USB: check serial-number string after device reset

This patch (as1048) extends the descriptor checking after a device is
reset.  Now the SerialNumber string descriptor is compared to its old
value, in addition to the device and configuration descriptors.

As a consequence, the kmalloc() call in usb_string() is now on the
error-handling pathway for usb-storage.  Hence its allocation type is
changed to GFO_NOIO.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/Documentation/usb/persist.txt b/Documentation/usb/persist.txt
index bea58db..d56cb1a 100644 (file)
--- a/Documentation/usb/persist.txt
+++ b/Documentation/usb/persist.txt
@@ -136,10 +136,10 @@ aren't guaranteed to be 100% accurate.
 
 If you replace one USB device with another of the same type (same
 manufacturer, same IDs, and so on) there's an excellent chance the
-kernel won't detect the change.  Serial numbers and other strings are
-not compared.  In many cases it wouldn't help if they were, because
-manufacturers frequently omit serial numbers entirely in their
-devices.
+kernel won't detect the change.  The serial number string and other
+descriptors are compared with the kernel's stored values, but this
+might not help since manufacturers frequently omit serial numbers
+entirely in their devices.
 
 Furthermore it's quite possible to leave a USB device exactly the same
 while changing its media.  If you replace the flash memory card in a

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 6dc5899..9fc5179 100644 (file)
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -3010,16 +3010,36 @@ void usb_hub_cleanup(void)
        usb_deregister(&hub_driver);
 } /* usb_hub_cleanup() */
 
-static int config_descriptors_changed(struct usb_device *udev)
-{
-       unsigned                        index;
-       unsigned                        len = 0;
-       struct usb_config_descriptor    *buf;
+static int descriptors_changed(struct usb_device *udev,
+               struct usb_device_descriptor *old_device_descriptor)
+{
+       int             changed = 0;
+       unsigned        index;
+       unsigned        serial_len = 0;
+       unsigned        len;
+       unsigned        old_length;
+       int             length;
+       char            *buf;
+
+       if (memcmp(&udev->descriptor, old_device_descriptor,
+                       sizeof(*old_device_descriptor)) != 0)
+               return 1;
+
+       /* Since the idVendor, idProduct, and bcdDevice values in the
+        * device descriptor haven't changed, we will assume the
+        * Manufacturer and Product strings haven't changed either.
+        * But the SerialNumber string could be different (e.g., a
+        * different flash card of the same brand).
+        */
+       if (udev->serial)
+               serial_len = strlen(udev->serial) + 1;
 
+       len = serial_len;
        for (index = 0; index < udev->descriptor.bNumConfigurations; index++) {
-               if (len < le16_to_cpu(udev->config[index].desc.wTotalLength))
-                       len = le16_to_cpu(udev->config[index].desc.wTotalLength);
+               old_length = le16_to_cpu(udev->config[index].desc.wTotalLength);
+               len = max(len, old_length);
        }
+
        buf = kmalloc(len, GFP_NOIO);
        if (buf == NULL) {
                dev_err(&udev->dev, "no mem to re-read configs after reset\n");
@@ -3027,25 +3047,41 @@ static int config_descriptors_changed(struct usb_device *udev)
                return 1;
        }
        for (index = 0; index < udev->descriptor.bNumConfigurations; index++) {
-               int length;
-               int old_length = le16_to_cpu(udev->config[index].desc.wTotalLength);
-
+               old_length = le16_to_cpu(udev->config[index].desc.wTotalLength);
                length = usb_get_descriptor(udev, USB_DT_CONFIG, index, buf,
                                old_length);
-               if (length < old_length) {
+               if (length != old_length) {
                        dev_dbg(&udev->dev, "config index %d, error %d\n",
                                        index, length);
+                       changed = 1;
                        break;
                }
                if (memcmp (buf, udev->rawdescriptors[index], old_length)
                                != 0) {
                        dev_dbg(&udev->dev, "config index %d changed (#%d)\n",
-                               index, buf->bConfigurationValue);
+                               index,
+                               ((struct usb_config_descriptor *) buf)->
+                                       bConfigurationValue);
+                       changed = 1;
                        break;
                }
        }
+
+       if (!changed && serial_len) {
+               length = usb_string(udev, udev->descriptor.iSerialNumber,
+                               buf, serial_len);
+               if (length + 1 != serial_len) {
+                       dev_dbg(&udev->dev, "serial string error %d\n",
+                                       length);
+                       changed = 1;
+               } else if (memcmp(buf, udev->serial, length) != 0) {
+                       dev_dbg(&udev->dev, "serial string changed\n");
+                       changed = 1;
+               }
+       }
+
        kfree(buf);
-       return index != udev->descriptor.bNumConfigurations;
+       return changed;
 }
 
 /**
@@ -3118,8 +3154,7 @@ int usb_reset_device(struct usb_device *udev)
                goto re_enumerate;
  
        /* Device might have changed firmware (DFU or similar) */
-       if (memcmp(&udev->descriptor, &descriptor, sizeof descriptor)
-                       || config_descriptors_changed (udev)) {
+       if (descriptors_changed(udev, &descriptor)) {
                dev_info(&udev->dev, "device firmware changed\n");
                udev->descriptor = descriptor;  /* for disconnect() calls */
                goto re_enumerate;

diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c
index c311f67..a3695b5 100644 (file)
--- a/drivers/usb/core/message.c
+++ b/drivers/usb/core/message.c
@@ -784,7 +784,7 @@ int usb_string(struct usb_device *dev, int index, char *buf, size_t size)
        if (size <= 0 || !buf || !index)
                return -EINVAL;
        buf[0] = 0;
-       tbuf = kmalloc(256, GFP_KERNEL);
+       tbuf = kmalloc(256, GFP_NOIO);
        if (!tbuf)
                return -ENOMEM;