In komeda_plane_add(), komeda_get_layer_fourcc_list() is assigned to
formats and used in drm_universal_plane_init().
drm_universal_plane_init() passes formats to
__drm_universal_plane_init(). __drm_universal_plane_init() further
passes formats to memcpy() as src parameter, which could lead to an
undefined behavior bug on failure of komeda_get_layer_fourcc_list().
Fix this bug by adding a check of formats.
This bug was found by a static analyzer. The analysis employs
differential checking to identify inconsistent security operations
(e.g., checks or kfrees) between two code paths and confirms that the
inconsistent operations are not recovered in the current function or
the callers, so they constitute bugs.
Note that, as a bug found by static analysis, it can be a false
positive or hard to trigger. Multiple researchers have cross-reviewed
the bug.
Builds with CONFIG_DRM_KOMEDA=m show no new warnings,
and our static analyzer no longer warns about this code.
Fixes: 61f1c4a8ab75 ("drm/komeda: Attach komeda_dev to DRM-KMS")
Signed-off-by: Zhou Qingyang <[email protected]>
---
drivers/gpu/drm/arm/display/komeda/komeda_plane.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/drivers/gpu/drm/arm/display/komeda/komeda_plane.c b/drivers/gpu/drm/arm/display/komeda/komeda_plane.c
index d63d83800a8a..dd3f17e970dd 100644
--- a/drivers/gpu/drm/arm/display/komeda/komeda_plane.c
+++ b/drivers/gpu/drm/arm/display/komeda/komeda_plane.c
@@ -265,6 +265,10 @@ static int komeda_plane_add(struct komeda_kms_dev *kms,
formats = komeda_get_layer_fourcc_list(&mdev->fmt_tbl,
layer->layer_type, &n_formats);
+ if (!formats) {
+ err = -ENOMEM;
+ goto cleanup;
+ }
err = drm_universal_plane_init(&kms->base, plane,
get_possible_crtcs(kms, c->pipeline),
--
2.25.1
Hi Zhou,
On Tue, Nov 30, 2021 at 10:23:01PM +0800, Zhou Qingyang wrote:
> In komeda_plane_add(), komeda_get_layer_fourcc_list() is assigned to
> formats and used in drm_universal_plane_init().
> drm_universal_plane_init() passes formats to
> __drm_universal_plane_init(). __drm_universal_plane_init() further
> passes formats to memcpy() as src parameter, which could lead to an
> undefined behavior bug on failure of komeda_get_layer_fourcc_list().
>
> Fix this bug by adding a check of formats.
>
> This bug was found by a static analyzer. The analysis employs
> differential checking to identify inconsistent security operations
> (e.g., checks or kfrees) between two code paths and confirms that the
> inconsistent operations are not recovered in the current function or
> the callers, so they constitute bugs.
>
> Note that, as a bug found by static analysis, it can be a false
> positive or hard to trigger. Multiple researchers have cross-reviewed
> the bug.
If multiple researchers have cross-reviewed the bug how many have reviewed the fix?
I'm asking because there is a problem with the fix ....
>
> Builds with CONFIG_DRM_KOMEDA=m show no new warnings,
> and our static analyzer no longer warns about this code.
>
> Fixes: 61f1c4a8ab75 ("drm/komeda: Attach komeda_dev to DRM-KMS")
> Signed-off-by: Zhou Qingyang <[email protected]>
> ---
> drivers/gpu/drm/arm/display/komeda/komeda_plane.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/gpu/drm/arm/display/komeda/komeda_plane.c b/drivers/gpu/drm/arm/display/komeda/komeda_plane.c
> index d63d83800a8a..dd3f17e970dd 100644
> --- a/drivers/gpu/drm/arm/display/komeda/komeda_plane.c
> +++ b/drivers/gpu/drm/arm/display/komeda/komeda_plane.c
> @@ -265,6 +265,10 @@ static int komeda_plane_add(struct komeda_kms_dev *kms,
>
> formats = komeda_get_layer_fourcc_list(&mdev->fmt_tbl,
> layer->layer_type, &n_formats);
> + if (!formats) {
> + err = -ENOMEM;
> + goto cleanup;
If you go to cleanup here it is too early, as the plane variable has not been
initialised by the drm_universal_plane_init(), so komeda_plane_destroy() will crash.
The correct fix here is to free the kplane allocation and then return -ENOMEM.
> + }
>
> err = drm_universal_plane_init(&kms->base, plane,
> get_possible_crtcs(kms, c->pipeline),
> --
> 2.25.1
>
Best regards,
Liviu
--
====================
| I would like to |
| fix the world, |
| but they're not |
| giving me the |
\ source code! /
---------------
¯\_(ツ)_/¯
In komeda_plane_add(), komeda_get_layer_fourcc_list() is assigned to
formats and used in drm_universal_plane_init().
drm_universal_plane_init() passes formats to
__drm_universal_plane_init(). __drm_universal_plane_init() further
passes formats to memcpy() as src parameter, which could lead to an
undefined behavior bug on failure of komeda_get_layer_fourcc_list().
Fix this bug by adding a check of formats.
This bug was found by a static analyzer. The analysis employs
differential checking to identify inconsistent security operations
(e.g., checks or kfrees) between two code paths and confirms that the
inconsistent operations are not recovered in the current function or
the callers, so they constitute bugs.
Note that, as a bug found by static analysis, it can be a false
positive or hard to trigger. Multiple researchers have cross-reviewed
the bug.
Builds with CONFIG_DRM_KOMEDA=m show no new warnings,
and our static analyzer no longer warns about this code.
Fixes: 61f1c4a8ab75 ("drm/komeda: Attach komeda_dev to DRM-KMS")
Signed-off-by: Zhou Qingyang <[email protected]>
---
Changes in v2
- Use kfree and return instead of using 'goto'
drivers/gpu/drm/arm/display/komeda/komeda_plane.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/drivers/gpu/drm/arm/display/komeda/komeda_plane.c b/drivers/gpu/drm/arm/display/komeda/komeda_plane.c
index d63d83800a8a..aa193c58f4bf 100644
--- a/drivers/gpu/drm/arm/display/komeda/komeda_plane.c
+++ b/drivers/gpu/drm/arm/display/komeda/komeda_plane.c
@@ -265,6 +265,10 @@ static int komeda_plane_add(struct komeda_kms_dev *kms,
formats = komeda_get_layer_fourcc_list(&mdev->fmt_tbl,
layer->layer_type, &n_formats);
+ if (!formats) {
+ kfree(kplane);
+ return -ENOMEM;
+ }
err = drm_universal_plane_init(&kms->base, plane,
get_possible_crtcs(kms, c->pipeline),
--
2.25.1
On Wed, Dec 01, 2021 at 11:37:03AM +0800, Zhou Qingyang wrote:
> In komeda_plane_add(), komeda_get_layer_fourcc_list() is assigned to
> formats and used in drm_universal_plane_init().
> drm_universal_plane_init() passes formats to
> __drm_universal_plane_init(). __drm_universal_plane_init() further
> passes formats to memcpy() as src parameter, which could lead to an
> undefined behavior bug on failure of komeda_get_layer_fourcc_list().
>
> Fix this bug by adding a check of formats.
>
> This bug was found by a static analyzer. The analysis employs
> differential checking to identify inconsistent security operations
> (e.g., checks or kfrees) between two code paths and confirms that the
> inconsistent operations are not recovered in the current function or
> the callers, so they constitute bugs.
>
> Note that, as a bug found by static analysis, it can be a false
> positive or hard to trigger. Multiple researchers have cross-reviewed
> the bug.
>
> Builds with CONFIG_DRM_KOMEDA=m show no new warnings,
> and our static analyzer no longer warns about this code.
>
> Fixes: 61f1c4a8ab75 ("drm/komeda: Attach komeda_dev to DRM-KMS")
> Signed-off-by: Zhou Qingyang <[email protected]>
Thanks for the fix!
Reviewed-by: Liviu Dudau <[email protected]>
Best regards,
Liviu
> ---
> Changes in v2
> - Use kfree and return instead of using 'goto'
>
> drivers/gpu/drm/arm/display/komeda/komeda_plane.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/gpu/drm/arm/display/komeda/komeda_plane.c b/drivers/gpu/drm/arm/display/komeda/komeda_plane.c
> index d63d83800a8a..aa193c58f4bf 100644
> --- a/drivers/gpu/drm/arm/display/komeda/komeda_plane.c
> +++ b/drivers/gpu/drm/arm/display/komeda/komeda_plane.c
> @@ -265,6 +265,10 @@ static int komeda_plane_add(struct komeda_kms_dev *kms,
>
> formats = komeda_get_layer_fourcc_list(&mdev->fmt_tbl,
> layer->layer_type, &n_formats);
> + if (!formats) {
> + kfree(kplane);
> + return -ENOMEM;
> + }
>
> err = drm_universal_plane_init(&kms->base, plane,
> get_possible_crtcs(kms, c->pipeline),
> --
> 2.25.1
>
--
====================
| I would like to |
| fix the world, |
| but they're not |
| giving me the |
\ source code! /
---------------
¯\_(ツ)_/¯