USB: serial: fix DMA buffers on stack for io_edgeport.c

The original code was passing a stack variable as a dma buffer, so I
made it an allocated variable.  Instead of adding a bunch of kfree()
calls, I changed all the error return paths to gotos.

Also I noticed that the error checking wasn't correct because
usb_get_descriptor() can return negative values.

While I was at it, I made an unrelated white space change by moving
the unicode_to_ascii() on to one line.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Cc: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 18 insertions, 17 deletions

diff --git a/drivers/usb/serial/io_edgeport.c b/drivers/usb/serial/io_edgeport.c
index b97960ac92f2..09456002bac0 100644
--- a/drivers/usb/serial/io_edgeport.c
+++ b/drivers/usb/serial/io_edgeport.c
@@ -372,31 +372,32 @@ static void update_edgeport_E2PROM(struct edgeport_serial *edge_serial)
  ************************************************************************/
 static int get_string(struct usb_device *dev, int Id, char *string, int buflen)
 {
-        struct usb_string_descriptor StringDesc;
-        struct usb_string_descriptor *pStringDesc;
+        struct usb_string_descriptor *StringDesc = NULL;
+        struct usb_string_descriptor *pStringDesc = NULL;
+        int ret = 0;
 
         dbg("%s - USB String ID = %d", __func__, Id);
 
-        if (!usb_get_descriptor(dev, USB_DT_STRING, Id,
-                                        &StringDesc, sizeof(StringDesc)))
-                return 0;
+        StringDesc = kmalloc(sizeof(*StringDesc), GFP_KERNEL);
+        if (!StringDesc)
+                goto free;
+        if (usb_get_descriptor(dev, USB_DT_STRING, Id, StringDesc, sizeof(*StringDesc)) <= 0)
+                goto free;
 
-        pStringDesc = kmalloc(StringDesc.bLength, GFP_KERNEL);
+        pStringDesc = kmalloc(StringDesc->bLength, GFP_KERNEL);
         if (!pStringDesc)
-                return 0;
+                goto free;
 
-        if (!usb_get_descriptor(dev, USB_DT_STRING, Id,
-                                        pStringDesc, StringDesc.bLength)) {
-                kfree(pStringDesc);
-                return 0;
-        }
-
-        unicode_to_ascii(string, buflen,
-                                pStringDesc->wData, pStringDesc->bLength/2);
+        if (usb_get_descriptor(dev, USB_DT_STRING, Id, pStringDesc, StringDesc->bLength) <= 0)
+                goto free;
 
-        kfree(pStringDesc);
+        unicode_to_ascii(string, buflen, pStringDesc->wData, pStringDesc->bLength/2);
+        ret = strlen(string);
         dbg("%s - USB String %s", __func__, string);
-        return strlen(string);
+free:
+        kfree(StringDesc);
+        kfree(pStringDesc);
+        return ret;
 }