linux-kernel - [PATCH 1/1] drm: avoid exposing kernel stack in compat_drm

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Message-Id: <1471802179-2886-1-git-send-email-xypron.glpk@gmx.de>
Date:   Sun, 21 Aug 2016 19:56:19 +0200
From:   Heinrich Schuchardt <xypron.glpk@....de>
To:     David Airlie <airlied@...ux.ie>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Heinrich Schuchardt <xypron.glpk@....de>
Subject: [PATCH 1/1] 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@....de>
---
 drivers/gpu/drm/drm_ioc32.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/drm_ioc32.c b/drivers/gpu/drm/drm_ioc32.c
index 57676f8..32a489b 100644
--- 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;
-- 
2.1.4