[PATCH 01/15] media: coda: fix memory corruption in case more than 32 instances are opened

[Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>]

The ffz() return value is undefined if the instance mask does not
contain any zeros. If it returned 32, the following set_bit would
corrupt the debugfs_root pointer.
Switch to IDA for context index allocation. This also removes the
artificial 32 instance limit for all except CodaDx6.

Signed-off-by: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>
---
 drivers/media/platform/coda/coda-common.c | 25 ++++++++---------------
 drivers/media/platform/coda/coda.h        |  2 +-
 2 files changed, 10 insertions(+), 17 deletions(-)

diff --git a/drivers/media/platform/coda/coda-common.c b/drivers/media/platform/coda/coda-common.c
index 2848ea5f464d..cbb59c2f3a82 100644
--- a/drivers/media/platform/coda/coda-common.c
+++ b/drivers/media/platform/coda/coda-common.c
@@ -2099,17 +2099,6 @@ int coda_decoder_queue_init(void *priv, struct vb2_queue *src_vq,
 	return coda_queue_init(priv, dst_vq);
 }
 
-static int coda_next_free_instance(struct coda_dev *dev)
-{
-	int idx = ffz(dev->instance_mask);
-
-	if ((idx < 0) ||
-	    (dev->devtype->product == CODA_DX6 && idx > CODADX6_MAX_INSTANCES))
-		return -EBUSY;
-
-	return idx;
-}
-
 /*
  * File operations
  */
@@ -2118,7 +2107,8 @@ static int coda_open(struct file *file)
 {
 	struct video_device *vdev = video_devdata(file);
 	struct coda_dev *dev = video_get_drvdata(vdev);
-	struct coda_ctx *ctx = NULL;
+	struct coda_ctx *ctx;
+	unsigned int max = ~0;
 	char *name;
 	int ret;
 	int idx;
@@ -2127,12 +2117,13 @@ static int coda_open(struct file *file)
 	if (!ctx)
 		return -ENOMEM;
 
-	idx = coda_next_free_instance(dev);
+	if (dev->devtype->product == CODA_DX6)
+		max = CODADX6_MAX_INSTANCES - 1;
+	idx = ida_alloc_max(&dev->ida, max, GFP_KERNEL);
 	if (idx < 0) {
 		ret = idx;
 		goto err_coda_max;
 	}
-	set_bit(idx, &dev->instance_mask);
 
 	name = kasprintf(GFP_KERNEL, "context%d", idx);
 	if (!name) {
@@ -2241,8 +2232,8 @@ static int coda_open(struct file *file)
 err_pm_get:
 	v4l2_fh_del(&ctx->fh);
 	v4l2_fh_exit(&ctx->fh);
-	clear_bit(ctx->idx, &dev->instance_mask);
 err_coda_name_init:
+	ida_free(&dev->ida, ctx->idx);
 err_coda_max:
 	kfree(ctx);
 	return ret;
@@ -2284,7 +2275,7 @@ static int coda_release(struct file *file)
 	pm_runtime_put_sync(&dev->plat_dev->dev);
 	v4l2_fh_del(&ctx->fh);
 	v4l2_fh_exit(&ctx->fh);
-	clear_bit(ctx->idx, &dev->instance_mask);
+	ida_free(&dev->ida, ctx->idx);
 	if (ctx->ops->release)
 		ctx->ops->release(ctx);
 	debugfs_remove_recursive(ctx->debugfs_entry);
@@ -2745,6 +2736,7 @@ static int coda_probe(struct platform_device *pdev)
 
 	mutex_init(&dev->dev_mutex);
 	mutex_init(&dev->coda_mutex);
+	ida_init(&dev->ida);
 
 	dev->debugfs_root = debugfs_create_dir("coda", NULL);
 	if (!dev->debugfs_root)
@@ -2832,6 +2824,7 @@ static int coda_remove(struct platform_device *pdev)
 	coda_free_aux_buf(dev, &dev->tempbuf);
 	coda_free_aux_buf(dev, &dev->workbuf);
 	debugfs_remove_recursive(dev->debugfs_root);
+	ida_destroy(&dev->ida);
 	return 0;
 }
 
diff --git a/drivers/media/platform/coda/coda.h b/drivers/media/platform/coda/coda.h
index 19ac0b9dc6eb..b6cd14ee91ea 100644
--- a/drivers/media/platform/coda/coda.h
+++ b/drivers/media/platform/coda/coda.h
@@ -95,7 +95,7 @@ struct coda_dev {
 	struct workqueue_struct	*workqueue;
 	struct v4l2_m2m_dev	*m2m_dev;
 	struct list_head	instances;
-	unsigned long		instance_mask;
+	struct ida		ida;
 	struct dentry		*debugfs_root;
 };
 
-- 
2.19.1