2024-04-12 08:40:33

by Aleksandr Mishin

Subject: [PATCH v2] drm: bridge: cdns-mhdp8546: Fix possible null pointer dereference

In cdns_mhdp_atomic_enable(), the return value of drm_mode_duplicate() is
assigned to mhdp_state->current_mode, and there is a dereference of it in
drm_mode_set_name(), which will lead to a NULL pointer dereference on
failure of drm_mode_duplicate().

Fix this bug by adding a check of mhdp_state->current_mode.

Fixes: fb43aa0acdfd ("drm: bridge: Add support for Cadence MHDP8546 DPI/DP bridge")
Signed-off-by: Aleksandr Mishin <[email protected]>
---
v2: Fix a mistake where the mutex remained locked

drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
index e226acc5c15e..5b831d6d7764 100644
--- a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
+++ b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
@@ -2059,6 +2059,11 @@ static void cdns_mhdp_atomic_enable(struct drm_bridge *bridge,
mhdp_state = to_cdns_mhdp_bridge_state(new_state);

mhdp_state->current_mode = drm_mode_duplicate(bridge->dev, mode);
+ if (!mhdp_state->current_mode) {
+ ret = -EINVAL;
+ goto out;
+ }
+
drm_mode_set_name(mhdp_state->current_mode);

dev_dbg(mhdp->dev, "%s: Enabling mode %s\n", __func__, mode->name);
--
2.30.2

2024-04-16 13:35:32

by Robert Foss

Subject: Re: [PATCH v2] drm: bridge: cdns-mhdp8546: Fix possible null pointer dereference

Hey Aleksandr,

On Fri, Apr 12, 2024 at 10:40 AM Aleksandr Mishin <[email protected]> wrote:
>
> In cdns_mhdp_atomic_enable(), the return value of drm_mode_duplicate() is
> assigned to mhdp_state->current_mode, and there is a dereference of it in
> drm_mode_set_name(), which will lead to a NULL pointer dereference on
> failure of drm_mode_duplicate().
>
> Fix this bug by adding a check of mhdp_state->current_mode.
>
> Fixes: fb43aa0acdfd ("drm: bridge: Add support for Cadence MHDP8546 DPI/DP bridge")
> Signed-off-by: Aleksandr Mishin <[email protected]>
> ---
> v2: Fix a mistake where the mutex remained locked
>
> drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
> index e226acc5c15e..5b831d6d7764 100644
> --- a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
> +++ b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
> @@ -2059,6 +2059,11 @@ static void cdns_mhdp_atomic_enable(struct drm_bridge *bridge,
> mhdp_state = to_cdns_mhdp_bridge_state(new_state);
>
> mhdp_state->current_mode = drm_mode_duplicate(bridge->dev, mode);
> + if (!mhdp_state->current_mode) {
> + ret = -EINVAL;
> + goto out;
> + }
> +

This chunk no longer applies on drm-misc-next.

I think the approach here is still better than what is in
drm-misc-next since it unlocks link_mutex.

Can you rebase + reword the commit message and send that out as v3?

> drm_mode_set_name(mhdp_state->current_mode);
>
> dev_dbg(mhdp->dev, "%s: Enabling mode %s\n", __func__, mode->name);
> --
> 2.30.2
>