drm: avoid exposing kernel stack in compat_drm_getstats

The C standard does not specify the size of the integer used
to store an enum. Hence in structure drm_stats32_t alignment
bytes may exist.

To avoid exposing bytes from the kernel stack it is
necessary to initialize variable s32 completely.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1471802179-2886-1-git-send-email-xypron.glpk@gmx.de

diff --git a/drivers/gpu/drm/drm_ioc32.c b/drivers/gpu/drm/drm_ioc32.c
index 57676f8..32a489b 100644 (file)
--- a/drivers/gpu/drm/drm_ioc32.c
+++ b/drivers/gpu/drm/drm_ioc32.c
@@ -346,6 +346,7 @@ static int compat_drm_getstats(struct file *file, unsigned int cmd,
        struct drm_stats __user *stats;
        int i, err;
 
+       memset(&s32, 0, sizeof(drm_stats32_t));
        stats = compat_alloc_user_space(sizeof(*stats));
        if (!stats)
                return -EFAULT;