From aed9d65ac3278d4febd8665bd7db59ef53e825fe Mon Sep 17 00:00:00 2001 From: Alan Stern Date: Mon, 1 Aug 2016 15:25:56 -0400 Subject: [PATCH] USB: validate wMaxPacketValue entries in endpoint descriptors Erroneous or malicious endpoint descriptors may have non-zero bits in reserved positions, or out-of-bounds values. This patch helps prevent these from causing problems by bounds-checking the wMaxPacketValue entries in endpoint descriptors and capping the values at the maximum allowed. This issue was first discovered and tests were conducted by Jake Lamberson , an intern working for Rosie Hall. Signed-off-by: Alan Stern Reported-by: roswest Tested-by: roswest CC: Signed-off-by: Greg Kroah-Hartman --- drivers/usb/core/config.c | 66 +++++++++++++++++++++++++++++++++++++-- 1 file changed, 63 insertions(+), 3 deletions(-) diff --git a/drivers/usb/core/config.c b/drivers/usb/core/config.c index 31ccdccd7a04..051163189810 100644 --- a/drivers/usb/core/config.c +++ b/drivers/usb/core/config.c @@ -171,6 +171,31 @@ static void usb_parse_ss_endpoint_companion(struct device *ddev, int cfgno, ep, buffer, size); } +static const unsigned short low_speed_maxpacket_maxes[4] = { + [USB_ENDPOINT_XFER_CONTROL] = 8, + [USB_ENDPOINT_XFER_ISOC] = 0, + [USB_ENDPOINT_XFER_BULK] = 0, + [USB_ENDPOINT_XFER_INT] = 8, +}; +static const unsigned short full_speed_maxpacket_maxes[4] = { + [USB_ENDPOINT_XFER_CONTROL] = 64, + [USB_ENDPOINT_XFER_ISOC] = 1023, + [USB_ENDPOINT_XFER_BULK] = 64, + [USB_ENDPOINT_XFER_INT] = 64, +}; +static const unsigned short high_speed_maxpacket_maxes[4] = { + [USB_ENDPOINT_XFER_CONTROL] = 64, + [USB_ENDPOINT_XFER_ISOC] = 1024, + [USB_ENDPOINT_XFER_BULK] = 512, + [USB_ENDPOINT_XFER_INT] = 1023, +}; +static const unsigned short super_speed_maxpacket_maxes[4] = { + [USB_ENDPOINT_XFER_CONTROL] = 512, + [USB_ENDPOINT_XFER_ISOC] = 1024, + [USB_ENDPOINT_XFER_BULK] = 1024, + [USB_ENDPOINT_XFER_INT] = 1024, +}; + static int usb_parse_endpoint(struct device *ddev, int cfgno, int inum, int asnum, struct usb_host_interface *ifp, int num_ep, unsigned char *buffer, int size) @@ -179,6 +204,8 @@ static int usb_parse_endpoint(struct device *ddev, int cfgno, int inum, struct usb_endpoint_descriptor *d; struct usb_host_endpoint *endpoint; int n, i, j, retval; + unsigned int maxp; + const unsigned short *maxpacket_maxes; d = (struct usb_endpoint_descriptor *) buffer; buffer += d->bLength; @@ -286,6 +313,42 @@ static int usb_parse_endpoint(struct device *ddev, int cfgno, int inum, endpoint->desc.wMaxPacketSize = cpu_to_le16(8); } + /* Validate the wMaxPacketSize field */ + maxp = usb_endpoint_maxp(&endpoint->desc); + + /* Find the highest legal maxpacket size for this endpoint */ + i = 0; /* additional transactions per microframe */ + switch (to_usb_device(ddev)->speed) { + case USB_SPEED_LOW: + maxpacket_maxes = low_speed_maxpacket_maxes; + break; + case USB_SPEED_FULL: + maxpacket_maxes = full_speed_maxpacket_maxes; + break; + case USB_SPEED_HIGH: + /* Bits 12..11 are allowed only for HS periodic endpoints */ + if (usb_endpoint_xfer_int(d) || usb_endpoint_xfer_isoc(d)) { + i = maxp & (BIT(12) | BIT(11)); + maxp &= ~i; + } + /* fallthrough */ + default: + maxpacket_maxes = high_speed_maxpacket_maxes; + break; + case USB_SPEED_SUPER: + case USB_SPEED_SUPER_PLUS: + maxpacket_maxes = super_speed_maxpacket_maxes; + break; + } + j = maxpacket_maxes[usb_endpoint_type(&endpoint->desc)]; + + if (maxp > j) { + dev_warn(ddev, "config %d interface %d altsetting %d endpoint 0x%X has invalid maxpacket %d, setting to %d\n", + cfgno, inum, asnum, d->bEndpointAddress, maxp, j); + maxp = j; + endpoint->desc.wMaxPacketSize = cpu_to_le16(i | maxp); + } + /* * Some buggy high speed devices have bulk endpoints using * maxpacket sizes other than 512. High speed HCDs may not @@ -293,9 +356,6 @@ static int usb_parse_endpoint(struct device *ddev, int cfgno, int inum, */ if (to_usb_device(ddev)->speed == USB_SPEED_HIGH && usb_endpoint_xfer_bulk(d)) { - unsigned maxp; - - maxp = usb_endpoint_maxp(&endpoint->desc) & 0x07ff; if (maxp != 512) dev_warn(ddev, "config %d interface %d altsetting %d " "bulk endpoint 0x%X has invalid maxpacket %d\n", -- 2.20.1