On Tue, Dec 12, 2017 at 4:41 PM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
> On Mon, 11 Dec 2017, Greg KH wrote:
>
>> From: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
>>
>> When cleaning up the configurations, make sure we only free the number
>> of configurations and interfaces that we could have allocated.
>>
>> Reported-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
>> Cc: stable <stable@xxxxxxxxxxxxxxx>
>> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
>>
>> diff --git a/drivers/usb/core/config.c b/drivers/usb/core/config.c
>> index 55b198ba629b..93b38471754e 100644
>> --- a/drivers/usb/core/config.c
>> +++ b/drivers/usb/core/config.c
>> @@ -764,18 +764,21 @@ void usb_destroy_configuration(struct usb_device *dev)
>> return;
>>
>> if (dev->rawdescriptors) {
>> - for (i = 0; i < dev->descriptor.bNumConfigurations; i++)
>> + for (i = 0; i < dev->descriptor.bNumConfigurations &&
>> + i < USB_MAXCONFIG; i++)
>> kfree(dev->rawdescriptors[i]);
>>
>> kfree(dev->rawdescriptors);
>> dev->rawdescriptors = NULL;
>> }
>>
>> - for (c = 0; c < dev->descriptor.bNumConfigurations; c++) {
>> + for (c = 0; c < dev->descriptor.bNumConfigurations &&
>> + c < USB_MAXCONFIG; c++) {
>> struct usb_host_config *cf = &dev->config[c];
>>
>> kfree(cf->string);
>> - for (i = 0; i < cf->desc.bNumInterfaces; i++) {
>> + for (i = 0; i < cf->desc.bNumInterfaces &&
>> + i < USB_MAXINTERFACES; i++) {
>> if (cf->intf_cache[i])
>> kref_put(&cf->intf_cache[i]->ref,
>> usb_release_interface_cache);
>
> None of these changes are necessary. The code is careful to reduce
> dev->descriptor.bNumConfigurations and config->desc.bNumInterfaces when
> necessary.
>
> In usb_get_configuration() (line 806 on my system):
>
> if (ncfg > USB_MAXCONFIG) {
> dev_warn(ddev, "too many configurations: %d, "
> "using maximum allowed: %d\n", ncfg, USB_MAXCONFIG);
> dev->descriptor.bNumConfigurations = ncfg = USB_MAXCONFIG;
> }
>
> In usb_parse_configuration() (line 676 on my system):
>
> if (n != nintf)
> dev_warn(ddev, "config %d has %d interface%s, different from "
> "the descriptor's value: %d\n",
> cfgno, n, plural(n), nintf_orig);
> else if (n == 0)
> dev_warn(ddev, "config %d has no interfaces?\n", cfgno);
> config->desc.bNumInterfaces = nintf = n;
usb_parse_configuration() might return before reducing
config->desc.bNumInterfaces, and usb_destroy_configuration() is still
called in this case.
>
> Alan Stern
>
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