linux-kernel - [PATCH 10/11 RFC] PCI/ASPM: Use error return value from pcie_capability_read

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Message-Id: <20200706093121.9731-11-refactormyself@gmail.com>
Date:   Mon,  6 Jul 2020 11:31:20 +0200
From:   Saheed Olayemi Bolarinwa <refactormyself@...il.com>
To:     helgaas@...nel.org
Cc:     Bolarinwa Olayemi Saheed <refactormyself@...il.com>,
        bjorn@...gaas.com, skhan@...uxfoundation.org,
        linux-pci@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 10/11 RFC] PCI/ASPM: Use error return value from pcie_capability_read_*()

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

On failure pcie_capability_read_dword() sets it's last parameter,
val to 0.
However, with Patch 11/11, it is possible that val is set to ~0 on
failure. This would introduce a bug because (x & x) == (~0 & x).

This bug can be avoided if the return value of pcie_capability_read_dword
is checked to confirm success.

Check the return value of pcie_capability_read_dword() to ensure success.

Suggested-by: Bjorn Helgaas <bjorn@...gaas.com>
Signed-off-by: Bolarinwa Olayemi Saheed <refactormyself@...il.com>
---
 drivers/pci/pcie/aspm.c | 33 +++++++++++++++++----------------
 1 file changed, 17 insertions(+), 16 deletions(-)

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index b17e5ffd31b1..32aa9d57672a 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -176,7 +176,7 @@ static void pcie_set_clkpm(struct pcie_link_state *link, int enable)
 
 static void pcie_clkpm_cap_init(struct pcie_link_state *link, int blacklist)
 {
-	int capable = 1, enabled = 1;
+	int ret, capable = 1, enabled = 1;
 	u32 reg32;
 	u16 reg16;
 	struct pci_dev *child;
@@ -184,14 +184,14 @@ static void pcie_clkpm_cap_init(struct pcie_link_state *link, int blacklist)
 
 	/* All functions should have the same cap and state, take the worst */
 	list_for_each_entry(child, &linkbus->devices, bus_list) {
-		pcie_capability_read_dword(child, PCI_EXP_LNKCAP, &reg32);
-		if (!(reg32 & PCI_EXP_LNKCAP_CLKPM)) {
+		ret = pcie_capability_read_dword(child, PCI_EXP_LNKCAP, &reg32);
+		if (ret || !(reg32 & PCI_EXP_LNKCAP_CLKPM)) {
 			capable = 0;
 			enabled = 0;
 			break;
 		}
-		pcie_capability_read_word(child, PCI_EXP_LNKCTL, &reg16);
-		if (!(reg16 & PCI_EXP_LNKCTL_CLKREQ_EN))
+		ret = pcie_capability_read_word(child, PCI_EXP_LNKCTL, &reg16);
+		if (ret || !(reg16 & PCI_EXP_LNKCTL_CLKREQ_EN))
 			enabled = 0;
 	}
 	link->clkpm_enabled = enabled;
@@ -205,6 +205,7 @@ static bool pcie_retrain_link(struct pcie_link_state *link)
 	struct pci_dev *parent = link->pdev;
 	unsigned long end_jiffies;
 	u16 reg16;
+	int ret;
 
 	pcie_capability_read_word(parent, PCI_EXP_LNKCTL, &reg16);
 	reg16 |= PCI_EXP_LNKCTL_RL;
@@ -222,8 +223,8 @@ static bool pcie_retrain_link(struct pcie_link_state *link)
 	/* Wait for link training end. Break out after waiting for timeout */
 	end_jiffies = jiffies + LINK_RETRAIN_TIMEOUT;
 	do {
-		pcie_capability_read_word(parent, PCI_EXP_LNKSTA, &reg16);
-		if (!(reg16 & PCI_EXP_LNKSTA_LT))
+		ret = pcie_capability_read_word(parent, PCI_EXP_LNKSTA, &reg16);
+		if (ret || !(reg16 & PCI_EXP_LNKSTA_LT))
 			break;
 		msleep(1);
 	} while (time_before(jiffies, end_jiffies));
@@ -237,7 +238,7 @@ static bool pcie_retrain_link(struct pcie_link_state *link)
  */
 static void pcie_aspm_configure_common_clock(struct pcie_link_state *link)
 {
-	int same_clock = 1;
+	int ret, same_clock = 1;
 	u16 reg16, parent_reg, child_reg[8];
 	struct pci_dev *child, *parent = link->pdev;
 	struct pci_bus *linkbus = parent->subordinate;
@@ -249,24 +250,24 @@ static void pcie_aspm_configure_common_clock(struct pcie_link_state *link)
 	BUG_ON(!pci_is_pcie(child));
 
 	/* Check downstream component if bit Slot Clock Configuration is 1 */
-	pcie_capability_read_word(child, PCI_EXP_LNKSTA, &reg16);
-	if (!(reg16 & PCI_EXP_LNKSTA_SLC))
+	ret = pcie_capability_read_word(child, PCI_EXP_LNKSTA, &reg16);
+	if (ret || !(reg16 & PCI_EXP_LNKSTA_SLC))
 		same_clock = 0;
 
 	/* Check upstream component if bit Slot Clock Configuration is 1 */
-	pcie_capability_read_word(parent, PCI_EXP_LNKSTA, &reg16);
-	if (!(reg16 & PCI_EXP_LNKSTA_SLC))
+	ret = pcie_capability_read_word(parent, PCI_EXP_LNKSTA, &reg16);
+	if (ret || !(reg16 & PCI_EXP_LNKSTA_SLC))
 		same_clock = 0;
 
 	/* Port might be already in common clock mode */
-	pcie_capability_read_word(parent, PCI_EXP_LNKCTL, &reg16);
-	if (same_clock && (reg16 & PCI_EXP_LNKCTL_CCC)) {
+	ret = pcie_capability_read_word(parent, PCI_EXP_LNKCTL, &reg16);
+	if (!ret && same_clock && (reg16 & PCI_EXP_LNKCTL_CCC)) {
 		bool consistent = true;
 
 		list_for_each_entry(child, &linkbus->devices, bus_list) {
-			pcie_capability_read_word(child, PCI_EXP_LNKCTL,
+			ret = pcie_capability_read_word(child, PCI_EXP_LNKCTL,
 						  &reg16);
-			if (!(reg16 & PCI_EXP_LNKCTL_CCC)) {
+			if (ret || !(reg16 & PCI_EXP_LNKCTL_CCC)) {
 				consistent = false;
 				break;
 			}
-- 
2.18.2