linux-kernel - [PATCH] slimbus: qcom: fix potential NULL dereference in qcom_slim_prg

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Date:   Tue, 8 Dec 2020 09:54:32 +0800
From:   Zhang Changzhong <zhangchangzhong@...wei.com>
To:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Sagar Dharia <sdharia@...eaurora.org>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>
CC:     Zhang Changzhong <zhangchangzhong@...wei.com>,
        <linux-arm-msm@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH] slimbus: qcom: fix potential NULL dereference in qcom_slim_prg_slew()

platform_get_resource_byname() may fail and in this case a NULL
dereference will occur.

Fix it to use devm_platform_ioremap_resource_byname() instead of calling
platform_get_resource_byname() and devm_ioremap().

This is detected by Coccinelle semantic patch.

@@
expression pdev, res, n, t, e, e1, e2;
@@

res = \(platform_get_resource\|platform_get_resource_byname\)(pdev, t,
n);
+ if (!res)
+   return -EINVAL;
... when != res == NULL
e = devm_ioremap(e1, res->start, e2);

Fixes: ad7fcbc308b0 ("slimbus: qcom: Add Qualcomm Slimbus controller driver")
Signed-off-by: Zhang Changzhong <zhangchangzhong@...wei.com>
---
 drivers/slimbus/qcom-ctrl.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/drivers/slimbus/qcom-ctrl.c b/drivers/slimbus/qcom-ctrl.c
index 4aad256..f04b961 100644
--- a/drivers/slimbus/qcom-ctrl.c
+++ b/drivers/slimbus/qcom-ctrl.c
@@ -472,15 +472,10 @@ static void qcom_slim_rxwq(struct work_struct *work)
 static void qcom_slim_prg_slew(struct platform_device *pdev,
 				struct qcom_slim_ctrl *ctrl)
 {
-	struct resource	*slew_mem;
-
 	if (!ctrl->slew_reg) {
 		/* SLEW RATE register for this SLIMbus */
-		slew_mem = platform_get_resource_byname(pdev, IORESOURCE_MEM,
-				"slew");
-		ctrl->slew_reg = devm_ioremap(&pdev->dev, slew_mem->start,
-				resource_size(slew_mem));
-		if (!ctrl->slew_reg)
+		ctrl->slew_reg = devm_platform_ioremap_resource_byname(pdev, "slew");
+		if (IS_ERR(ctrl->slew_reg))
 			return;
 	}
 
-- 
2.9.5