[PATCH RFC 20/22] platform/x86: toshiba_acpi: let procfs copy in writes

[Christian Brauner]

Implement ->proc_write_buf() for the files in /proc/acpi/toshiba so
procfs copies in what is written before it pins the entry, and parse
what was written from that copy. Commands longer than PAGE_SIZE - 1
bytes are rejected now.

Signed-off-by: Christian Brauner (Amutable) <brauner@xxxxxxxxxx>
---
 drivers/platform/x86/toshiba_acpi.c | 36 ++++++++++++------------------------
 1 file changed, 12 insertions(+), 24 deletions(-)

diff --git a/drivers/platform/x86/toshiba_acpi.c b/drivers/platform/x86/toshiba_acpi.c
index 560e62da05a9..895e321ada03 100644
--- a/drivers/platform/x86/toshiba_acpi.c
+++ b/drivers/platform/x86/toshiba_acpi.c
@@ -1478,7 +1478,7 @@ static int set_lcd_status(struct backlight_device *bd)
 	return set_lcd_brightness(dev, bd->props.brightness);
 }
 
-static ssize_t lcd_proc_write(struct file *file, const char __user *buf,
+static ssize_t lcd_proc_write(struct file *file, char *buf,
 			      size_t count, loff_t *pos)
 {
 	struct toshiba_acpi_dev *dev = pde_data(file_inode(file));
@@ -1488,8 +1488,7 @@ static ssize_t lcd_proc_write(struct file *file, const char __user *buf,
 	int value;
 
 	len = min(count, sizeof(cmd) - 1);
-	if (copy_from_user(cmd, buf, len))
-		return -EFAULT;
+	memcpy(cmd, buf, len);
 	cmd[len] = '\0';
 
 	levels = dev->backlight_dev->props.max_brightness + 1;
@@ -1505,7 +1504,7 @@ static ssize_t lcd_proc_write(struct file *file, const char __user *buf,
 
 static const struct proc_ops lcd_proc_ops = {
 	.proc_show	= lcd_proc_show,
-	.proc_write	= lcd_proc_write,
+	.proc_write_buf	= lcd_proc_write,
 };
 
 /* Video-Out */
@@ -1541,24 +1540,17 @@ static int video_proc_show(struct seq_file *m, void *v)
 	return 0;
 }
 
-static ssize_t video_proc_write(struct file *file, const char __user *buf,
+static ssize_t video_proc_write(struct file *file, char *buf,
 				size_t count, loff_t *pos)
 {
 	struct toshiba_acpi_dev *dev = pde_data(file_inode(file));
-	char *buffer;
-	char *cmd;
+	char *buffer = buf;
 	int lcd_out = -1, crt_out = -1, tv_out = -1;
 	int remain = count;
 	int value;
 	int ret;
 	u32 video_out;
 
-	cmd = memdup_user_nul(buf, count);
-	if (IS_ERR(cmd))
-		return PTR_ERR(cmd);
-
-	buffer = cmd;
-
 	/*
 	 * Scan expression.  Multiple expressions may be delimited with ;
 	 * NOTE: To keep scanning simple, invalid fields are ignored.
@@ -1577,8 +1569,6 @@ static ssize_t video_proc_write(struct file *file, const char __user *buf,
 		} while (remain && *(buffer - 1) != ';');
 	}
 
-	kfree(cmd);
-
 	ret = get_video_status(dev, &video_out);
 	if (!ret) {
 		unsigned int new_video_out = video_out;
@@ -1602,7 +1592,7 @@ static ssize_t video_proc_write(struct file *file, const char __user *buf,
 
 static const struct proc_ops video_proc_ops = {
 	.proc_show	= video_proc_show,
-	.proc_write	= video_proc_write,
+	.proc_write_buf	= video_proc_write,
 };
 
 /* Fan status */
@@ -1644,7 +1634,7 @@ static int fan_proc_show(struct seq_file *m, void *v)
 	return 0;
 }
 
-static ssize_t fan_proc_write(struct file *file, const char __user *buf,
+static ssize_t fan_proc_write(struct file *file, char *buf,
 			      size_t count, loff_t *pos)
 {
 	struct toshiba_acpi_dev *dev = pde_data(file_inode(file));
@@ -1653,8 +1643,7 @@ static ssize_t fan_proc_write(struct file *file, const char __user *buf,
 	int value;
 
 	len = min(count, sizeof(cmd) - 1);
-	if (copy_from_user(cmd, buf, len))
-		return -EFAULT;
+	memcpy(cmd, buf, len);
 	cmd[len] = '\0';
 
 	if (sscanf(cmd, " force_on : %i", &value) != 1 ||
@@ -1671,7 +1660,7 @@ static ssize_t fan_proc_write(struct file *file, const char __user *buf,
 
 static const struct proc_ops fan_proc_ops = {
 	.proc_show	= fan_proc_show,
-	.proc_write	= fan_proc_write,
+	.proc_write_buf	= fan_proc_write,
 };
 
 /* Fan RPM */
@@ -1707,7 +1696,7 @@ static int keys_proc_show(struct seq_file *m, void *v)
 	return 0;
 }
 
-static ssize_t keys_proc_write(struct file *file, const char __user *buf,
+static ssize_t keys_proc_write(struct file *file, char *buf,
 			       size_t count, loff_t *pos)
 {
 	struct toshiba_acpi_dev *dev = pde_data(file_inode(file));
@@ -1716,8 +1705,7 @@ static ssize_t keys_proc_write(struct file *file, const char __user *buf,
 	int value;
 
 	len = min(count, sizeof(cmd) - 1);
-	if (copy_from_user(cmd, buf, len))
-		return -EFAULT;
+	memcpy(cmd, buf, len);
 	cmd[len] = '\0';
 
 	if (sscanf(cmd, " hotkey_ready : %i", &value) == 1 && value == 0)
@@ -1730,7 +1718,7 @@ static ssize_t keys_proc_write(struct file *file, const char __user *buf,
 
 static const struct proc_ops keys_proc_ops = {
 	.proc_show	= keys_proc_show,
-	.proc_write	= keys_proc_write,
+	.proc_write_buf	= keys_proc_write,
 };
 
 static int __maybe_unused version_proc_show(struct seq_file *m, void *v)

-- 
2.53.0