[PATCH] Fix check warnings in PPP code

This patch removes the warnings that the check program came up with in
the PPP code: ppp_async.c, ppp_deflate.c and ppp_generic.c.  This
involved adding __user and converting K&R-style function definitions
to ANSI-style.  I also took the time to add some extra comments to
ppp_deflate.c explaining in more detail what each function does and
what its arguments are.

drivers/net/ppp_async.c

@@ -427,12 +427,12 @@ ppp_async_ioctl(struct ppp_channel *chan, unsigned int cmd, unsigned long arg)
 		break;
 
 	case PPPIOCGXASYNCMAP:
-		if (copy_to_user((void *) arg, ap->xaccm, sizeof(ap->xaccm)))
+		if (copy_to_user((void __user *) arg, ap->xaccm, sizeof(ap->xaccm)))
 			break;
 		err = 0;
 		break;
 	case PPPIOCSXASYNCMAP:
-		if (copy_from_user(accm, (void *) arg, sizeof(accm)))
+		if (copy_from_user(accm, (void __user *) arg, sizeof(accm)))
 			break;
 		accm[2] &= ~0x40000000U;	/* can't escape 0x5e */
 		accm[3] |= 0x60000000U;		/* must escape 0x7d, 0x7e */

drivers/net/ppp_generic.c

@@ -387,7 +387,7 @@ static int ppp_release(struct inode *inode, struct file *file)
 	return 0;
 }
 
-static ssize_t ppp_read(struct file *file, char *buf,
+static ssize_t ppp_read(struct file *file, char __user *buf,
 			size_t count, loff_t *ppos)
 {
 	struct ppp_file *pf = file->private_data;
@@ -436,7 +436,7 @@ static ssize_t ppp_read(struct file *file, char *buf,
 	return ret;
 }
 
-static ssize_t ppp_write(struct file *file, const char *buf,
+static ssize_t ppp_write(struct file *file, const char __user *buf,
 			 size_t count, loff_t *ppos)
 {
 	struct ppp_file *pf = file->private_data;
@@ -617,7 +617,7 @@ static int ppp_ioctl(struct inode *inode, struct file *file,
 	case PPPIOCGIDLE:
 		idle.xmit_idle = (jiffies - ppp->last_xmit) / HZ;
 		idle.recv_idle = (jiffies - ppp->last_recv) / HZ;
-		if (copy_to_user((void *) arg, &idle, sizeof(idle)))
+		if (copy_to_user((void __user *) arg, &idle, sizeof(idle)))
 			break;
 		err = 0;
 		break;
@@ -646,7 +646,7 @@ static int ppp_ioctl(struct inode *inode, struct file *file,
 
 	case PPPIOCGNPMODE:
 	case PPPIOCSNPMODE:
-		if (copy_from_user(&npi, (void *) arg, sizeof(npi)))
+		if (copy_from_user(&npi, (void __user *) arg, sizeof(npi)))
 			break;
 		err = proto_to_npindex(npi.protocol);
 		if (err < 0)
@@ -655,7 +655,7 @@ static int ppp_ioctl(struct inode *inode, struct file *file,
 		if (cmd == PPPIOCGNPMODE) {
 			err = -EFAULT;
 			npi.mode = ppp->npmode[i];
-			if (copy_to_user((void *) arg, &npi, sizeof(npi)))
+			if (copy_to_user((void __user *) arg, &npi, sizeof(npi)))
 				break;
 		} else {
 			ppp->npmode[i] = npi.mode;
@@ -673,16 +673,15 @@ static int ppp_ioctl(struct inode *inode, struct file *file,
 		struct sock_filter *code = NULL;
 		int len;
 
-		if (copy_from_user(&uprog, (void *) arg, sizeof(uprog)))
+		if (copy_from_user(&uprog, (void __user *) arg, sizeof(uprog)))
 			break;
-		if (uprog.len > 0 && uprog.len < 65536) {
 		err = -ENOMEM;
 		len = uprog.len * sizeof(struct sock_filter);
 		code = kmalloc(len, GFP_KERNEL);
 		if (code == 0)
 			break;
 		err = -EFAULT;
-			if (copy_from_user(code, uprog.filter, len)) {
+		if (copy_from_user(code, (void __user *) uprog.filter, len)) {
 			kfree(code);
 			break;
 		}
@@ -691,7 +690,6 @@ static int ppp_ioctl(struct inode *inode, struct file *file,
 			kfree(code);
 			break;
 		}
-		}
 		filtp = (cmd == PPPIOCSPASS)? &ppp->pass_filter: &ppp->active_filter;
 		ppp_lock(ppp);
 		if (filtp->filter)
@@ -879,7 +877,7 @@ ppp_net_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
 {
 	struct ppp *ppp = dev->priv;
 	int err = -EFAULT;
-	void *addr = (void *) ifr->ifr_ifru.ifru_data;
+	void __user *addr = (void __user *) ifr->ifr_ifru.ifru_data;
 	struct ppp_stats stats;
 	struct ppp_comp_stats cstats;
 	char *vers;
@@ -1952,9 +1950,9 @@ ppp_set_compress(struct ppp *ppp, unsigned long arg)
 	unsigned char ccp_option[CCP_MAX_OPTION_LENGTH];
 
 	err = -EFAULT;
-	if (copy_from_user(&data, (void *) arg, sizeof(data))
+	if (copy_from_user(&data, (void __user *) arg, sizeof(data))
 	    || (data.length <= CCP_MAX_OPTION_LENGTH
-		&& copy_from_user(ccp_option, data.ptr, data.length)))
+		&& copy_from_user(ccp_option, (void __user *) data.ptr, data.length)))
 		goto out;
 	err = -EINVAL;
 	if (data.length > CCP_MAX_OPTION_LENGTH