linux-kernel - [PATCH v4 08/12] PCI: Check if pcie_capability_read

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Message-Id: <20200731114329.100848-1-refactormyself@gmail.com>
Date:   Fri, 31 Jul 2020 13:43:25 +0200
From:   "Saheed O. Bolarinwa" <refactormyself@...il.com>
To:     helgaas@...nel.org
Cc:     "Saheed O. Bolarinwa" <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 v4 08/12] PCI: Check if pcie_capability_read_*() reads ~0

On failure pcie_capability_read_*() sets it's last parameter, val
to 0. However, with Patch 12/12, it is possible that val is set
to ~0 on failure. This would introduce a bug because
(x & x) == (~0 & x).

Since ~0 is an invalid value in here,

Add extra check for ~0 in the if condition to ensure success or
failure.

Suggested-by: Bjorn Helgaas <bjorn@...gaas.com>
Signed-off-by: Saheed O. Bolarinwa <refactormyself@...il.com>
---
 drivers/pci/probe.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 2f66988cea25..af95f67c19a7 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1124,7 +1124,7 @@ static void pci_enable_crs(struct pci_dev *pdev)
 
 	/* Enable CRS Software Visibility if supported */
 	pcie_capability_read_word(pdev, PCI_EXP_RTCAP, &root_cap);
-	if (root_cap & PCI_EXP_RTCAP_CRSVIS)
+	if ((root_cap != (u16)~0) && (root_cap & PCI_EXP_RTCAP_CRSVIS))
 		pcie_capability_set_word(pdev, PCI_EXP_RTCTL,
 					 PCI_EXP_RTCTL_CRSSVE);
 }
@@ -1521,7 +1521,7 @@ void set_pcie_hotplug_bridge(struct pci_dev *pdev)
 	u32 reg32;
 
 	pcie_capability_read_dword(pdev, PCI_EXP_SLTCAP, &reg32);
-	if (reg32 & PCI_EXP_SLTCAP_HPC)
+	if ((reg32 != (u32)~0) && (reg32 & PCI_EXP_SLTCAP_HPC))
 		pdev->is_hotplug_bridge = 1;
 }
 
@@ -2060,7 +2060,7 @@ bool pcie_relaxed_ordering_enabled(struct pci_dev *dev)
 
 	pcie_capability_read_word(dev, PCI_EXP_DEVCTL, &v);
 
-	return !!(v & PCI_EXP_DEVCTL_RELAX_EN);
+	return ((v != (u16)~0) && (v & PCI_EXP_DEVCTL_RELAX_EN));
 }
 EXPORT_SYMBOL(pcie_relaxed_ordering_enabled);
 
@@ -2101,11 +2101,11 @@ static void pci_configure_ltr(struct pci_dev *dev)
 		return;
 
 	pcie_capability_read_dword(dev, PCI_EXP_DEVCAP2, &cap);
-	if (!(cap & PCI_EXP_DEVCAP2_LTR))
+	if ((cap == (u32)~0) || !(cap & PCI_EXP_DEVCAP2_LTR))
 		return;
 
 	pcie_capability_read_dword(dev, PCI_EXP_DEVCTL2, &ctl);
-	if (ctl & PCI_EXP_DEVCTL2_LTR_EN) {
+	if ((ctl != (u32)~0) && (ctl & PCI_EXP_DEVCTL2_LTR_EN)) {
 		if (pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT) {
 			dev->ltr_path = 1;
 			return;
@@ -2147,7 +2147,7 @@ static void pci_configure_eetlp_prefix(struct pci_dev *dev)
 		return;
 
 	pcie_capability_read_dword(dev, PCI_EXP_DEVCAP2, &cap);
-	if (!(cap & PCI_EXP_DEVCAP2_EE_PREFIX))
+	if ((cap == (u32)~0) || !(cap & PCI_EXP_DEVCAP2_EE_PREFIX))
 		return;
 
 	pcie_type = pci_pcie_type(dev);
-- 
2.18.4