xen/pciback: Fix conf_space read/write overlap check.

Current overlap check is evaluating to false a case where a filter
field is fully contained (proper subset) of a r/w request.  This
change applies classical overlap check instead to include all the
scenarios.

More specifically, for (Hilscher GmbH CIFX 50E-DP(M/S)) device driver
the logic is such that the entire confspace is read and written in 4
byte chunks. In this case as an example, CACHE_LINE_SIZE,
LATENCY_TIMER and PCI_BIST are arriving together in one call to
xen_pcibk_config_write() with offset == 0xc and size == 4.  With the
exsisting overlap check the LATENCY_TIMER field (offset == 0xd, length
== 1) is fully contained in the write request and hence is excluded
from write, which is incorrect.

Signed-off-by: Andrey Grodzovsky <andrey2805@gmail.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Jan Beulich <JBeulich@suse.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

diff --git a/drivers/xen/xen-pciback/conf_space.c b/drivers/xen/xen-pciback/conf_space.c
index 8e67336f8ddd238d7763a118bb460327ba3278f7..6a25533da237db612f2bb4a99096a96fd49c0d8c 100644 (file)
--- a/drivers/xen/xen-pciback/conf_space.c
+++ b/drivers/xen/xen-pciback/conf_space.c
@@ -183,8 +183,7 @@ int xen_pcibk_config_read(struct pci_dev *dev, int offset, int size,
                field_start = OFFSET(cfg_entry);
                field_end = OFFSET(cfg_entry) + field->size;
 
-               if ((req_start >= field_start && req_start < field_end)
-                   || (req_end > field_start && req_end <= field_end)) {
+                if (req_end > field_start && field_end > req_start) {
                        err = conf_space_read(dev, cfg_entry, field_start,
                                              &tmp_val);
                        if (err)
@@ -230,8 +229,7 @@ int xen_pcibk_config_write(struct pci_dev *dev, int offset, int size, u32 value)
                field_start = OFFSET(cfg_entry);
                field_end = OFFSET(cfg_entry) + field->size;
 
-               if ((req_start >= field_start && req_start < field_end)
-                   || (req_end > field_start && req_end <= field_end)) {
+                if (req_end > field_start && field_end > req_start) {
                        tmp_val = 0;
 
                        err = xen_pcibk_config_read(dev, field_start,