PCI: Skip Resizable BAR restore on read error

pci_restore_rebar_state() uses the Resizable BAR Control register to decide
how many BARs to restore (nbars) and which BAR each iteration addresses
(bar_idx).

When a device does not respond, config reads typically return
PCI_ERROR_RESPONSE (~0).  Both fields are 3 bits wide, so nbars and bar_idx
both evaluate to 7, past the spec's valid ranges for both fields.
pci_resource_n() then returns an unrelated resource slot, whose size is
used to derive a nonsensical value written back to the Resizable BAR
Control register.

Bail out if any Resizable BAR Control read returns PCI_ERROR_RESPONSE. No
further BARs are touched, which is safe because a config read that returns
PCI_ERROR_RESPONSE indicates the device is unreachable and restoration is
pointless.

Fixes: d3252ace0bc6 ("PCI: Restore resized BAR state on resume")
Signed-off-by: Marco Nenciarini <mnencia@kcore.it>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/666cac19b5daa0ab0e0ab64454e76b4d24465dbd.1776429882.git.mnencia@kcore.it

diff --git a/drivers/pci/rebar.c b/drivers/pci/rebar.c
index 39f8cf3b70d5728cd76f5ab504ee43aad011c8b6..11965947c4cb5bbf4ce194e758d74c828ae85053 100644 (file)
--- a/drivers/pci/rebar.c
+++ b/drivers/pci/rebar.c
@@ -231,6 +231,9 @@ void pci_restore_rebar_state(struct pci_dev *pdev)
                return;
 
        pci_read_config_dword(pdev, pos + PCI_REBAR_CTRL, &ctrl);
+       if (PCI_POSSIBLE_ERROR(ctrl))
+               return;
+
        nbars = FIELD_GET(PCI_REBAR_CTRL_NBAR_MASK, ctrl);
 
        for (i = 0; i < nbars; i++, pos += 8) {
@@ -238,6 +241,9 @@ void pci_restore_rebar_state(struct pci_dev *pdev)
                int bar_idx, size;
 
                pci_read_config_dword(pdev, pos + PCI_REBAR_CTRL, &ctrl);
+               if (PCI_POSSIBLE_ERROR(ctrl))
+                       return;
+
                bar_idx = ctrl & PCI_REBAR_CTRL_BAR_IDX;
                res = pci_resource_n(pdev, bar_idx);
                size = pci_rebar_bytes_to_size(resource_size(res));