2019-10-18 22:32:59

by Kangjie Lu

Subject: [PATCH] gma/gma500: fix a memory disclosure bug due to uninitialized bytes

`best_clock` is an object that may be sent out. Object `clock`
contains uninitialized bytes that are copied to `best_clock`,
which leads to memory disclosure and information leak.

Signed-off-by: Kangjie Lu <[email protected]>
---
drivers/gpu/drm/gma500/cdv_intel_display.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/gma500/cdv_intel_display.c b/drivers/gpu/drm/gma500/cdv_intel_display.c
index f56852a503e8..8b784947ed3b 100644
--- a/drivers/gpu/drm/gma500/cdv_intel_display.c
+++ b/drivers/gpu/drm/gma500/cdv_intel_display.c
@@ -405,6 +405,8 @@ static bool cdv_intel_find_dp_pll(const struct gma_limit_t *limit,
struct gma_crtc *gma_crtc = to_gma_crtc(crtc);
struct gma_clock_t clock;

+ memset(&clock, 0, sizeof(clock));
+
switch (refclk) {
case 27000:
if (target < 200000) {
--
2.17.1

2019-10-22 08:58:14

by Daniel Vetter

Subject: Re: [PATCH] gma/gma500: fix a memory disclosure bug due to uninitialized bytes

On Thu, Oct 17, 2019 at 11:29:53PM -0500, Kangjie Lu wrote:
> `best_clock` is an object that may be sent out. Object `clock`
> contains uninitialized bytes that are copied to `best_clock`,
> which leads to memory disclosure and information leak.
>
> Signed-off-by: Kangjie Lu <[email protected]>
> ---
> drivers/gpu/drm/gma500/cdv_intel_display.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/gpu/drm/gma500/cdv_intel_display.c b/drivers/gpu/drm/gma500/cdv_intel_display.c
> index f56852a503e8..8b784947ed3b 100644
> --- a/drivers/gpu/drm/gma500/cdv_intel_display.c
> +++ b/drivers/gpu/drm/gma500/cdv_intel_display.c
> @@ -405,6 +405,8 @@ static bool cdv_intel_find_dp_pll(const struct gma_limit_t *limit,
> struct gma_crtc *gma_crtc = to_gma_crtc(crtc);
> struct gma_clock_t clock;
>
> + memset(&clock, 0, sizeof(clock));

I guess whatever analyzer you use for this doesn't see past the ->clock
vfunc call, so shouldn't be a real issue. Also, it's not an information
disclosure since we only ever leak this to other kernel code, never
userspace.

But I guess doesn't hurt, so applied.
-Daniel

> +
> switch (refclk) {
> case 27000:
> if (target < 200000) {
> --
> 2.17.1
>

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