HID: keep dev_rdesc unmodified and use it for comparisons

The dev_rdesc member of the hid_device structure is meant to store the original
report descriptor received from the device, but it is currently passed to any
report_fixup method before it is copied to the rdesc member. This patch uses a
temporary buffer to shield dev_rdesc from the side effects of many HID drivers'
report_fixup implementations.

usbhid's hid_post_reset checks the report descriptor currently returned by the
device against a descriptor that may have been modified by a driver's
report_fixup method. That leaves some devices nonfunctional after a resume, with
a "reset_resume error 1" reported. This patch checks the new descriptor against
the unmodified dev_rdesc instead and uses the original, instead of modified,
report size.

BugLink: http://bugs.launchpad.net/bugs/1049623
Signed-off-by: Kevin Daughtridge <kevin@kdau.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

2 files changed, 16 insertions, 6 deletions

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index dd679a582c2..ec917690c26 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -757,6 +757,7 @@ int hid_open_report(struct hid_device *device)
         struct hid_item item;
         unsigned int size;
         __u8 *start;
+        __u8 *buf;
         __u8 *end;
         int ret;
         static int (*dispatch_type[])(struct hid_parser *parser,
@@ -775,12 +776,21 @@ int hid_open_report(struct hid_device *device)
                 return -ENODEV;
         size = device->dev_rsize;
 
+        buf = kmemdup(start, size, GFP_KERNEL);
+        if (buf == NULL)
+                return -ENOMEM;
+
         if (device->driver->report_fixup)
-                start = device->driver->report_fixup(device, start, &size);
+                start = device->driver->report_fixup(device, buf, &size);
+        else
+                start = buf;
 
-        device->rdesc = kmemdup(start, size, GFP_KERNEL);
-        if (device->rdesc == NULL)
+        start = kmemdup(start, size, GFP_KERNEL);
+        kfree(buf);
+        if (start == NULL)
                 return -ENOMEM;
+
+        device->rdesc = start;
         device->rsize = size;
 
         parser = vzalloc(sizeof(struct hid_parser));
diff --git a/drivers/hid/usbhid/hid-core.c b/drivers/hid/usbhid/hid-core.c
index dedd8e4e5c6..8e0c4bf94eb 100644
--- a/drivers/hid/usbhid/hid-core.c
+++ b/drivers/hid/usbhid/hid-core.c
@@ -1415,20 +1415,20 @@ static int hid_post_reset(struct usb_interface *intf)
          * configuration descriptors passed, we already know that
          * the size of the HID report descriptor has not changed.
          */
-        rdesc = kmalloc(hid->rsize, GFP_KERNEL);
+        rdesc = kmalloc(hid->dev_rsize, GFP_KERNEL);
         if (!rdesc) {
                 dbg_hid("couldn't allocate rdesc memory (post_reset)\n");
                 return 1;
         }
         status = hid_get_class_descriptor(dev,
                                 interface->desc.bInterfaceNumber,
-                                HID_DT_REPORT, rdesc, hid->rsize);
+                                HID_DT_REPORT, rdesc, hid->dev_rsize);
         if (status < 0) {
                 dbg_hid("reading report descriptor failed (post_reset)\n");
                 kfree(rdesc);
                 return 1;
         }
-        status = memcmp(rdesc, hid->rdesc, hid->rsize);
+        status = memcmp(rdesc, hid->dev_rdesc, hid->dev_rsize);
         kfree(rdesc);
         if (status != 0) {
                 dbg_hid("report descriptor changed\n");