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From:   gregkh@linuxfoundation.org
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Chaotian Jing <chaotian.jing@mediatek.com>,
        Ulf Hansson <ulf.hansson@linaro.org>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.9 20/78] mmc: mediatek: fix race condition between msdc_request_timeout and irq
Date:   Mon, 15 Mar 2021 14:51:43 +0100
Message-Id: <20210315135212.725857085@linuxfoundation.org>
In-Reply-To: <20210315135212.060847074@linuxfoundation.org>
References: <20210315135212.060847074@linuxfoundation.org>
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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

From: Chaotian Jing <chaotian.jing@mediatek.com>

[ Upstream commit 0354ca6edd464a2cf332f390581977b8699ed081 ]

when get request SW timeout, if CMD/DAT xfer done irq coming right now,
then there is race between the msdc_request_timeout work and irq handler,
and the host->cmd and host->data may set to NULL in irq handler. also,
current flow ensure that only one path can go to msdc_request_done(), so
no need check the return value of cancel_delayed_work().

Signed-off-by: Chaotian Jing <chaotian.jing@mediatek.com>
Link: https://lore.kernel.org/r/20201218071611.12276-1-chaotian.jing@mediatek.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/mmc/host/mtk-sd.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/mmc/host/mtk-sd.c b/drivers/mmc/host/mtk-sd.c
index 7fc6ce381142..125c06a10455 100644
--- a/drivers/mmc/host/mtk-sd.c
+++ b/drivers/mmc/host/mtk-sd.c
@@ -741,13 +741,13 @@ static void msdc_track_cmd_data(struct msdc_host *host,
 static void msdc_request_done(struct msdc_host *host, struct mmc_request *mrq)
 {
 	unsigned long flags;
-	bool ret;
 
-	ret = cancel_delayed_work(&host->req_timeout);
-	if (!ret) {
-		/* delay work already running */
-		return;
-	}
+	/*
+	 * No need check the return value of cancel_delayed_work, as only ONE
+	 * path will go here!
+	 */
+	cancel_delayed_work(&host->req_timeout);
+
 	spin_lock_irqsave(&host->lock, flags);
 	host->mrq = NULL;
 	spin_unlock_irqrestore(&host->lock, flags);
@@ -765,7 +765,7 @@ static bool msdc_cmd_done(struct msdc_host *host, int events,
 	bool done = false;
 	bool sbc_error;
 	unsigned long flags;
-	u32 *rsp = cmd->resp;
+	u32 *rsp;
 
 	if (mrq->sbc && cmd == mrq->cmd &&
 	    (events & (MSDC_INT_ACMDRDY | MSDC_INT_ACMDCRCERR
@@ -786,6 +786,7 @@ static bool msdc_cmd_done(struct msdc_host *host, int events,
 
 	if (done)
 		return true;
+	rsp = cmd->resp;
 
 	sdr_clr_bits(host->base + MSDC_INTEN, cmd_ints_mask);
 
@@ -968,7 +969,7 @@ static void msdc_data_xfer_next(struct msdc_host *host,
 static bool msdc_data_xfer_done(struct msdc_host *host, u32 events,
 				struct mmc_request *mrq, struct mmc_data *data)
 {
-	struct mmc_command *stop = data->stop;
+	struct mmc_command *stop;
 	unsigned long flags;
 	bool done;
 	unsigned int check_data = events &
@@ -984,6 +985,7 @@ static bool msdc_data_xfer_done(struct msdc_host *host, u32 events,
 
 	if (done)
 		return true;
+	stop = data->stop;
 
 	if (check_data || (stop && stop->error)) {
 		dev_dbg(host->dev, "DMA status: 0x%8X\n",
-- 
2.30.1