iommu/debug: Add mutex to make attach/detach thread safe

This mutex lock will help to synchronise the usage of iommu domain
structure which is getting used by multiple threads to perform
iommu attach and iommu detach in case of any error.

Without this change we are seeing page poisoning - write after free
when running stress tests using iommu-debug test cases.

Change-Id: I1033808a510786577c41201c2a6a330e5465d4d1
Acked-by: Ankur Saxena <c_ankusa@qti.qualcomm.com>
Signed-off-by: Vivek Gautam <vivek.gautam@codeaurora.org>

diff --git a/drivers/iommu/iommu-debug.c b/drivers/iommu/iommu-debug.c
index c21846c..b167cd3 100644 (file)
--- a/drivers/iommu/iommu-debug.c
+++ b/drivers/iommu/iommu-debug.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015-2017, The Linux Foundation. All rights reserved.
+ * Copyright (c) 2015-2018, 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
@@ -168,6 +168,7 @@ struct iommu_debug_device {
        size_t len;
        struct list_head list;
        struct mutex clk_lock;
+       struct mutex dev_lock;
        unsigned int clk_count;
 };
 
@@ -1239,6 +1240,7 @@ static ssize_t __iommu_debug_dma_attach_write(struct file *file,
        ssize_t retval = -EINVAL;
        int val;
 
+       mutex_lock(&ddev->dev_lock);
        if (kstrtoint_from_user(ubuf, count, 0, &val)) {
                pr_err("Invalid format. Expected a hex or decimal integer");
                retval = -EFAULT;
@@ -1282,12 +1284,14 @@ static ssize_t __iommu_debug_dma_attach_write(struct file *file,
                arm_iommu_release_mapping(dev->archdata.mapping);
                pr_err("Detached\n");
        }
+       mutex_unlock(&ddev->dev_lock);
        retval = count;
        return retval;
 
 out_release_mapping:
        arm_iommu_release_mapping(dma_mapping);
 out:
+       mutex_unlock(&ddev->dev_lock);
        return retval;
 }
 
@@ -1300,6 +1304,7 @@ static ssize_t __iommu_debug_attach_write(struct file *file,
        ssize_t retval;
        int val;
 
+       mutex_lock(&ddev->dev_lock);
        if (kstrtoint_from_user(ubuf, count, 0, &val)) {
                pr_err("Invalid format. Expected a hex or decimal integer");
                retval = -EFAULT;
@@ -1336,6 +1341,7 @@ static ssize_t __iommu_debug_attach_write(struct file *file,
 
        retval = count;
 out:
+       mutex_unlock(&ddev->dev_lock);
        return retval;
 }
 
@@ -2112,6 +2118,7 @@ static int snarf_iommu_devices(struct device *dev, const char *name)
        if (!ddev)
                return -ENODEV;
        mutex_init(&ddev->clk_lock);
+       mutex_init(&ddev->dev_lock);
        ddev->dev = dev;
        dir = debugfs_create_dir(name, debugfs_tests_dir);
        if (!dir) {