linux-kernel - [PATCH 5/14 v3] PCI: pciehp: Check the return value of pcie_capability_read

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Message-Id: <20200710212026.27136-6-refactormyself@gmail.com>
Date:   Fri, 10 Jul 2020 23:20:17 +0200
From:   Saheed Olayemi Bolarinwa <refactormyself@...il.com>
To:     helgaas@...nel.org
Cc:     Bolarinwa Olayemi Saheed <refactormyself@...il.com>,
        bjorn@...gaas.com, Lukas Wunner <lukas@...ner.de>,
        skhan@...uxfoundation.org, linux-pci@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 5/14 v3] PCI: pciehp: Check the return value of pcie_capability_read_*()

From: Bolarinwa Olayemi Saheed <refactormyself@...il.com>

On any failure pcie_capability_read_word() sets it's last parameter,
*val to 0, this value may have be earlier set by pci_config_read_word()
to ~0. So, any function which check only for a frabricated ~0 will fail
in this case.

Checking for the return value of pcie_capability_read_dword() will help
assert failure or success of this function. But more checks may be needed
to assure the validity of the value.

Include a check on the return value of pcie_capability_read_word() to
confirm success or failure.

Suggested-by: Bjorn Helgaas <bjorn@...gaas.com>
Signed-off-by: Bolarinwa Olayemi Saheed <refactormyself@...il.com>

---
 drivers/pci/hotplug/pciehp_hpc.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
index 53433b37e181..5af281d97d4f 100644
--- a/drivers/pci/hotplug/pciehp_hpc.c
+++ b/drivers/pci/hotplug/pciehp_hpc.c
@@ -86,10 +86,11 @@ static int pcie_poll_cmd(struct controller *ctrl, int timeout)
 {
 	struct pci_dev *pdev = ctrl_dev(ctrl);
 	u16 slot_status;
+	int ret;
 
 	do {
-		pcie_capability_read_word(pdev, PCI_EXP_SLTSTA, &slot_status);
-		if (slot_status == (u16) ~0) {
+		ret = pcie_capability_read_word(pdev, PCI_EXP_SLTSTA, &slot_status);
+		if (ret || (slot_status == (u16) ~0)) {
 			ctrl_info(ctrl, "%s: no response from device\n",
 				  __func__);
 			return 0;
@@ -156,6 +157,7 @@ static void pcie_do_write_cmd(struct controller *ctrl, u16 cmd,
 {
 	struct pci_dev *pdev = ctrl_dev(ctrl);
 	u16 slot_ctrl_orig, slot_ctrl;
+	int ret;
 
 	mutex_lock(&ctrl->ctrl_lock);
 
@@ -164,8 +166,8 @@ static void pcie_do_write_cmd(struct controller *ctrl, u16 cmd,
 	 */
 	pcie_wait_cmd(ctrl);
 
-	pcie_capability_read_word(pdev, PCI_EXP_SLTCTL, &slot_ctrl);
-	if (slot_ctrl == (u16) ~0) {
+	ret = pcie_capability_read_word(pdev, PCI_EXP_SLTCTL, &slot_ctrl);
+	if (ret || (slot_ctrl == (u16) ~0)) {
 		ctrl_info(ctrl, "%s: no response from device\n", __func__);
 		goto out;
 	}
@@ -430,7 +432,7 @@ void pciehp_get_latch_status(struct controller *ctrl, u8 *status)
  * removed immediately after the check so the caller may need to take
  * this into account.
  *
- * It the hotplug controller itself is not available anymore returns
+ * If the hotplug controller itself is not available anymore returns
  * %-ENODEV.
  */
 int pciehp_card_present(struct controller *ctrl)
@@ -591,8 +593,8 @@ static irqreturn_t pciehp_isr(int irq, void *dev_id)
 	}
 
 read_status:
-	pcie_capability_read_word(pdev, PCI_EXP_SLTSTA, &status);
-	if (status == (u16) ~0) {
+	ret = pcie_capability_read_word(pdev, PCI_EXP_SLTSTA, &status);
+	if (ret || (status == (u16) ~0)) {
 		ctrl_info(ctrl, "%s: no response from device\n", __func__);
 		if (parent)
 			pm_runtime_put(parent);
-- 
2.18.2