i2c-dev: Use memdup_user

Use memdup_user rather than duplicating its implementation.
This is a little bit restricted to reduce false positives.

The semantic patch that makes this output is available
in scripts/coccinelle/api/memdup_user.cocci.

More information about semantic patching is available at
http://coccinelle.lip6.fr/

Signed-off-by: Thomas Meyer <thomas@m3y3r.de>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

drivers/i2c/i2c-dev.c

@@ -251,15 +251,10 @@ static noinline int i2cdev_ioctl_rdrw(struct i2c_client *client,
 	if (rdwr_arg.nmsgs > I2C_RDRW_IOCTL_MAX_MSGS)
 		return -EINVAL;
 
-	rdwr_pa = kmalloc(rdwr_arg.nmsgs * sizeof(struct i2c_msg), GFP_KERNEL);
-	if (!rdwr_pa)
-		return -ENOMEM;
-
-	if (copy_from_user(rdwr_pa, rdwr_arg.msgs,
-			   rdwr_arg.nmsgs * sizeof(struct i2c_msg))) {
-		kfree(rdwr_pa);
-		return -EFAULT;
-	}
+	rdwr_pa = memdup_user(rdwr_arg.msgs,
+			      rdwr_arg.nmsgs * sizeof(struct i2c_msg));
+	if (IS_ERR(rdwr_pa))
+		return PTR_ERR(rdwr_pa);
 
 	data_ptrs = kmalloc(rdwr_arg.nmsgs * sizeof(u8 __user *), GFP_KERNEL);
 	if (data_ptrs == NULL) {