usblp: Fix a double kfree

If submit fails, slab hits a BUG() because of a double kfree.
The today's lesson is, you cannot just slap USB_FREE_BUFFER on code
without adjusting the error paths.

The patch is made bigger by opportunistic refactoring.

Signed-Off-By: Pete Zaitcev <zaitcev@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 23 insertions, 12 deletions

diff --git a/drivers/usb/class/usblp.c b/drivers/usb/class/usblp.c
index 3a0f8186d4b..ad632f2d6f9 100644
--- a/drivers/usb/class/usblp.c
+++ b/drivers/usb/class/usblp.c
@@ -686,10 +686,30 @@ done:
         return retval;
 }
 
+static struct urb *usblp_new_writeurb(struct usblp *usblp, int transfer_length)
+{
+        struct urb *urb;
+        char *writebuf;
+
+        if ((writebuf = kmalloc(transfer_length, GFP_KERNEL)) == NULL)
+                return NULL;
+        if ((urb = usb_alloc_urb(0, GFP_KERNEL)) == NULL) {
+                kfree(writebuf);
+                return NULL;
+        }
+
+        usb_fill_bulk_urb(urb, usblp->dev,
+                usb_sndbulkpipe(usblp->dev,
+                 usblp->protocol[usblp->current_protocol].epwrite->bEndpointAddress),
+                writebuf, transfer_length, usblp_bulk_write, usblp);
+        urb->transfer_flags |= URB_FREE_BUFFER;
+
+        return urb;
+}
+
 static ssize_t usblp_write(struct file *file, const char __user *buffer, size_t count, loff_t *ppos)
 {
         struct usblp *usblp = file->private_data;
-        char *writebuf;
         struct urb *writeurb;
         int rv;
         int transfer_length;
@@ -710,18 +730,11 @@ static ssize_t usblp_write(struct file *file, const char __user *buffer, size_t
                         transfer_length = USBLP_BUF_SIZE;
 
                 rv = -ENOMEM;
-                if ((writebuf = kmalloc(USBLP_BUF_SIZE, GFP_KERNEL)) == NULL)
-                        goto raise_buf;
-                if ((writeurb = usb_alloc_urb(0, GFP_KERNEL)) == NULL)
+                if ((writeurb = usblp_new_writeurb(usblp, transfer_length)) == NULL)
                         goto raise_urb;
-                usb_fill_bulk_urb(writeurb, usblp->dev,
-                        usb_sndbulkpipe(usblp->dev,
-                          usblp->protocol[usblp->current_protocol].epwrite->bEndpointAddress),
-                        writebuf, transfer_length, usblp_bulk_write, usblp);
-                writeurb->transfer_flags |= URB_FREE_BUFFER;
                 usb_anchor_urb(writeurb, &usblp->urbs);
 
-                if (copy_from_user(writebuf,
+                if (copy_from_user(writeurb->transfer_buffer,
                                    buffer + writecount, transfer_length)) {
                         rv = -EFAULT;
                         goto raise_badaddr;
@@ -780,8 +793,6 @@ raise_badaddr:
         usb_unanchor_urb(writeurb);
         usb_free_urb(writeurb);
 raise_urb:
-        kfree(writebuf);
-raise_buf:
 raise_wait:
 collect_error:          /* Out of raise sequence */
         mutex_unlock(&usblp->wmut);