[PATCH] ISDN: correctly handle isdn_writebuf_stub() errors

isdn_writebuf_stub() forgets to detect memory allocation and uaccess errors.
And when that's fixed, if a error happens the caller will just keep on
looping.

So change the caller to detect the error, and to return it.

Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com>
Cc: Karsten Keil <kkeil@suse.de>
Signed-off-by: Tilman Schmidt <tilman@imap.cc>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/isdn/i4l/isdn_common.c

@@ -1177,9 +1177,8 @@ isdn_write(struct file *file, const char __user *buf, size_t count, loff_t * off
 			goto out;
 		}
 		chidx = isdn_minor2chan(minor);
-		while (isdn_writebuf_stub(drvidx, chidx, buf, count) != count)
+		while ((retval = isdn_writebuf_stub(drvidx, chidx, buf, count)) == 0)
 			interruptible_sleep_on(&dev->drv[drvidx]->snd_waitq[chidx]);
-		retval = count;
 		goto out;
 	}
 	if (minor <= ISDN_MINOR_CTRLMAX) {
@@ -1951,9 +1950,10 @@ isdn_writebuf_stub(int drvidx, int chan, const u_char __user * buf, int len)
 	struct sk_buff *skb = alloc_skb(hl + len, GFP_ATOMIC);
 
 	if (!skb)
-		return 0;
+		return -ENOMEM;
 	skb_reserve(skb, hl);
-	copy_from_user(skb_put(skb, len), buf, len);
+	if (copy_from_user(skb_put(skb, len), buf, len))
+		return -EFAULT;
 	ret = dev->drv[drvidx]->interface->writebuf_skb(drvidx, chan, 1, skb);
 	if (ret <= 0)
 		dev_kfree_skb(skb);