input: synaptics: put offset checks under mutex.

Place file offset validity checks under mutex.

BUG: 33555878
BUG: 33002026

Change-Id: I1945cfc8af7d1a310ae0d7bbb85002d4c448f30b
Signed-off-by: Andrew Chant <[email protected]>
Git-repo: https://android.googlesource.com/kernel/msm
Git-commit: e1fb160
Resolved minor merge conflict
Signed-off-by: Srinivasa Rao Kuppala <[email protected]>

Author: Andrew Chant

drivers/input/touchscreen/synaptics_rmi_dev.c

@@ -299,18 +299,26 @@ static ssize_t rmidev_read(struct file *filp, char __user *buf,
 		return -EBADF;
 	}
 
-	if (count == 0)
-		return 0;
+	mutex_lock(&(dev_data->file_mutex));
 
 	if (count > (REG_ADDR_LIMIT - *f_pos))
 		count = REG_ADDR_LIMIT - *f_pos;
 
-	tmpbuf = kzalloc(count + 1, GFP_KERNEL);
-	if (!tmpbuf)
-		return -ENOMEM;
+	if (count == 0) {
+		retval = 0;
+		goto unlock;
+	}
 
-	mutex_lock(&(dev_data->file_mutex));
+	if (*f_pos > REG_ADDR_LIMIT) {
+		retval = -EFAULT;
+		goto unlock;
+	}
 
+	tmpbuf = kzalloc(count + 1, GFP_KERNEL);
+	if (!tmpbuf) {
+		retval = -ENOMEM;
+		goto unlock;
+	}
 	retval = rmidev->fn_ptr->read(rmidev->rmi4_data,
 			*f_pos,
 			tmpbuf,
@@ -324,8 +332,9 @@ static ssize_t rmidev_read(struct file *filp, char __user *buf,
 		*f_pos += retval;
 
 clean_up:
-	mutex_unlock(&(dev_data->file_mutex));
 	kfree(tmpbuf);
+unlock:
+	mutex_unlock(&(dev_data->file_mutex));
 	return retval;
 }
 
@@ -349,32 +358,43 @@ static ssize_t rmidev_write(struct file *filp, const char __user *buf,
 		return -EBADF;
 	}
 
-	if (count == 0)
-		return 0;
+	mutex_lock(&(dev_data->file_mutex));
+
+	if (*f_pos > REG_ADDR_LIMIT) {
+		retval = -EFAULT;
+		goto unlock;
+	}
 
 	if (count > (REG_ADDR_LIMIT - *f_pos))
 		count = REG_ADDR_LIMIT - *f_pos;
 
+	if (count == 0) {
+		retval = 0;
+		goto unlock;
+	}
+
 	tmpbuf = kzalloc(count + 1, GFP_KERNEL);
-	if (!tmpbuf)
-		return -ENOMEM;
+	if (!tmpbuf) {
+		retval = -ENOMEM;
+		goto unlock;
+	}
 
 	if (copy_from_user(tmpbuf, buf, count)) {
-		kfree(tmpbuf);
-		return -EFAULT;
+		retval = -EFAULT;
+		goto clean_up;
 	}
 
-	mutex_lock(&(dev_data->file_mutex));
-
 	retval = rmidev->fn_ptr->write(rmidev->rmi4_data,
 			*f_pos,
 			tmpbuf,
 			count);
 	if (retval >= 0)
 		*f_pos += retval;
 
-	mutex_unlock(&(dev_data->file_mutex));
+clean_up:
 	kfree(tmpbuf);
+unlock:
+	mutex_unlock(&(dev_data->file_mutex));
 	return retval;
 }