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    Subject[PATCH 5/6] USB: check serial-number string after device reset
    Date
    From: Alan Stern <stern@rowland.harvard.edu>

    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>
    ---
    Documentation/usb/persist.txt | 8 ++--
    drivers/usb/core/hub.c | 65 +++++++++++++++++++++++++++++++---------
    drivers/usb/core/message.c | 2 +-
    3 files changed, 55 insertions(+), 20 deletions(-)

    diff --git a/Documentation/usb/persist.txt b/Documentation/usb/persist.txt
    index bea58db..d56cb1a 100644
    --- 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 277d4ec..545fa72 100644
    --- a/drivers/usb/core/hub.c
    +++ b/drivers/usb/core/hub.c
    @@ -3011,16 +3011,36 @@ 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");
    @@ -3028,25 +3048,41 @@ 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;
    }

    /**
    @@ -3119,8 +3155,7 @@ 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 fefb922..a45076e 100644
    --- 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;

    --
    1.5.4.3


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