[PATCH 7/14 v3] PCI: pciehp: Check the return value of pcie_capability_read_*()

Saheed Olayemi Bolarinwa
2020-07-10T22:20:25Z

If pcie_capability_read_word() fail, slot_ctrl will be 0 and the switch
expression evaluates to 0. So *status = 1 "ON". However, with Patch 14/14
it is possible that slot_ctrl is set to ~0 on failure. This would
introduce a bug because (x & x) == (~0 & x), so the switch expression
evaluates to PCI_EXP_SLTCTL_PCC. This means that on failure *status = 1
"OFF", since PCI_EXP_SLTCTL_PCC = PCI_EXP_SLTCTL_PWR_OFF.

Use an if-statement and include a check on the return value of
pcie_capability_read_word() to confirm success or failure.

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

---
drivers/pci/hotplug/pciehp_hpc.c | 14 +++++---------
1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
index b89c9ee4a3b5..f5ef3fbace69 100644
--- a/drivers/pci/hotplug/pciehp_hpc.c
+++ b/drivers/pci/hotplug/pciehp_hpc.c
@@ -394,20 +394,16 @@ void pciehp_get_power_status(struct controller *ctrl, u8 *status)
{
struct pci_dev *pdev = ctrl_dev(ctrl);
u16 slot_ctrl;
+ int ret;

- pcie_capability_read_word(pdev, PCI_EXP_SLTCTL, &slot_ctrl);
+ *status = 1; /* On */
+ ret = pcie_capability_read_word(pdev, PCI_EXP_SLTCTL, &slot_ctrl);
ctrl_dbg(ctrl, "%s: SLOTCTRL %x value read %x\n", __func__,
pci_pcie_cap(ctrl->pcie->port) + PCI_EXP_SLTCTL, slot_ctrl);

- switch (slot_ctrl & PCI_EXP_SLTCTL_PCC) {
- case PCI_EXP_SLTCTL_PWR_OFF:
+ if (!ret &&
+ ((slot_ctrl & PCI_EXP_SLTCTL_PCC) == PCI_EXP_SLTCTL_PWR_OFF))
*status = 0; /* Off */
- break;
- case PCI_EXP_SLTCTL_PWR_ON:
- default:
- *status = 1; /* On */
- break;
- }
}

void pciehp_get_latch_status(struct controller *ctrl, u8 *status)
--
2.18.2