DivestOS/Patches/Linux_CVEs/CVE-2016-10295/ANY/0.patch

From f11ae3df500bc2a093ddffee6ea40da859de0fa9 Mon Sep 17 00:00:00 2001
From: ansharma <ansharma@codeaurora.org>
Date: Thu, 19 Jan 2017 20:22:14 +0530
Subject: leds: qpnp-flash: Fix possible race condition in debugfs

There is a possible race condition when debugfs files are concurrently
accessed by multiple threads. Fix this.

CRs-Fixed: 1109420, 1109326
Change-Id: I19e9107079ac8d039b12a37ae612727f824552d4
Signed-off-by: ansharma <ansharma@codeaurora.org>
---
 drivers/leds/leds-qpnp-flash.c | 80 ++++++++++++++++++++++++++++++------------
 1 file changed, 57 insertions(+), 23 deletions(-)

diff --git a/drivers/leds/leds-qpnp-flash.c b/drivers/leds/leds-qpnp-flash.c
index 43298a7..56ba8f5 100644
--- a/drivers/leds/leds-qpnp-flash.c
+++ b/drivers/leds/leds-qpnp-flash.c
@@ -1,4 +1,4 @@
-/* Copyright (c) 2014-2016, The Linux Foundation. All rights reserved.
+/* Copyright (c) 2014-2017, The Linux Foundation. All rights reserved.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 and
@@ -225,6 +225,7 @@ 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;
@@ -280,6 +281,7 @@ 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;
@@ -301,20 +303,26 @@ 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);
@@ -328,12 +336,14 @@ 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;
 	u8 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 = spmi_ext_register_readl(led->spmi_dev->ctrl,
 		led->spmi_dev->sid, INT_LATCHED_STS(led->base), &val, 1);
@@ -341,17 +351,17 @@ static ssize_t flash_led_dfs_latched_reg_read(struct file *fp, char __user *buf,
 		dev_err(&led->spmi_dev->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';
@@ -361,36 +371,43 @@ 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';
@@ -400,14 +417,19 @@ 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,
@@ -420,10 +442,14 @@ 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) {
@@ -452,6 +478,8 @@ 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;
 }
 
@@ -464,10 +492,14 @@ 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) {
@@ -495,6 +527,8 @@ 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;
 }
 
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