Re: [Linux-kernel-mentees] [PATCH 11/14 v3] PCI/PM: Check return value of pcie_capability_read_*()

From: Saheed Olayemi Bolarinwa
Sent: 10 July 2020 22:20
To: helgaas@kernel.org
From: Bolarinwa Olayemi Saheed <redacted>

On failure pcie_capability_read_dword() sets it's last parameter,
val to 0.
However, with Patch 14/14, 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 <redacted>
Signed-off-by: Bolarinwa Olayemi Saheed <redacted>
---
 drivers/pci/pci.c | 52 ++++++++++++++++++++++++++++++-----------------
 1 file changed, 33 insertions(+), 19 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index ce096272f52b..9f18ffbf7bd4 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c

@@ -3207,6 +3207,7 @@ void pci_configure_ari(struct pci_dev *dev)
 {
 	u32 cap;
 	struct pci_dev *bridge;
+	int ret;

 	if (pcie_ari_disabled || !pci_is_pcie(dev) || dev->devfn)
 		return;

@@ -3215,8 +3216,8 @@ void pci_configure_ari(struct pci_dev *dev)
 	if (!bridge)
 		return;

-	pcie_capability_read_dword(bridge, PCI_EXP_DEVCAP2, &cap);
-	if (!(cap & PCI_EXP_DEVCAP2_ARI))
+	ret = pcie_capability_read_dword(bridge, PCI_EXP_DEVCAP2, &cap);
+	if (ret || !(cap & PCI_EXP_DEVCAP2_ARI))
 		return;