linux-kernel - [PATCH v3 2/2] dmaengine: ti: k3-udma: Set rchan/tchan to NULL if a channel request fail

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Date:   Fri, 29 Oct 2021 20:42:51 +0530
From:   Kishon Vijay Abraham I <kishon@...com>
To:     Peter Ujfalusi <peter.ujfalusi@...il.com>,
        Vinod Koul <vkoul@...nel.org>
CC:     <dmaengine@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Vignesh Raghavendra <vigneshr@...com>,
        Kishon Vijay Abraham I <kishon@...com>
Subject: [PATCH v3 2/2] dmaengine: ti: k3-udma: Set rchan/tchan to NULL if a channel request fail

udma_get_*() checks if rchan/tchan/rflow is already allocated by checking
if it has a NON NULL value. For the error cases, rchan/tchan/rflow will
have error value and udma_get_*() considers this as already allocated
(PASS) since the error values are NON NULL. This results in NULL pointer
dereference error while de-referencing rchan/tchan/rflow.

Reset the value of rchan/tchan/rflow to NULL if a channel request fails.

Signed-off-by: Kishon Vijay Abraham I <kishon@...com>
---
 drivers/dma/ti/k3-udma.c | 24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/drivers/dma/ti/k3-udma.c b/drivers/dma/ti/k3-udma.c
index 14ae28830871..041d8e32d630 100644
--- a/drivers/dma/ti/k3-udma.c
+++ b/drivers/dma/ti/k3-udma.c
@@ -1380,6 +1380,7 @@ static int bcdma_get_bchan(struct udma_chan *uc)
 static int udma_get_tchan(struct udma_chan *uc)
 {
 	struct udma_dev *ud = uc->ud;
+	int ret;
 
 	if (uc->tchan) {
 		dev_dbg(ud->dev, "chan%d: already have tchan%d allocated\n",
@@ -1394,8 +1395,11 @@ static int udma_get_tchan(struct udma_chan *uc)
 	 */
 	uc->tchan = __udma_reserve_tchan(ud, uc->config.channel_tpl,
 					 uc->config.mapped_channel_id);
-	if (IS_ERR(uc->tchan))
-		return PTR_ERR(uc->tchan);
+	if (IS_ERR(uc->tchan)) {
+		ret = PTR_ERR(uc->tchan);
+		uc->tchan = NULL;
+		return ret;
+	}
 
 	if (ud->tflow_cnt) {
 		int tflow_id;
@@ -1425,6 +1429,7 @@ static int udma_get_tchan(struct udma_chan *uc)
 static int udma_get_rchan(struct udma_chan *uc)
 {
 	struct udma_dev *ud = uc->ud;
+	int ret;
 
 	if (uc->rchan) {
 		dev_dbg(ud->dev, "chan%d: already have rchan%d allocated\n",
@@ -1439,8 +1444,13 @@ static int udma_get_rchan(struct udma_chan *uc)
 	 */
 	uc->rchan = __udma_reserve_rchan(ud, uc->config.channel_tpl,
 					 uc->config.mapped_channel_id);
+	if (IS_ERR(uc->rchan)) {
+		ret = PTR_ERR(uc->rchan);
+		uc->rchan = NULL;
+		return ret;
+	}
 
-	return PTR_ERR_OR_ZERO(uc->rchan);
+	return 0;
 }
 
 static int udma_get_chan_pair(struct udma_chan *uc)
@@ -1494,6 +1504,7 @@ static int udma_get_chan_pair(struct udma_chan *uc)
 static int udma_get_rflow(struct udma_chan *uc, int flow_id)
 {
 	struct udma_dev *ud = uc->ud;
+	int ret;
 
 	if (!uc->rchan) {
 		dev_err(ud->dev, "chan%d: does not have rchan??\n", uc->id);
@@ -1507,8 +1518,13 @@ static int udma_get_rflow(struct udma_chan *uc, int flow_id)
 	}
 
 	uc->rflow = __udma_get_rflow(ud, flow_id);
+	if (IS_ERR(uc->rflow)) {
+		ret = PTR_ERR(uc->rflow);
+		uc->rflow = NULL;
+		return ret;
+	}
 
-	return PTR_ERR_OR_ZERO(uc->rflow);
+	return 0;
 }
 
 static void bcdma_put_bchan(struct udma_chan *uc)
-- 
2.17.1