmd_sync_complete() is never called, req_status stays HCI_REQ_PEND, and the waiter times out with -ETIMEDOUT. req_skb is only used to read bt_cb(skb)->hci callbacks and opcode -- it is never modified. Replace skb_clone() with skb_get(), which simply increments the reference count of hdev->sent_cmd without allocating new memory and therefore cannot fail. This issue was first observed as a use-after-free in ttyport_close() when ttyport_open() failed, which was investigated in an earlier patch series [1]. That investigation led to the discovery of the true root cause described above. [1] https://lore.kernel.org/all/20250430111617.1151390-1-quic_cxin@quicinc.com/ Fixes: 2615fd9a7c25 ("Bluetooth: hci_sync: Fix overwriting request callback") Cc: stable@vger.kernel.org Signed-off-by: Xin Chen Signed-off-by: Luiz Augusto von Dentz Signed-off-by: Greg Kroah-Hartman --- net/bluetooth/hci_core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/net/bluetooth/hci_core.c +++ b/net/bluetooth/hci_core.c @@ -4130,7 +4130,7 @@ static int hci_send_cmd_sync(struct hci_ if (READ_ONCE(hdev->req_status) == HCI_REQ_PEND && !hci_dev_test_and_set_flag(hdev, HCI_CMD_PENDING)) { kfree_skb(hdev->req_skb); - hdev->req_skb = skb_clone(hdev->sent_cmd, GFP_KERNEL); + hdev->req_skb = skb_get(hdev->sent_cmd); } return err;