Merge "leds: qpnp-flash: Fix possible race condition in debugfs"

drivers/leds/leds-qpnp-flash.c

@@ -226,6 +226,7 @@ struct flash_led_platform_data {
 };
 
 struct qpnp_flash_led_buffer {
+	struct mutex debugfs_lock; /* Prevent thread concurrency */
 	size_t rpos;
 	size_t wpos;
 	size_t len;
@@ -282,6 +283,7 @@ static int flash_led_dbgfs_file_open(struct qpnp_flash_led *led,
 	log->rpos = 0;
 	log->wpos = 0;
 	log->len = logbufsize - sizeof(*log);
+	mutex_init(&log->debugfs_lock);
 	led->log = log;
 
 	led->buffer_cnt = 1;
@@ -303,20 +305,26 @@ static int flash_led_dfs_close(struct inode *inode, struct file *file)
 
 	if (led && led->log) {
 		file->private_data = NULL;
+		mutex_destroy(&led->log->debugfs_lock);
 		kfree(led->log);
 	}
 
 	return 0;
 }
 
+#define MIN_BUFFER_WRITE_LEN		20
 static int print_to_log(struct qpnp_flash_led_buffer *log,
 					const char *fmt, ...)
 {
 	va_list args;
 	int cnt;
-	char *log_buf = &log->data[log->wpos];
+	char *log_buf;
 	size_t size = log->len - log->wpos;
 
+	if (size < MIN_BUFFER_WRITE_LEN)
+		return 0;	/* not enough buffer left */
+
+	log_buf = &log->data[log->wpos];
 	va_start(args, fmt);
 	cnt = vscnprintf(log_buf, size, fmt, args);
 	va_end(args);
@@ -330,29 +338,31 @@ static ssize_t flash_led_dfs_latched_reg_read(struct file *fp, char __user *buf,
 	struct qpnp_flash_led *led = fp->private_data;
 	struct qpnp_flash_led_buffer *log = led->log;
 	uint val;
-	int rc;
+	int rc = 0;
 	size_t len;
 	size_t ret;
 
-	if (log->rpos >= log->wpos && led->buffer_cnt == 0)
-		return 0;
+	mutex_lock(&log->debugfs_lock);
+	if ((log->rpos >= log->wpos && led->buffer_cnt == 0) ||
+			((log->len - log->wpos) < MIN_BUFFER_WRITE_LEN))
+		goto unlock_mutex;
 
 	rc = regmap_read(led->regmap, INT_LATCHED_STS(led->base), &val);
 	if (rc) {
 		dev_err(&led->pdev->dev,
 				"Unable to read from address %x, rc(%d)\n",
 				INT_LATCHED_STS(led->base), rc);
-		return -EINVAL;
+		goto unlock_mutex;
 	}
 	led->buffer_cnt--;
 
 	rc = print_to_log(log, "0x%05X ", INT_LATCHED_STS(led->base));
 	if (rc == 0)
-		return rc;
+		goto unlock_mutex;
 
 	rc = print_to_log(log, "0x%02X ", val);
 	if (rc == 0)
-		return rc;
+		goto unlock_mutex;
 
 	if (log->wpos > 0 && log->data[log->wpos - 1] == ' ')
 		log->data[log->wpos - 1] = '\n';
@@ -362,36 +372,43 @@ static ssize_t flash_led_dfs_latched_reg_read(struct file *fp, char __user *buf,
 	ret = copy_to_user(buf, &log->data[log->rpos], len);
 	if (ret) {
 		pr_err("error copy register value to user\n");
-		return -EFAULT;
+		rc = -EFAULT;
+		goto unlock_mutex;
 	}
 
 	len -= ret;
 	*ppos += len;
 	log->rpos += len;
 
-	return len;
+	rc = len;
+
+unlock_mutex:
+	mutex_unlock(&log->debugfs_lock);
+	return rc;
 }
 
 static ssize_t flash_led_dfs_fault_reg_read(struct file *fp, char __user *buf,
 					size_t count, loff_t *ppos) {
 	struct qpnp_flash_led *led = fp->private_data;
 	struct qpnp_flash_led_buffer *log = led->log;
-	int rc;
+	int rc = 0;
 	size_t len;
 	size_t ret;
 
-	if (log->rpos >= log->wpos && led->buffer_cnt == 0)
-		return 0;
+	mutex_lock(&log->debugfs_lock);
+	if ((log->rpos >= log->wpos && led->buffer_cnt == 0) ||
+			((log->len - log->wpos) < MIN_BUFFER_WRITE_LEN))
+		goto unlock_mutex;
 
 	led->buffer_cnt--;
 
 	rc = print_to_log(log, "0x%05X ", FLASH_LED_FAULT_STATUS(led->base));
 	if (rc == 0)
-		return rc;
+		goto unlock_mutex;
 
 	rc = print_to_log(log, "0x%02X ", led->fault_reg);
 	if (rc == 0)
-		return rc;
+		goto unlock_mutex;
 
 	if (log->wpos > 0 && log->data[log->wpos - 1] == ' ')
 		log->data[log->wpos - 1] = '\n';
@@ -401,14 +418,19 @@ static ssize_t flash_led_dfs_fault_reg_read(struct file *fp, char __user *buf,
 	ret = copy_to_user(buf, &log->data[log->rpos], len);
 	if (ret) {
 		pr_err("error copy register value to user\n");
-		return -EFAULT;
+		rc = -EFAULT;
+		goto unlock_mutex;
 	}
 
 	len -= ret;
 	*ppos += len;
 	log->rpos += len;
 
-	return len;
+	rc = len;
+
+unlock_mutex:
+	mutex_unlock(&log->debugfs_lock);
+	return rc;
 }
 
 static ssize_t flash_led_dfs_fault_reg_enable(struct file *file,
@@ -421,10 +443,14 @@ static ssize_t flash_led_dfs_fault_reg_enable(struct file *file,
 	size_t ret = 0;
 
 	struct qpnp_flash_led *led = file->private_data;
-	char *kbuf = kmalloc(count + 1, GFP_KERNEL);
+	char *kbuf;
 
-	if (!kbuf)
-		return -ENOMEM;
+	mutex_lock(&led->log->debugfs_lock);
+	kbuf = kmalloc(count + 1, GFP_KERNEL);
+	if (!kbuf) {
+		ret = -ENOMEM;
+		goto unlock_mutex;
+	}
 
 	ret = copy_from_user(kbuf, buf, count);
 	if (!ret) {
@@ -453,6 +479,8 @@ static ssize_t flash_led_dfs_fault_reg_enable(struct file *file,
 
 free_buf:
 	kfree(kbuf);
+unlock_mutex:
+	mutex_unlock(&led->log->debugfs_lock);
 	return ret;
 }
 
@@ -465,10 +493,14 @@ static ssize_t flash_led_dfs_dbg_enable(struct file *file,
 	int data;
 	size_t ret = 0;
 	struct qpnp_flash_led *led = file->private_data;
-	char *kbuf = kmalloc(count + 1, GFP_KERNEL);
+	char *kbuf;
 
-	if (!kbuf)
-		return -ENOMEM;
+	mutex_lock(&led->log->debugfs_lock);
+	kbuf = kmalloc(count + 1, GFP_KERNEL);
+	if (!kbuf) {
+		ret = -ENOMEM;
+		goto unlock_mutex;
+	}
 
 	ret = copy_from_user(kbuf, buf, count);
 	if (ret == count) {
@@ -496,6 +528,8 @@ static ssize_t flash_led_dfs_dbg_enable(struct file *file,
 
 free_buf:
 	kfree(kbuf);
+unlock_mutex:
+	mutex_unlock(&led->log->debugfs_lock);
 	return ret;
 }