Sergey Suloev reported a crash happening in drm_client_dev_hotplug()
when fbdev had failed to register.
[ 9.124598] vc4_hdmi 3f902000.hdmi: ASoC: Failed to create
component debugfs directory
[ 9.147667] vc4_hdmi 3f902000.hdmi: vc4-hdmi-hifi <->
3f902000.hdmi mapping ok
[ 9.155184] vc4_hdmi 3f902000.hdmi: ASoC: no DMI vendor name!
[ 9.166544] vc4-drm soc:gpu: bound 3f902000.hdmi (ops vc4_hdmi_ops
[vc4])
[ 9.173840] vc4-drm soc:gpu: bound 3f806000.vec (ops vc4_vec_ops
[vc4])
[ 9.181029] vc4-drm soc:gpu: bound 3f004000.txp (ops vc4_txp_ops
[vc4])
[ 9.188519] vc4-drm soc:gpu: bound 3f400000.hvs (ops vc4_hvs_ops
[vc4])
[ 9.195690] vc4-drm soc:gpu: bound 3f206000.pixelvalve (ops
vc4_crtc_ops [vc4])
[ 9.203523] vc4-drm soc:gpu: bound 3f207000.pixelvalve (ops
vc4_crtc_ops [vc4])
[ 9.215032] vc4-drm soc:gpu: bound 3f807000.pixelvalve (ops
vc4_crtc_ops [vc4])
[ 9.274785] vc4-drm soc:gpu: bound 3fc00000.v3d (ops vc4_v3d_ops
[vc4])
[ 9.290246] [drm] Initialized vc4 0.0.0 20140616 for soc:gpu on
minor 0
[ 9.297464] [drm] Supports vblank timestamp caching Rev 2
(21.10.2013).
[ 9.304600] [drm] Driver supports precise vblank timestamp query.
[ 9.382856] vc4-drm soc:gpu: [drm:drm_fb_helper_fbdev_setup
[drm_kms_helper]] *ERROR* Failed to set fbdev configuration
[ 10.404937] Unable to handle kernel paging request at virtual
address 00330a656369768a
[ 10.441620] [00330a656369768a] address between user and kernel
address ranges
[ 10.449087] Internal error: Oops: 96000004 [#1] PREEMPT SMP
[ 10.454762] Modules linked in: brcmfmac vc4 drm_kms_helper
cfg80211 drm rfkill smsc95xx brcmutil usbnet
drm_panel_orientation_quirks raspberrypi_hwmon bcm2835_dma crc32_ce
pwm_bcm2835 bcm2835_rng virt_dma rng_core i2c_bcm2835 ip_tables
x_tables ipv6
[ 10.477296] CPU: 2 PID: 45 Comm: kworker/2:1 Not tainted
4.19.0-rc5 #3
[ 10.483934] Hardware name: Raspberry Pi 3 Model B Rev 1.2 (DT)
[ 10.489966] Workqueue: events output_poll_execute [drm_kms_helper]
[ 10.596515] Process kworker/2:1 (pid: 45, stack limit =
0x000000007e8924dc)
[ 10.603590] Call trace:
[ 10.606259] drm_client_dev_hotplug+0x5c/0xb0 [drm]
[ 10.611303] drm_kms_helper_hotplug_event+0x30/0x40 [drm_kms_helper]
[ 10.617849] output_poll_execute+0xc4/0x1e0 [drm_kms_helper]
[ 10.623616] process_one_work+0x1c8/0x318
[ 10.627695] worker_thread+0x48/0x428
[ 10.631420] kthread+0xf8/0x128
[ 10.634615] ret_from_fork+0x10/0x18
[ 10.638255] Code: 54000220 f9401261 aa1303e0 b4000141 (f9400c21)
[ 10.644456] ---[ end trace c75b4a4b0e141908 ]---
The reason for this is that drm_fbdev_cma_init() removes the drm_client
when fbdev registration fails, but it doesn't remove the client from the
drm_device client list. So the client list now has a pointer that points
into the unknown and we have a 'use after free' situation.
Split drm_client_new() into drm_client_init() and drm_client_add() to
fix
removal in the error path.
Fixes: 894a677f4b3e ("drm/cma-helper: Use the generic fbdev emulation")
Reported-by: Sergey Suloev <ssuloev@xxxxxxxxxxxxx>
Cc: Stefan Wahren <stefan.wahren@xxxxxxxx>
Cc: Eric Anholt <eric@xxxxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
Signed-off-by: Noralf Trønnes <noralf@xxxxxxxxxxx>
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
---
Changes since version 2:
- Fix drm_client_new() ref in docs (Daniel)
- Expand drm_client_add() docs (Daniel)
Changes since version 1:
- Split drm_client_new() instead of letting drm_client hang around
(Daniel)
drivers/gpu/drm/drm_client.c | 35
++++++++++++++++++++++++++---------
drivers/gpu/drm/drm_fb_cma_helper.c | 4 +++-
drivers/gpu/drm/drm_fb_helper.c | 4 +++-
include/drm/drm_client.h | 5 +++--
4 files changed, 35 insertions(+), 13 deletions(-)
diff --git a/drivers/gpu/drm/drm_client.c b/drivers/gpu/drm/drm_client.c
index 17d9a64e885e..fc03d26fcacc 100644
--- a/drivers/gpu/drm/drm_client.c
+++ b/drivers/gpu/drm/drm_client.c
@@ -63,20 +63,21 @@ static void drm_client_close(struct
drm_client_dev *client)
EXPORT_SYMBOL(drm_client_close);
/**
- * drm_client_new - Create a DRM client
+ * drm_client_init - Initialise a DRM client
* @dev: DRM device
* @client: DRM client
* @name: Client name
* @funcs: DRM client functions (optional)
*
+ * This initialises the client and opens a &drm_file. Use
drm_client_add() to complete the process.
* The caller needs to hold a reference on @dev before calling this
function.
* The client is freed when the &drm_device is unregistered. See
drm_client_release().
*
* Returns:
* Zero on success or negative error code on failure.
*/
-int drm_client_new(struct drm_device *dev, struct drm_client_dev
*client,
- const char *name, const struct drm_client_funcs *funcs)
+int drm_client_init(struct drm_device *dev, struct drm_client_dev
*client,
+ const char *name, const struct drm_client_funcs *funcs)
{
int ret;
@@ -95,10 +96,6 @@ int drm_client_new(struct drm_device *dev,
struct drm_client_dev *client,
if (ret)
goto err_put_module;
- mutex_lock(&dev->clientlist_mutex);
- list_add(&client->list, &dev->clientlist);
- mutex_unlock(&dev->clientlist_mutex);
-
drm_dev_get(dev);
return 0;
@@ -109,13 +106,33 @@ int drm_client_new(struct drm_device *dev,
struct drm_client_dev *client,
return ret;
}
-EXPORT_SYMBOL(drm_client_new);
+EXPORT_SYMBOL(drm_client_init);
+
+/**
+ * drm_client_add - Add client to the device list
+ * @client: DRM client
+ *
+ * Add the client to the &drm_device client list to activate its
callbacks.
+ * @client must be initialized by a call to drm_client_init(). After
+ * drm_client_add() it is no longer permissible to call
drm_client_release()
+ * directly (outside the unregister callback), instead cleanup will
happen
+ * automatically on driver unload.
+ */
+void drm_client_add(struct drm_client_dev *client)
+{
+ struct drm_device *dev = client->dev;
+
+ mutex_lock(&dev->clientlist_mutex);
+ list_add(&client->list, &dev->clientlist);
+ mutex_unlock(&dev->clientlist_mutex);
+}
+EXPORT_SYMBOL(drm_client_add);
/**
* drm_client_release - Release DRM client resources
* @client: DRM client
*
- * Releases resources by closing the &drm_file that was opened by
drm_client_new().
+ * Releases resources by closing the &drm_file that was opened by
drm_client_init().
* It is called automatically if the &drm_client_funcs.unregister
callback is _not_ set.
*
* This function should only be called from the unregister
callback. An exception
diff --git a/drivers/gpu/drm/drm_fb_cma_helper.c
b/drivers/gpu/drm/drm_fb_cma_helper.c
index 47e0e2f6642d..fb0dfc62b1b6 100644
--- a/drivers/gpu/drm/drm_fb_cma_helper.c
+++ b/drivers/gpu/drm/drm_fb_cma_helper.c
@@ -167,7 +167,7 @@ struct drm_fbdev_cma *drm_fbdev_cma_init(struct
drm_device *dev,
fb_helper = &fbdev_cma->fb_helper;
- ret = drm_client_new(dev, &fb_helper->client, "fbdev", NULL);
+ ret = drm_client_init(dev, &fb_helper->client, "fbdev", NULL);
if (ret)
goto err_free;
@@ -176,6 +176,8 @@ struct drm_fbdev_cma *drm_fbdev_cma_init(struct
drm_device *dev,
if (ret)
goto err_client_put;
+ drm_client_add(&fb_helper->client);
+
return fbdev_cma;
err_client_put:
diff --git a/drivers/gpu/drm/drm_fb_helper.c
b/drivers/gpu/drm/drm_fb_helper.c
index a504a5e05676..e9095537e0c0 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -3229,13 +3229,15 @@ int drm_fbdev_generic_setup(struct drm_device
*dev, unsigned int preferred_bpp)
if (!fb_helper)
return -ENOMEM;
- ret = drm_client_new(dev, &fb_helper->client, "fbdev",
&drm_fbdev_client_funcs);
+ ret = drm_client_init(dev, &fb_helper->client, "fbdev",
&drm_fbdev_client_funcs);
if (ret) {
kfree(fb_helper);
DRM_DEV_ERROR(dev->dev, "Failed to register client: %d\n",
ret);
return ret;
}
+ drm_client_add(&fb_helper->client);
+
fb_helper->preferred_bpp = preferred_bpp;
ret = drm_fbdev_client_hotplug(&fb_helper->client);
diff --git a/include/drm/drm_client.h b/include/drm/drm_client.h
index 989f8e52864d..971bb7853776 100644
--- a/include/drm/drm_client.h
+++ b/include/drm/drm_client.h
@@ -87,9 +87,10 @@ struct drm_client_dev {
struct drm_file *file;
};
-int drm_client_new(struct drm_device *dev, struct drm_client_dev
*client,
- const char *name, const struct drm_client_funcs *funcs);
+int drm_client_init(struct drm_device *dev, struct drm_client_dev
*client,
+ const char *name, const struct drm_client_funcs *funcs);
void drm_client_release(struct drm_client_dev *client);
+void drm_client_add(struct drm_client_dev *client);
void drm_client_dev_unregister(struct drm_device *dev);
void drm_client_dev_hotplug(struct drm_device *dev);
