[PATCH 4.19 087/243] media: coda: fix memory corruption in case more than 32 instances are opened

Greg Kroah-Hartman
2019-12-11T15:53:11Z

From: Philipp Zabel <p.zabel@pengutronix.de>

[ Upstream commit 649cfc2bdfeeb98ff7d8fdff0af3f8fb9c8da50f ]

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@pengutronix.de>
Signed-off-by: Hans Verkuil <hansverk@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/media/platform/coda/coda-common.c | 26 +++++++++--------------
drivers/media/platform/coda/coda.h | 3 ++-
2 files changed, 12 insertions(+), 17 deletions(-)

diff --git a/drivers/media/platform/coda/coda-common.c b/drivers/media/platform/coda/coda-common.c
index 4b0220f40b425..fccc771d23a51 100644
--- a/drivers/media/platform/coda/coda-common.c
+++ b/drivers/media/platform/coda/coda-common.c
@@ -17,6 +17,7 @@
#include <linux/firmware.h>
#include <linux/gcd.h>
#include <linux/genalloc.h>
+#include <linux/idr.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/irq.h>
@@ -2101,17 +2102,6 @@ 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
*/
@@ -2120,7 +2110,8 @@ 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;
@@ -2129,12 +2120,13 @@ 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) {
@@ -2243,8 +2235,8 @@ err_clk_per:
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;
@@ -2286,7 +2278,7 @@ 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);
@@ -2747,6 +2739,7 @@ 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)
@@ -2834,6 +2827,7 @@ 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 2469ca1dc5985..8df02c32781ee 100644
--- a/drivers/media/platform/coda/coda.h
+++ b/drivers/media/platform/coda/coda.h
@@ -16,6 +16,7 @@
#define __CODA_H__

#include <linux/debugfs.h>
+#include <linux/idr.h>
#include <linux/irqreturn.h>
#include <linux/mutex.h>
#include <linux/kfifo.h>
@@ -95,7 +96,7 @@ 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;
};

--
2.20.1