[PATCH] USB: core: limit access to rawdescriptors which were not allocated

[yanfei.xu]

From: Yanfei Xu <yanfei...@windriver.com>

When using systemcall to read the rawdescriptors, make sure we won't
access to the rawdescriptors never allocated, which are number
exceed the USB_MAXCONFIG.

Reported-by: syzbot+256e56ddde8b8957e...@syzkaller.appspotmail.com
Signed-off-by: Yanfei Xu <yanfei...@windriver.com>
---
 drivers/usb/core/sysfs.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/core/sysfs.c b/drivers/usb/core/sysfs.c
index a2ca38e25e0c..1a7a625e5f55 100644
--- a/drivers/usb/core/sysfs.c
+++ b/drivers/usb/core/sysfs.c
@@ -895,7 +895,8 @@ read_descriptors(struct file *filp, struct kobject *kobj,
         * configurations (config plus subsidiary descriptors).
         */
        for (cfgno = -1; cfgno < udev->descriptor.bNumConfigurations &&
-                       nleft > 0; ++cfgno) {
+                       nleft > 0 &&
+                       cfgno < USB_MAXCONFIG; ++cfgno) {
                if (cfgno < 0) {
                        src = &udev->descriptor;
                        srclen = sizeof(struct usb_device_descriptor);
-- 
2.18.2