linux-kernel - [PATCH 5.6 150/166] fbdev: potential information leak in do_fb

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Date:   Wed, 22 Apr 2020 11:57:57 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dan Carpenter <dan.carpenter@...cle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Andrea Righi <righi.andrea@...il.com>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Sam Ravnborg <sam@...nborg.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Peter Rosin <peda@...ntia.se>,
        Jani Nikula <jani.nikula@...el.com>,
        Gerd Hoffmann <kraxel@...hat.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: [PATCH 5.6 150/166] fbdev: potential information leak in do_fb_ioctl()

From: Dan Carpenter <dan.carpenter@...cle.com>

commit d3d19d6fc5736a798b118971935ce274f7deaa82 upstream.

The "fix" struct has a 2 byte hole after ->ywrapstep and the
"fix = info->fix;" assignment doesn't necessarily clear it.  It depends
on the compiler.  The solution is just to replace the assignment with an
memcpy().

Fixes: 1f5e31d7e55a ("fbmem: don't call copy_from/to_user() with mutex held")
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: "Eric W. Biederman" <ebiederm@...ssion.com>
Cc: Andrea Righi <righi.andrea@...il.com>
Cc: Daniel Vetter <daniel.vetter@...ll.ch>
Cc: Sam Ravnborg <sam@...nborg.org>
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>
Cc: Daniel Thompson <daniel.thompson@...aro.org>
Cc: Peter Rosin <peda@...ntia.se>
Cc: Jani Nikula <jani.nikula@...el.com>
Cc: Gerd Hoffmann <kraxel@...hat.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200113100132.ixpaymordi24n3av@kili.mountain
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/video/fbdev/core/fbmem.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/video/fbdev/core/fbmem.c
+++ b/drivers/video/fbdev/core/fbmem.c
@@ -1115,7 +1115,7 @@ static long do_fb_ioctl(struct fb_info *
 		break;
 	case FBIOGET_FSCREENINFO:
 		lock_fb_info(info);
-		fix = info->fix;
+		memcpy(&fix, &info->fix, sizeof(fix));
 		if (info->flags & FBINFO_HIDE_SMEM_START)
 			fix.smem_start = 0;
 		unlock_fb_info(info);