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Subject[PATCH 2/2] vimc: fix BUG: unable to handle kernel NULL pointer dereference
Date
If vimc module is removed while streaming is active, vimc_exit runs
into NULL pointer dereference error when streaming thread tries to
access and lock graph_mutex in the struct media_device.

media_device is embedded in struct vimc_device and when vimc is removed
vimc_device and the embedded media_device goes with it, while the active
stream and vimc_capture continue to access it.

Fix the media_device lifetime problem by changing vimc to create shared
media_device using Media Device Allocator API and vimc_capture getting
a reference to vimc module. With this change, vimc module can be removed
only when the references are gone. vimc can be removed after vimc_capture
is removed.

The following panic is fixed with this change.

kernel: [ 1844.098372] Call Trace:
kernel: [ 1844.098376] lock_acquire+0xb4/0x160
kernel: [ 1844.098379] ? media_pipeline_stop+0x23/0x40
kernel: [ 1844.098381] ? media_pipeline_stop+0x23/0x40
kernel: [ 1844.098385] __mutex_lock+0x8b/0x950
kernel: [ 1844.098386] ? media_pipeline_stop+0x23/0x40
kernel: [ 1844.098389] ? wait_for_completion+0xac/0x150
kernel: [ 1844.098391] ? wait_for_completion+0x12a/0x150
kernel: [ 1844.098395] ? wake_up_q+0x80/0x80
kernel: [ 1844.098397] mutex_lock_nested+0x1b/0x20
kernel: [ 1844.098398] ? mutex_lock_nested+0x1b/0x20
kernel: [ 1844.098400] media_pipeline_stop+0x23/0x40
kernel: [ 1844.098404] vimc_cap_stop_streaming+0x28/0x40 [vimc_capture]
kernel: [ 1844.098406] __vb2_queue_cancel+0x30/0x2a0
kernel: [ 1844.098408] vb2_core_queue_release+0x23/0x50
kernel: [ 1844.098410] vb2_queue_release+0xe/0x10
kernel: [ 1844.098412] vimc_cap_comp_unbind+0x1d/0x40 [vimc_capture]
kernel: [ 1844.098414] component_unbind.isra.8+0x27/0x40
kernel: [ 1844.098416] component_unbind_all+0xaa/0xc0
kernel: [ 1844.098418] vimc_comp_unbind+0x2d/0x60 [vimc]
kernel: [ 1844.098420] take_down_master+0x24/0x40
kernel: [ 1844.098422] component_master_del+0x5e/0x80
kernel: [ 1844.098424] vimc_remove+0x27/0x90 [vimc]
kernel: [ 1844.098426] platform_drv_remove+0x28/0x50
kernel: [ 1844.098428] device_release_driver_internal+0xec/0x1c0
kernel: [ 1844.098429] driver_detach+0x49/0x90
kernel: [ 1844.098432] bus_remove_driver+0x5c/0xd0
kernel: [ 1844.098433] driver_unregister+0x2c/0x40
kernel: [ 1844.098435] platform_driver_unregister+0x12/0x20
kernel: [ 1844.098437] vimc_exit+0x10/0x9fa [vimc]
kernel: [ 1844.098439] __x64_sys_delete_module+0x148/0x280
kernel: [ 1844.098443] do_syscall_64+0x5a/0x120
kernel: [ 1844.098446] entry_SYSCALL_64_after_hwframe+0x44/0xa9

Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
---
drivers/media/platform/vimc/vimc-capture.c | 17 +++++-
drivers/media/platform/vimc/vimc-core.c | 60 ++++++++++++----------
2 files changed, 50 insertions(+), 27 deletions(-)

diff --git a/drivers/media/platform/vimc/vimc-capture.c b/drivers/media/platform/vimc/vimc-capture.c
index e7d0fc2228a6..2e5cf794f60f 100644
--- a/drivers/media/platform/vimc/vimc-capture.c
+++ b/drivers/media/platform/vimc/vimc-capture.c
@@ -22,6 +22,7 @@
#include <media/v4l2-ioctl.h>
#include <media/videobuf2-core.h>
#include <media/videobuf2-vmalloc.h>
+#include <media/media-dev-allocator.h>

#include "vimc-common.h"
#include "vimc-streamer.h"
@@ -72,6 +73,8 @@ struct vimc_cap_device {
struct mutex lock;
u32 sequence;
struct vimc_stream stream;
+ /* Used for holding reference to media dev allocated by vimc-core */
+ struct media_device *mdev;
};

static const struct v4l2_pix_format fmt_default = {
@@ -371,6 +374,7 @@ static void vimc_cap_release(struct video_device *vdev)
container_of(vdev, struct vimc_cap_device, vdev);

vimc_pads_cleanup(vcap->ved.pads);
+ media_device_delete(vcap->mdev, VIMC_CAP_DRV_NAME, THIS_MODULE);
kfree(vcap);
}

@@ -440,12 +444,21 @@ static int vimc_cap_comp_bind(struct device *comp, struct device *master,
if (!vcap)
return -ENOMEM;

+ /* first get reference to media device allocated by vimc */
+ vcap->mdev = media_device_allocate(master, NULL, NULL,
+ VIMC_CAP_DRV_NAME,
+ THIS_MODULE);
+ if (!vcap->mdev) {
+ ret = PTR_ERR(vcap->mdev);
+ goto err_free_vcap;
+ }
+
/* Allocate the pads */
vcap->ved.pads =
vimc_pads_init(1, (const unsigned long[1]) {MEDIA_PAD_FL_SINK});
if (IS_ERR(vcap->ved.pads)) {
ret = PTR_ERR(vcap->ved.pads);
- goto err_free_vcap;
+ goto err_mdev_rls_ref;
}

/* Initialize the media entity */
@@ -524,6 +537,8 @@ static int vimc_cap_comp_bind(struct device *comp, struct device *master,
media_entity_cleanup(&vcap->vdev.entity);
err_clean_pads:
vimc_pads_cleanup(vcap->ved.pads);
+err_mdev_rls_ref:
+ media_device_delete(vcap->mdev, VIMC_CAP_DRV_NAME, THIS_MODULE);
err_free_vcap:
kfree(vcap);

diff --git a/drivers/media/platform/vimc/vimc-core.c b/drivers/media/platform/vimc/vimc-core.c
index 3aa62d7e3d0e..d381993f3d7e 100644
--- a/drivers/media/platform/vimc/vimc-core.c
+++ b/drivers/media/platform/vimc/vimc-core.c
@@ -20,6 +20,7 @@
#include <linux/module.h>
#include <linux/platform_device.h>
#include <media/media-device.h>
+#include <media/media-dev-allocator.h>
#include <media/v4l2-device.h>

#include "vimc-common.h"
@@ -42,7 +43,7 @@ struct vimc_device {
const struct vimc_pipeline_config *pipe_cfg;

/* The Associated media_device parent */
- struct media_device mdev;
+ struct media_device *mdev;

/* Internal v4l2 parent device*/
struct v4l2_device v4l2_dev;
@@ -182,9 +183,9 @@ static int vimc_comp_bind(struct device *master)
dev_dbg(master, "bind");

/* Register the v4l2 struct */
- ret = v4l2_device_register(vimc->mdev.dev, &vimc->v4l2_dev);
+ ret = v4l2_device_register(vimc->mdev->dev, &vimc->v4l2_dev);
if (ret) {
- dev_err(vimc->mdev.dev,
+ dev_err(vimc->mdev->dev,
"v4l2 device register failed (err=%d)\n", ret);
return ret;
}
@@ -200,9 +201,9 @@ static int vimc_comp_bind(struct device *master)
goto err_comp_unbind_all;

/* Register the media device */
- ret = media_device_register(&vimc->mdev);
+ ret = media_device_register(vimc->mdev);
if (ret) {
- dev_err(vimc->mdev.dev,
+ dev_err(vimc->mdev->dev,
"media device register failed (err=%d)\n", ret);
goto err_comp_unbind_all;
}
@@ -210,7 +211,7 @@ static int vimc_comp_bind(struct device *master)
/* Expose all subdev's nodes*/
ret = v4l2_device_register_subdev_nodes(&vimc->v4l2_dev);
if (ret) {
- dev_err(vimc->mdev.dev,
+ dev_err(vimc->mdev->dev,
"vimc subdev nodes registration failed (err=%d)\n",
ret);
goto err_mdev_unregister;
@@ -219,8 +220,7 @@ static int vimc_comp_bind(struct device *master)
return 0;

err_mdev_unregister:
- media_device_unregister(&vimc->mdev);
- media_device_cleanup(&vimc->mdev);
+ media_device_delete(vimc->mdev, VIMC_PDEV_NAME, THIS_MODULE);
err_comp_unbind_all:
component_unbind_all(master, NULL);
err_v4l2_unregister:
@@ -236,8 +236,7 @@ static void vimc_comp_unbind(struct device *master)

dev_dbg(master, "unbind");

- media_device_unregister(&vimc->mdev);
- media_device_cleanup(&vimc->mdev);
+ media_device_delete(vimc->mdev, VIMC_PDEV_NAME, THIS_MODULE);
component_unbind_all(master, NULL);
v4l2_device_unregister(&vimc->v4l2_dev);
}
@@ -301,42 +300,51 @@ static int vimc_probe(struct platform_device *pdev)
struct vimc_device *vimc = container_of(pdev, struct vimc_device, pdev);
struct component_match *match = NULL;
int ret;
+ char bus_info[32]; /* same size as struct media_device bus_info */

dev_dbg(&pdev->dev, "probe");

- memset(&vimc->mdev, 0, sizeof(vimc->mdev));
+ /* Initialize media device */
+ snprintf(bus_info, sizeof(bus_info), "platform:%s", VIMC_PDEV_NAME);
+ vimc->mdev = media_device_allocate(&pdev->dev,
+ VIMC_MDEV_MODEL_NAME,
+ bus_info,
+ VIMC_PDEV_NAME,
+ THIS_MODULE);
+ if (!vimc->mdev)
+ return -ENOMEM;

/* Create platform_device for each entity in the topology*/
vimc->subdevs = devm_kcalloc(&vimc->pdev.dev, vimc->pipe_cfg->num_ents,
sizeof(*vimc->subdevs), GFP_KERNEL);
- if (!vimc->subdevs)
- return -ENOMEM;
+ if (!vimc->subdevs) {
+ ret = -ENOMEM;
+ goto err_delete_media_device;
+ }

match = vimc_add_subdevs(vimc);
- if (IS_ERR(match))
- return PTR_ERR(match);
+ if (IS_ERR(match)) {
+ ret = PTR_ERR(match);
+ goto err_delete_media_device;
+ }

/* Link the media device within the v4l2_device */
- vimc->v4l2_dev.mdev = &vimc->mdev;
-
- /* Initialize media device */
- strscpy(vimc->mdev.model, VIMC_MDEV_MODEL_NAME,
- sizeof(vimc->mdev.model));
- snprintf(vimc->mdev.bus_info, sizeof(vimc->mdev.bus_info),
- "platform:%s", VIMC_PDEV_NAME);
- vimc->mdev.dev = &pdev->dev;
- media_device_init(&vimc->mdev);
+ vimc->v4l2_dev.mdev = vimc->mdev;

/* Add self to the component system */
ret = component_master_add_with_match(&pdev->dev, &vimc_comp_ops,
match);
if (ret) {
- media_device_cleanup(&vimc->mdev);
vimc_rm_subdevs(vimc);
- return ret;
+ goto err_delete_media_device;
}

return 0;
+
+err_delete_media_device:
+ media_device_delete(vimc->mdev, VIMC_PDEV_NAME, THIS_MODULE);
+
+ return ret;
}

static int vimc_remove(struct platform_device *pdev)
--
2.17.1
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