xen-pciback: reject out of range inputs

This add checks for out of range numbers (including in cases where the
folding of slot and function into a single value could yield false
matches).

It also removes the bogus field width restrictions in str_to_quirk() -
nowhere else in the driver this is being done, and hence this function
could reject input the equivalent of which would be happily accepted
in other places (in particular, "0x" prefixes causing the effective
width of the actual number to be either zero or less than what would be
required to cover the full range of valid values). Note that for the
moment this second part is cosmetic only, as the kernel's sscanf()
currently ignores the field widths, but a patch to overcome this is on
its way.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

---
 drivers/xen/xen-pciback/pci_stub.c |   39 +++++++++++++++++++++++++------------
 1 file changed, 27 insertions(+), 12 deletions(-)

--- 3.7-rc3-xen-pciback.orig/drivers/xen/xen-pciback/pci_stub.c
+++ 3.7-rc3-xen-pciback/drivers/xen/xen-pciback/pci_stub.c
@@ -142,7 +142,8 @@ static struct pcistub_device *pcistub_de
 		if (psdev->dev != NULL
 		    && domain == pci_domain_nr(psdev->dev->bus)
 		    && bus == psdev->dev->bus->number
-		    && PCI_DEVFN(slot, func) == psdev->dev->devfn) {
+		    && slot == PCI_SLOT(psdev->dev->devfn)
+		    && func == PCI_FUNC(psdev->dev->devfn)) {
 			pcistub_device_get(psdev);
 			goto out;
 		}
@@ -191,7 +192,8 @@ struct pci_dev *pcistub_get_pci_dev_by_s
 		if (psdev->dev != NULL
 		    && domain == pci_domain_nr(psdev->dev->bus)
 		    && bus == psdev->dev->bus->number
-		    && PCI_DEVFN(slot, func) == psdev->dev->devfn) {
+		    && slot == PCI_SLOT(psdev->dev->devfn)
+		    && func == PCI_FUNC(psdev->dev->devfn)) {
 			found_dev = pcistub_device_get_pci_dev(pdev, psdev);
 			break;
 		}
@@ -936,14 +938,14 @@ static inline int str_to_quirk(const cha
 {
 	int parsed = 0;
 
-	sscanf(buf, " %4x:%2x:%2x.%d-%8x:%1x:%8x %n", domain, bus, slot, func,
+	sscanf(buf, " %x:%x:%x.%x-%x:%x:%x %n", domain, bus, slot, func,
 	       reg, size, mask, &parsed);
 	if (parsed && !buf[parsed])
 		return 0;
 
 	/* try again without domain */
 	*domain = 0;
-	sscanf(buf, " %2x:%2x.%d-%8x:%1x:%8x %n", bus, slot, func, reg, size,
+	sscanf(buf, " %x:%x.%x-%x:%x:%x %n", bus, slot, func, reg, size,
 	       mask, &parsed);
 	if (parsed && !buf[parsed])
 		return 0;
@@ -955,7 +957,7 @@ static int pcistub_device_id_add(int dom
 {
 	struct pcistub_device_id *pci_dev_id;
 	unsigned long flags;
-	int rc = 0;
+	int rc = 0, devfn = PCI_DEVFN(slot, func);
 
 	if (slot < 0) {
 		for (slot = 0; !rc && slot < 32; ++slot)
@@ -969,13 +971,24 @@ static int pcistub_device_id_add(int dom
 		return rc;
 	}
 
+	if ((
+#if !defined(MODULE) /* pci_domains_supported is not being exported */ \
+    || !defined(CONFIG_PCI_DOMAINS)
+	     !pci_domains_supported ? domain :
+#endif
+	     domain < 0 || domain > 0xffff)
+	    || bus < 0 || bus > 0xff
+	    || PCI_SLOT(devfn) != slot
+	    || PCI_FUNC(devfn) != func)
+		return -EINVAL;
+
 	pci_dev_id = kmalloc(sizeof(*pci_dev_id), GFP_KERNEL);
 	if (!pci_dev_id)
 		return -ENOMEM;
 
 	pci_dev_id->domain = domain;
 	pci_dev_id->bus = bus;
-	pci_dev_id->devfn = PCI_DEVFN(slot, func);
+	pci_dev_id->devfn = devfn;
 
 	pr_debug(DRV_NAME ": wants to seize %04x:%02x:%02x.%d\n",
 		 domain, bus, slot, func);
@@ -1016,14 +1029,18 @@ static int pcistub_device_id_remove(int
 	return err;
 }
 
-static int pcistub_reg_add(int domain, int bus, int slot, int func, int reg,
-			   int size, int mask)
+static int pcistub_reg_add(int domain, int bus, int slot, int func,
+			   unsigned int reg, unsigned int size,
+			   unsigned int mask)
 {
 	int err = 0;
 	struct pcistub_device *psdev;
 	struct pci_dev *dev;
 	struct config_field *field;
 
+	if (reg > 0xfff || (size < 4 && (mask >> (size * 8))))
+		return -EINVAL;
+
 	psdev = pcistub_device_find(domain, bus, slot, func);
 	if (!psdev) {
 		err = -ENODEV;
@@ -1254,13 +1271,11 @@ static ssize_t permissive_add(struct dev
 	int err;
 	struct pcistub_device *psdev;
 	struct xen_pcibk_dev_data *dev_data;
+
 	err = str_to_slot(buf, &domain, &bus, &slot, &func);
 	if (err)
 		goto out;
-	if (slot < 0 || func < 0) {
-		err = -EINVAL;
-		goto out;
-	}
+
 	psdev = pcistub_device_find(domain, bus, slot, func);
 	if (!psdev) {
 		err = -ENODEV;