msm_vfe_register_entities loops through each Raw Data Interface input line. For each loop we add video device with its associated pads.
Once a single /dev/video0 node has been populated it is possible for camss_find_sensor_pad to run. This routine scans through a list of media entities taking a pointer pad = media_entity->pad[0] and assuming that pointer is always valid.
It is possible for both the enumeration loop in msm_vfe_register_entities() and a call from user-space to run concurrently.
Adding some deliberate sleep code into the loop in msm_vfe_register_entities() and constructing a user-space program to open every /dev/videoX node in a tight continuous loop, quickly shows the following error.
[ 691.074558] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000030 [ 691.074933] Call trace: [ 691.074935] camss_find_sensor_pad+0x74/0x114 [qcom_camss] (P) [ 691.074946] camss_get_pixel_clock+0x18/0x64 [qcom_camss] [ 691.074956] vfe_get+0xc0/0x54c [qcom_camss] [ 691.074968] vfe_set_power+0x58/0xf4c [qcom_camss] [ 691.074978] pipeline_pm_power_one+0x124/0x140 [videodev] [ 691.074986] pipeline_pm_power+0x70/0x100 [videodev] [ 691.074992] v4l2_pipeline_pm_use+0x54/0x90 [videodev] [ 691.074998] v4l2_pipeline_pm_get+0x14/0x20 [videodev] [ 691.075005] video_open+0x74/0xe0 [qcom_camss] [ 691.075014] v4l2_open+0xa8/0x124 [videodev] [ 691.075021] chrdev_open+0xb0/0x21c [ 691.075031] do_dentry_open+0x138/0x4c4 [ 691.075040] vfs_open+0x2c/0xe8 [ 691.075044] path_openat+0x6f0/0x10a0 [ 691.075050] do_filp_open+0xa8/0x164 [ 691.075054] do_sys_openat2+0x94/0x104 [ 691.075058] __arm64_sys_openat+0x64/0xc0 [ 691.075061] invoke_syscall+0x48/0x104 [ 691.075069] el0_svc_common.constprop.0+0x40/0xe0 [ 691.075075] do_el0_svc+0x1c/0x28 [ 691.075080] el0_svc+0x30/0xcc [ 691.075085] el0t_64_sync_handler+0x10c/0x138 [ 691.075088] el0t_64_sync+0x198/0x19c
Taking the vfe->power_lock is not possible since v4l2_device_register_subdev takes the mdev->graph_lock. Later on fops->open takes the mdev->graph_lock followed by vfe_get() -> taking vfe->power_lock.
Introduce a simple enumeration_complete bool which is false initially and only set true once in our init routine after we complete enumeration.
If user-space tries to interact with the VFE before complete enumeration it will receive -EAGAIN.
Cc: stable@vger.kernel.org Fixes: 4c98a5f57f90 ("media: camss: Add VFE files") Reported-by: Johan Hovold johan+linaro@kernel.org Closes: https://lore.kernel.org/all/Zwjw6XfVWcufMlqM@hovoldconsulting.com Signed-off-by: Bryan O'Donoghue bryan.odonoghue@linaro.org --- drivers/media/platform/qcom/camss/camss-vfe.c | 8 ++++++++ drivers/media/platform/qcom/camss/camss-vfe.h | 1 + 2 files changed, 9 insertions(+)
diff --git a/drivers/media/platform/qcom/camss/camss-vfe.c b/drivers/media/platform/qcom/camss/camss-vfe.c index ac3a9579e3e6910eee8c1ec11c4fff6e1bc94443..3fccc83ebbcc84c20e17da72c359de3dfd18fb40 100644 --- a/drivers/media/platform/qcom/camss/camss-vfe.c +++ b/drivers/media/platform/qcom/camss/camss-vfe.c @@ -1062,6 +1062,9 @@ int vfe_get(struct vfe_device *vfe) { int ret;
+ if (!vfe->enumeration_complete) + return -EAGAIN; + mutex_lock(&vfe->power_lock);
if (vfe->power_count == 0) { @@ -1122,6 +1125,9 @@ int vfe_get(struct vfe_device *vfe) */ void vfe_put(struct vfe_device *vfe) { + if (!vfe->enumeration_complete) + return; + mutex_lock(&vfe->power_lock);
if (vfe->power_count == 0) { @@ -2091,6 +2097,8 @@ int msm_vfe_register_entities(struct vfe_device *vfe, } }
+ vfe->enumeration_complete = true; + return 0;
error_link: diff --git a/drivers/media/platform/qcom/camss/camss-vfe.h b/drivers/media/platform/qcom/camss/camss-vfe.h index 614e932c33da78e02e0800ce6534af7b14822f83..33b59dcfc8b2b81e896336b079a41eba603ec400 100644 --- a/drivers/media/platform/qcom/camss/camss-vfe.h +++ b/drivers/media/platform/qcom/camss/camss-vfe.h @@ -169,6 +169,7 @@ struct vfe_device { struct camss_video_ops video_ops; struct device *genpd; struct device_link *genpd_link; + bool enumeration_complete; };
struct camss_subdev_resources;