From 1c069b057dcf64fada952eaa868d35f02bb0cfc2 Mon Sep 17 00:00:00 2001 From: Alan Stern Date: Fri, 9 Dec 2016 15:24:24 -0500 Subject: [PATCH] USB: gadgetfs: fix checks of wTotalLength in config descriptors Andrey Konovalov's fuzz testing of gadgetfs showed that we should improve the driver's checks for valid configuration descriptors passed in by the user. In particular, the driver needs to verify that the wTotalLength value in the descriptor is not too short (smaller than USB_DT_CONFIG_SIZE). And the check for whether wTotalLength is too large has to be changed, because the driver assumes there is always enough room remaining in the buffer to hold a device descriptor (at least USB_DT_DEVICE_SIZE bytes). This patch adds the additional check and fixes the existing check. It may do a little more than strictly necessary, but one extra check won't hurt. Signed-off-by: Alan Stern CC: Andrey Konovalov CC: Signed-off-by: Felipe Balbi --- drivers/usb/gadget/legacy/inode.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/drivers/usb/gadget/legacy/inode.c b/drivers/usb/gadget/legacy/inode.c index f1ca339426073..08e5ecc050795 100644 --- a/drivers/usb/gadget/legacy/inode.c +++ b/drivers/usb/gadget/legacy/inode.c @@ -1734,10 +1734,12 @@ static struct usb_gadget_driver gadgetfs_driver = { * such as configuration notifications. */ -static int is_valid_config (struct usb_config_descriptor *config) +static int is_valid_config(struct usb_config_descriptor *config, + unsigned int total) { return config->bDescriptorType == USB_DT_CONFIG && config->bLength == USB_DT_CONFIG_SIZE + && total >= USB_DT_CONFIG_SIZE && config->bConfigurationValue != 0 && (config->bmAttributes & USB_CONFIG_ATT_ONE) != 0 && (config->bmAttributes & USB_CONFIG_ATT_WAKEUP) == 0; @@ -1787,7 +1789,8 @@ dev_config (struct file *fd, const char __user *buf, size_t len, loff_t *ptr) /* full or low speed config */ dev->config = (void *) kbuf; total = le16_to_cpu(dev->config->wTotalLength); - if (!is_valid_config (dev->config) || total >= length) + if (!is_valid_config(dev->config, total) || + total > length - USB_DT_DEVICE_SIZE) goto fail; kbuf += total; length -= total; @@ -1796,7 +1799,8 @@ dev_config (struct file *fd, const char __user *buf, size_t len, loff_t *ptr) if (kbuf [1] == USB_DT_CONFIG) { dev->hs_config = (void *) kbuf; total = le16_to_cpu(dev->hs_config->wTotalLength); - if (!is_valid_config (dev->hs_config) || total >= length) + if (!is_valid_config(dev->hs_config, total) || + total > length - USB_DT_DEVICE_SIZE) goto fail; kbuf += total; length -= total;