[PATCH 1/1] drm/gma500: mdfld: avoid possible null pointer dereference

[PATCH 1/1] drm/gma500: mdfld: avoid possible null pointer dereference

[Heinrich Schuchardt]

Only dereference sender after checking if sender is NULL.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
---
 drivers/gpu/drm/gma500/mdfld_dsi_pkg_sender.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/gma500/mdfld_dsi_pkg_sender.c b/drivers/gpu/drm/gma500/mdfld_dsi_pkg_sender.c
index 1616af2..c50534c 100644
--- a/drivers/gpu/drm/gma500/mdfld_dsi_pkg_sender.c
+++ b/drivers/gpu/drm/gma500/mdfld_dsi_pkg_sender.c
@@ -520,7 +520,7 @@ static int __read_panel_data(struct mdfld_dsi_pkg_sender *sender, u8 data_type,
 			u8 *data, u16 len, u32 *data_out, u16 len_out, bool hs)
 {
 	unsigned long flags;
-	struct drm_device *dev = sender->dev;
+	struct drm_device *dev;
 	int i;
 	u32 gen_data_reg;
 	int retry = MDFLD_DSI_READ_MAX_COUNT;
@@ -530,6 +530,8 @@ static int __read_panel_data(struct mdfld_dsi_pkg_sender *sender, u8 data_type,
 		return -EINVAL;
 	}
 
+	dev = sender->dev;
+
 	/**
 	 * do reading.
 	 * 0) send out generic read request
-- 
2.1.4

Re: [PATCH 1/1] drm/gma500: mdfld: avoid possible null pointer dereference

[Patrik Jakobsson]

On Wed, May 18, 2016 at 10:31 PM, Heinrich Schuchardt
<xypron.glpk@gmx.de> wrote:
> Only dereference sender after checking if sender is NULL.

Hi Heinrich

I think we had a patch that did something similar a while ago. Don't
remember what happened to it. We do check for !sender right before
calling this function (at only one call-site) so it cannot be NULL at
this point. I would be ok with your change if you also remove the
extra checks in mdfld_dsi_read_mcs(). That way we don't double check
and we check at the point where it actually matters.

Thanks
Patrik

>
> Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
> ---
>  drivers/gpu/drm/gma500/mdfld_dsi_pkg_sender.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/gma500/mdfld_dsi_pkg_sender.c b/drivers/gpu/drm/gma500/mdfld_dsi_pkg_sender.c
> index 1616af2..c50534c 100644
> --- a/drivers/gpu/drm/gma500/mdfld_dsi_pkg_sender.c
> +++ b/drivers/gpu/drm/gma500/mdfld_dsi_pkg_sender.c
> @@ -520,7 +520,7 @@ static int __read_panel_data(struct mdfld_dsi_pkg_sender *sender, u8 data_type,
>                         u8 *data, u16 len, u32 *data_out, u16 len_out, bool hs)
>  {
>         unsigned long flags;
> -       struct drm_device *dev = sender->dev;
> +       struct drm_device *dev;
>         int i;
>         u32 gen_data_reg;
>         int retry = MDFLD_DSI_READ_MAX_COUNT;
> @@ -530,6 +530,8 @@ static int __read_panel_data(struct mdfld_dsi_pkg_sender *sender, u8 data_type,
>                 return -EINVAL;
>         }
>
> +       dev = sender->dev;
> +
>         /**
>          * do reading.
>          * 0) send out generic read request
> --
> 2.1.4
>

Re: [PATCH 1/1] drm/gma500: mdfld: avoid possible null pointer dereference

[Patrik Jakobsson]

On Wed, May 18, 2016 at 10:31 PM, Heinrich Schuchardt
<xypron.glpk@gmx.de> wrote:
> Only dereference sender after checking if sender is NULL.

Hi Heinrich

I think we had a patch that did something similar a while ago. Don't
remember what happened to it. We do check for !sender right before
calling this function (at only one call-site) so it cannot be NULL at
this point. I would be ok with your change if you also remove the
extra checks in mdfld_dsi_read_mcs(). That way we don't double check
and we check at the point where it actually matters.

Thanks
Patrik

>
> Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
> ---
>  drivers/gpu/drm/gma500/mdfld_dsi_pkg_sender.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/gma500/mdfld_dsi_pkg_sender.c b/drivers/gpu/drm/gma500/mdfld_dsi_pkg_sender.c
> index 1616af2..c50534c 100644
> --- a/drivers/gpu/drm/gma500/mdfld_dsi_pkg_sender.c
> +++ b/drivers/gpu/drm/gma500/mdfld_dsi_pkg_sender.c
> @@ -520,7 +520,7 @@ static int __read_panel_data(struct mdfld_dsi_pkg_sender *sender, u8 data_type,
>                         u8 *data, u16 len, u32 *data_out, u16 len_out, bool hs)
>  {
>         unsigned long flags;
> -       struct drm_device *dev = sender->dev;
> +       struct drm_device *dev;
>         int i;
>         u32 gen_data_reg;
>         int retry = MDFLD_DSI_READ_MAX_COUNT;
> @@ -530,6 +530,8 @@ static int __read_panel_data(struct mdfld_dsi_pkg_sender *sender, u8 data_type,
>                 return -EINVAL;
>         }
>
> +       dev = sender->dev;
> +
>         /**
>          * do reading.
>          * 0) send out generic read request
> --
> 2.1.4
>
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