2018-04-09 21:11:05

by Laura Abbott

Subject: [PATCH] drm/gma500: Remove VLA

There's an ongoing effort to remove VLAs[1] from the kernel to eventually
turn on -Wvla. Switch to a reasonable upper bound for the VLAs in
the gma500 driver.

[1] https://lkml.org/lkml/2018/3/7/621

Signed-off-by: Laura Abbott <[email protected]>
---
This was a little hard to figure out but I think 32 should be a
comfortable upper bound based on all the structures I saw. Of course I
can't test it.
---
drivers/gpu/drm/gma500/psb_intel_sdvo.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/gma500/psb_intel_sdvo.c b/drivers/gpu/drm/gma500/psb_intel_sdvo.c
index 84507912be84..3d4fa9f6b94c 100644
--- a/drivers/gpu/drm/gma500/psb_intel_sdvo.c
+++ b/drivers/gpu/drm/gma500/psb_intel_sdvo.c
@@ -429,13 +429,20 @@ static const char *cmd_status_names[] = {
"Scaling not supported"
};

+#define MAX_ARG_LEN 32
+
static bool psb_intel_sdvo_write_cmd(struct psb_intel_sdvo *psb_intel_sdvo, u8 cmd,
const void *args, int args_len)
{
- u8 buf[args_len*2 + 2], status;
- struct i2c_msg msgs[args_len + 3];
+ u8 buf[MAX_ARG_LEN*2 + 2], status;
+ struct i2c_msg msgs[MAX_ARG_LEN + 3];
int i, ret;

+ if (args_len > MAX_ARG_LEN) {
+ DRM_ERROR("Need to increase arg length\n");
+ return false;
+ }
+
psb_intel_sdvo_debug_write(psb_intel_sdvo, cmd, args, args_len);

for (i = 0; i < args_len; i++) {
--
2.14.3

2018-05-18 18:00:49

by Kees Cook

Subject: Re: [PATCH] drm/gma500: Remove VLA

On Mon, Apr 9, 2018 at 2:06 PM, Laura Abbott <[email protected]> wrote:
>
> There's an ongoing effort to remove VLAs[1] from the kernel to eventually
> turn on -Wvla. Switch to a reasonable upper bound for the VLAs in
> the gma500 driver.
>
> [1] https://lkml.org/lkml/2018/3/7/621
>
> Signed-off-by: Laura Abbott <[email protected]>

Reviewed-by: Kees Cook <[email protected]>

Daniel, can this go via you, or what's the best path for this patch?

Thanks!

-Kees

> ---
> This was a little hard to figure out but I think 32 should be a
> comfortable upper bound based on all the structures I saw. Of course I
> can't test it.
> ---
> drivers/gpu/drm/gma500/psb_intel_sdvo.c | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/gma500/psb_intel_sdvo.c b/drivers/gpu/drm/gma500/psb_intel_sdvo.c
> index 84507912be84..3d4fa9f6b94c 100644
> --- a/drivers/gpu/drm/gma500/psb_intel_sdvo.c
> +++ b/drivers/gpu/drm/gma500/psb_intel_sdvo.c
> @@ -429,13 +429,20 @@ static const char *cmd_status_names[] = {
> "Scaling not supported"
> };
>
> +#define MAX_ARG_LEN 32
> +
> static bool psb_intel_sdvo_write_cmd(struct psb_intel_sdvo *psb_intel_sdvo, u8 cmd,
> const void *args, int args_len)
> {
> - u8 buf[args_len*2 + 2], status;
> - struct i2c_msg msgs[args_len + 3];
> + u8 buf[MAX_ARG_LEN*2 + 2], status;
> + struct i2c_msg msgs[MAX_ARG_LEN + 3];
> int i, ret;
>
> + if (args_len > MAX_ARG_LEN) {
> + DRM_ERROR("Need to increase arg length\n");
> + return false;
> + }
> +
> psb_intel_sdvo_debug_write(psb_intel_sdvo, cmd, args, args_len);
>
> for (i = 0; i < args_len; i++) {
> --
> 2.14.3
>



--
Kees Cook
Pixel Security

2018-05-23 08:46:57

by Daniel Vetter

Subject: Re: [PATCH] drm/gma500: Remove VLA

On Fri, May 18, 2018 at 10:58:40AM -0700, Kees Cook wrote:
> On Mon, Apr 9, 2018 at 2:06 PM, Laura Abbott <[email protected]> wrote:
> >
> > There's an ongoing effort to remove VLAs[1] from the kernel to eventually
> > turn on -Wvla. Switch to a reasonable upper bound for the VLAs in
> > the gma500 driver.
> >
> > [1] https://lkml.org/lkml/2018/3/7/621
> >
> > Signed-off-by: Laura Abbott <[email protected]>
>
> Reviewed-by: Kees Cook <[email protected]>
>
> Daniel, can this go via you, or what's the best path for this patch?

Applied to drm-misc-next for 4.19, thanks.
-Daniel

>
> Thanks!
>
> -Kees
>
> > ---
> > This was a little hard to figure out but I think 32 should be a
> > comfortable upper bound based on all the structures I saw. Of course I
> > can't test it.
> > ---
> > drivers/gpu/drm/gma500/psb_intel_sdvo.c | 11 +++++++++--
> > 1 file changed, 9 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/gma500/psb_intel_sdvo.c b/drivers/gpu/drm/gma500/psb_intel_sdvo.c
> > index 84507912be84..3d4fa9f6b94c 100644
> > --- a/drivers/gpu/drm/gma500/psb_intel_sdvo.c
> > +++ b/drivers/gpu/drm/gma500/psb_intel_sdvo.c
> > @@ -429,13 +429,20 @@ static const char *cmd_status_names[] = {
> > "Scaling not supported"
> > };
> >
> > +#define MAX_ARG_LEN 32
> > +
> > static bool psb_intel_sdvo_write_cmd(struct psb_intel_sdvo *psb_intel_sdvo, u8 cmd,
> > const void *args, int args_len)
> > {
> > - u8 buf[args_len*2 + 2], status;
> > - struct i2c_msg msgs[args_len + 3];
> > + u8 buf[MAX_ARG_LEN*2 + 2], status;
> > + struct i2c_msg msgs[MAX_ARG_LEN + 3];
> > int i, ret;
> >
> > + if (args_len > MAX_ARG_LEN) {
> > + DRM_ERROR("Need to increase arg length\n");
> > + return false;
> > + }
> > +
> > psb_intel_sdvo_debug_write(psb_intel_sdvo, cmd, args, args_len);
> >
> > for (i = 0; i < args_len; i++) {
> > --
> > 2.14.3
> >
>
>
>
> --
> Kees Cook
> Pixel Security

--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch