CVE-2017-8070: Improper Restriction of Operations within the Bounds of a Memory Buffer (CWE-119)
value: drivers/net/usb/catc.c in the Linux kernel 4.9.x before 4.9.11 interacts incorrectly with the CONFIG_VMAP_STACK option, which allows local users to cause a denial of service (system crash or memory corruption) or possibly have unspecified other impact by leveraging use of more than one virtual page for a DMA scatterlist.
CWE description: The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.
CVSS v3 base score: 7.8
Published: 2017-04-23T05:59Z
Repository: https://github.com/torvalds/linux
Language: C
Files changed: drivers/net/usb/catc.c
Commit date: 2017-02-07 10:07:02 -0500
Commit message: catc: Use heap buffer for memory size test

Allocating USB buffers on the stack is not portable, and no longer
works on x86_64 (with VMAP_STACK enabled as per default).

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

Diff: diff --git a/drivers/net/usb/catc.c b/drivers/net/usb/catc.c
index 985909eab72c..0acc9b640419 100644
--- a/drivers/net/usb/catc.c
+++ b/drivers/net/usb/catc.c
@@ -774,11 +774,11 @@ static int catc_probe(struct usb_interface *intf, const struct usb_device_id *id
 	struct device *dev = &intf->dev;
 	struct usb_device *usbdev = interface_to_usbdev(intf);
 	struct net_device *netdev;
 	struct catc *catc;
 	u8 broadcast[ETH_ALEN];
-	int i, pktsz, ret;
+	int pktsz, ret;
 
 	if (usb_set_interface(usbdev,
 			intf->altsetting->desc.bInterfaceNumber, 1)) {
 		dev_err(dev, "Can't set altsetting 1.\n");
 		return -EIO;
@@ -838,19 +838,28 @@ static int catc_probe(struct usb_interface *intf, const struct usb_device_id *id
 
 	usb_fill_int_urb(catc->irq_urb, usbdev, usb_rcvintpipe(usbdev, 2),
                 catc->irq_buf, 2, catc_irq_done, catc, 1);
 
 	if (!catc->is_f5u011) {
+		u32 *buf;
+		int i;
+
 		dev_dbg(dev, "Checking memory size\n");
 
-		i = 0x12345678;
-		catc_write_mem(catc, 0x7a80, &i, 4);
-		i = 0x87654321;	
-		catc_write_mem(catc, 0xfa80, &i, 4);
-		catc_read_mem(catc, 0x7a80, &i, 4);
+		buf = kmalloc(4, GFP_KERNEL);
+		if (!buf) {
+			ret = -ENOMEM;
+			goto fail_free;
+		}
+
+		*buf = 0x12345678;
+		catc_write_mem(catc, 0x7a80, buf, 4);
+		*buf = 0x87654321;
+		catc_write_mem(catc, 0xfa80, buf, 4);
+		catc_read_mem(catc, 0x7a80, buf, 4);
 	  
-		switch (i) {
+		switch (*buf) {
 		case 0x12345678:
 			catc_set_reg(catc, TxBufCount, 8);
 			catc_set_reg(catc, RxBufCount, 32);
 			dev_dbg(dev, "64k Memory\n");
 			break;
@@ -861,10 +870,12 @@ static int catc_probe(struct usb_interface *intf, const struct usb_device_id *id
 			catc_set_reg(catc, TxBufCount, 4);
 			catc_set_reg(catc, RxBufCount, 16);
 			dev_dbg(dev, "32k Memory\n");
 			break;
 		}
+
+		kfree(buf);
 	  
 		dev_dbg(dev, "Getting MAC from SEEROM.\n");
 	  
 		catc_get_mac(catc, netdev->dev_addr);
 		

Vulnerable code: 	int i, pktsz, ret;
		i = 0x12345678;
		catc_write_mem(catc, 0x7a80, &i, 4);
		i = 0x87654321;	
		catc_write_mem(catc, 0xfa80, &i, 4);
		catc_read_mem(catc, 0x7a80, &i, 4);
		switch (i) {
Fixed code: 	int pktsz, ret;
		u32 *buf;
		int i;

		buf = kmalloc(4, GFP_KERNEL);
		if (!buf) {
			ret = -ENOMEM;
			goto fail_free;
		}

		*buf = 0x12345678;
		catc_write_mem(catc, 0x7a80, buf, 4);
		*buf = 0x87654321;
		catc_write_mem(catc, 0xfa80, buf, 4);
		catc_read_mem(catc, 0x7a80, buf, 4);
		switch (*buf) {

		kfree(buf);