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>

1 files changed, 13 insertions, 3 deletions

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index dd679a582c2c..ec917690c263 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));