From patchwork Mon Jun 12 13:58:37 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hans Verkuil X-Patchwork-Id: 13276569 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 93F82C88CB4 for ; Mon, 12 Jun 2023 14:00:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233523AbjFLN7s (ORCPT ); Mon, 12 Jun 2023 09:59:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46174 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232421AbjFLN7r (ORCPT ); Mon, 12 Jun 2023 09:59:47 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0B443170B for ; Mon, 12 Jun 2023 06:59:18 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 9882F62987 for ; Mon, 12 Jun 2023 13:58:43 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 44A78C4339B; Mon, 12 Jun 2023 13:58:42 +0000 (UTC) From: Hans Verkuil To: linux-media@vger.kernel.org Cc: Zheng Zhang , Hans Verkuil Subject: [PATCH 1/3] media: cec: core: add adap_nb_transmit_canceled() callback Date: Mon, 12 Jun 2023 15:58:37 +0200 Message-Id: <20230612135839.254935-2-hverkuil-cisco@xs4all.nl> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230612135839.254935-1-hverkuil-cisco@xs4all.nl> References: <20230612135839.254935-1-hverkuil-cisco@xs4all.nl> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org A potential deadlock was found by Zheng Zhang with a local syzkaller instance. The problem is that when a non-blocking CEC transmit is canceled by calling cec_data_cancel, that in turn can call the high-level received() driver callback, which can call cec_transmit_msg() to transmit a new message. The cec_data_cancel() function is called with the adap->lock mutex held, and cec_transmit_msg() tries to take that same lock. The root cause is that the received() callback can either be used to pass on a received message (and then adap->lock is not held), or to report a canceled transmit (and then adap->lock is held). This is confusing, so create a new low-level adap_nb_transmit_canceled callback that reports back that a non-blocking transmit was canceled. And the received() callback is only called when a message is received, as was the case before commit f9d0ecbf56f4 ("media: cec: correctly pass on reply results") complicated matters. Reported-by: Zheng Zhang Signed-off-by: Hans Verkuil Fixes: f9d0ecbf56f4 ("media: cec: correctly pass on reply results") --- drivers/media/cec/core/cec-adap.c | 4 ++-- include/media/cec.h | 6 ++++-- 2 files changed, 6 insertions(+), 4 deletions(-) diff --git a/drivers/media/cec/core/cec-adap.c b/drivers/media/cec/core/cec-adap.c index 241b1621b197..f8cb8542e5e9 100644 --- a/drivers/media/cec/core/cec-adap.c +++ b/drivers/media/cec/core/cec-adap.c @@ -385,8 +385,8 @@ static void cec_data_cancel(struct cec_data *data, u8 tx_status, u8 rx_status) cec_queue_msg_monitor(adap, &data->msg, 1); if (!data->blocking && data->msg.sequence) - /* Allow drivers to process the message first */ - call_op(adap, received, &data->msg); + /* Allow drivers to react to a canceled transmit */ + call_op(adap, adap_nb_transmit_canceled, &data->msg); cec_data_completed(data); } diff --git a/include/media/cec.h b/include/media/cec.h index abee41ae02d0..6556cc161dc0 100644 --- a/include/media/cec.h +++ b/include/media/cec.h @@ -121,14 +121,16 @@ struct cec_adap_ops { void (*adap_configured)(struct cec_adapter *adap, bool configured); int (*adap_transmit)(struct cec_adapter *adap, u8 attempts, u32 signal_free_time, struct cec_msg *msg); + void (*adap_nb_transmit_canceled)(struct cec_adapter *adap, + const struct cec_msg *msg); void (*adap_status)(struct cec_adapter *adap, struct seq_file *file); void (*adap_free)(struct cec_adapter *adap); - /* Error injection callbacks */ + /* Error injection callbacks, called without adap->lock held */ int (*error_inj_show)(struct cec_adapter *adap, struct seq_file *sf); bool (*error_inj_parse_line)(struct cec_adapter *adap, char *line); - /* High-level CEC message callback */ + /* High-level CEC message callback, called without adap->lock held */ int (*received)(struct cec_adapter *adap, struct cec_msg *msg); };