xhci: harden xhci_find_next_ext_cap against device removal

xhci_find_next_ext_cap doesn't check for PCI hotplug removal and may use
the PCI master abort bit pattern (~0) to calculate a new PCI address
offset to read/write.  The has lead to reproducable crashes when testing
surprise removal during device initialization on a Stratus platform, at
least after commit d5ddcdf4d672 ("xhci: rework xhci extended capability
list parsing functions").

The crash is repeatable on a Stratus platform when injecting hardware
faults to induce xHCI host controller hotplug during driver
initialization.  If a PCI read in xhci_find_next_ext_cap returns the
master abort pattern, quirk_usb_handoff_xhci may start using a bogus
ext_cap_offset to start searching more bogus PCI addresses.

Signed-off-by: Joe Lawrence <joe.lawrence@stratus.com>
Acked-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/host/xhci-ext-caps.h b/drivers/usb/host/xhci-ext-caps.h
index 04ce6b156b350e5dd0f9f9a321c79eb4d173b656..e0244fb3903dc85287f509bbac97600734c9b5af 100644 (file)
--- a/drivers/usb/host/xhci-ext-caps.h
+++ b/drivers/usb/host/xhci-ext-caps.h
@@ -112,12 +112,16 @@ static inline int xhci_find_next_ext_cap(void __iomem *base, u32 start, int id)
        offset = start;
        if (!start || start == XHCI_HCC_PARAMS_OFFSET) {
                val = readl(base + XHCI_HCC_PARAMS_OFFSET);
+               if (val == ~0)
+                       return 0;
                offset = XHCI_HCC_EXT_CAPS(val) << 2;
                if (!offset)
                        return 0;
        };
        do {
                val = readl(base + offset);
+               if (val == ~0)
+                       return 0;
                if (XHCI_EXT_CAPS_ID(val) == id && offset != start)
                        return offset;