media: v4l2-core: split out data copy from video_usercopy

The copy-in/out portions of video_usercopy() are about to
get more complex, so turn then into separate functions as
a cleanup first.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/media/v4l2-core/v4l2-ioctl.c

@@ -3023,8 +3023,69 @@ static int check_array_args(unsigned int cmd, void *parg, size_t *array_size,
 	return ret;
 }
 
+static unsigned int video_translate_cmd(unsigned int cmd)
+{
+	return cmd;
+}
+
+static int video_get_user(void __user *arg, void *parg, unsigned int cmd,
+			  bool *always_copy)
+{
+	unsigned int n = _IOC_SIZE(cmd);
+
+	if (!(_IOC_DIR(cmd) & _IOC_WRITE)) {
+		/* read-only ioctl */
+		memset(parg, 0, n);
+		return 0;
+	}
+
+	switch (cmd) {
+	default:
+		/*
+		 * In some cases, only a few fields are used as input,
+		 * i.e. when the app sets "index" and then the driver
+		 * fills in the rest of the structure for the thing
+		 * with that index.  We only need to copy up the first
+		 * non-input field.
+		 */
+		if (v4l2_is_known_ioctl(cmd)) {
+			u32 flags = v4l2_ioctls[_IOC_NR(cmd)].flags;
+
+			if (flags & INFO_FL_CLEAR_MASK)
+				n = (flags & INFO_FL_CLEAR_MASK) >> 16;
+			*always_copy = flags & INFO_FL_ALWAYS_COPY;
+		}
+
+		if (copy_from_user(parg, (void __user *)arg, n))
+			return -EFAULT;
+
+		/* zero out anything we don't copy from userspace */
+		if (n < _IOC_SIZE(cmd))
+			memset((u8 *)parg + n, 0, _IOC_SIZE(cmd) - n);
+		break;
+	}
+
+	return 0;
+}
+
+static int video_put_user(void __user *arg, void *parg, unsigned int cmd)
+{
+	if (!(_IOC_DIR(cmd) & _IOC_READ))
+		return 0;
+
+	switch (cmd) {
+	default:
+		/*  Copy results into user buffer  */
+		if (copy_to_user(arg, parg, _IOC_SIZE(cmd)))
+			return -EFAULT;
+		break;
+	}
+
+	return 0;
+}
+
 long
-video_usercopy(struct file *file, unsigned int cmd, unsigned long arg,
+video_usercopy(struct file *file, unsigned int orig_cmd, unsigned long arg,
 	       v4l2_kioctl func)
 {
 	char	sbuf[128];
@@ -3036,6 +3097,7 @@ video_usercopy(struct file *file, unsigned int cmd, unsigned long arg,
 	size_t  array_size = 0;
 	void __user *user_ptr = NULL;
 	void	**kernel_ptr = NULL;
+	unsigned int cmd = video_translate_cmd(orig_cmd);
 	const size_t ioc_size = _IOC_SIZE(cmd);
 
 	/*  Copy arguments into temp kernel buffer  */
@@ -3050,37 +3112,12 @@ video_usercopy(struct file *file, unsigned int cmd, unsigned long arg,
 			parg = mbuf;
 		}
 
-		err = -EFAULT;
-		if (_IOC_DIR(cmd) & _IOC_WRITE) {
-			unsigned int n = ioc_size;
-
-			/*
-			 * In some cases, only a few fields are used as input,
-			 * i.e. when the app sets "index" and then the driver
-			 * fills in the rest of the structure for the thing
-			 * with that index.  We only need to copy up the first
-			 * non-input field.
-			 */
-			if (v4l2_is_known_ioctl(cmd)) {
-				u32 flags = v4l2_ioctls[_IOC_NR(cmd)].flags;
-
-				if (flags & INFO_FL_CLEAR_MASK)
-					n = (flags & INFO_FL_CLEAR_MASK) >> 16;
-				always_copy = flags & INFO_FL_ALWAYS_COPY;
-			}
-
-			if (copy_from_user(parg, (void __user *)arg, n))
-				goto out;
-
-			/* zero out anything we don't copy from userspace */
-			if (n < ioc_size)
-				memset((u8 *)parg + n, 0, ioc_size - n);
-		} else {
-			/* read-only ioctl */
-			memset(parg, 0, ioc_size);
-		}
 	}
 
+	err = video_get_user((void __user *)arg, parg, orig_cmd, &always_copy);
+	if (err)
+		goto out;
+
 	err = check_array_args(cmd, parg, &array_size, &user_ptr, &kernel_ptr);
 	if (err < 0)
 		goto out;
@@ -3131,15 +3168,8 @@ video_usercopy(struct file *file, unsigned int cmd, unsigned long arg,
 		goto out;
 
 out_array_args:
-	/*  Copy results into user buffer  */
-	switch (_IOC_DIR(cmd)) {
-	case _IOC_READ:
-	case (_IOC_WRITE | _IOC_READ):
-		if (copy_to_user((void __user *)arg, parg, ioc_size))
-			err = -EFAULT;
-		break;
-	}
-
+	if (video_put_user((void __user *)arg, parg, orig_cmd))
+		err = -EFAULT;
 out:
 	kvfree(mbuf);
 	return err;