Vulnerability: 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.
Vulnerability ID: CVE-2017-8070
CWE: CWE-119
Severity score: 10
Project: https://github.com/torvalds/linux
Published: 2017-04-23
File: drivers/net/usb/catc.c
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>
Commit author: Ben Hutchings

Vulnerable version (before fix):
 static int catc_probe(struct usb_interface *intf, const struct usb_device_id *id 	struct net_device *netdev; 	struct catc *catc; 	u8 broadcast[ETH_ALEN]; 	int i, pktsz, ret;  	if (usb_set_interface(usbdev, 			intf->altsetting->desc.bInterfaceNumber, 1)) { static int catc_probe(struct usb_interface *intf, const struct usb_device_id *id                 catc->irq_buf, 2, catc_irq_done, catc, 1);  	if (!catc->is_f5u011) { 		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); 	   		switch (i) { 		case 0x12345678: 			catc_set_reg(catc, TxBufCount, 8); 			catc_set_reg(catc, RxBufCount, 32); static int catc_probe(struct usb_interface *intf, const struct usb_device_id *id 			dev_dbg(dev, "32k Memory\n"); 			break; 		} 	   		dev_dbg(dev, "Getting MAC from SEEROM.\n"); 	  

Fixed version (after fix):
 static int catc_probe(struct usb_interface *intf, const struct usb_device_id *id 	struct net_device *netdev; 	struct catc *catc; 	u8 broadcast[ETH_ALEN]; 	int pktsz, ret;  	if (usb_set_interface(usbdev, 			intf->altsetting->desc.bInterfaceNumber, 1)) { static int catc_probe(struct usb_interface *intf, const struct usb_device_id *id                 catc->irq_buf, 2, catc_irq_done, catc, 1);  	if (!catc->is_f5u011) { 		u32 *buf; 		int i;  		dev_dbg(dev, "Checking memory size\n");  		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) { 		case 0x12345678: 			catc_set_reg(catc, TxBufCount, 8); 			catc_set_reg(catc, RxBufCount, 32); static int catc_probe(struct usb_interface *intf, const struct usb_device_id *id 			dev_dbg(dev, "32k Memory\n"); 			break; 		}  		kfree(buf); 	   		dev_dbg(dev, "Getting MAC from SEEROM.\n"); 	  

Patch:
patch: @@ -776,7 +776,7 @@ static int catc_probe(struct usb_interface *intf, const struct usb_device_id *id
 	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)) {
@@ -840,15 +840,24 @@ static int catc_probe(struct usb_interface *intf, const struct usb_device_id *id
                 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);
@@ -863,6 +872,8 @@ static int catc_probe(struct usb_interface *intf, const struct usb_device_id *id
 			dev_dbg(dev, "32k Memory\n");
 			break;
 		}
+
+		kfree(buf);
 	  
 		dev_dbg(dev, "Getting MAC from SEEROM.\n");
path: drivers/net/usb/catc.c