linux-kernel - [PATCH AUTOSEL 5.4 052/108] fbdev: potential information leak in do_fb

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Message-Id: <20200411230943.24951-52-sashal@kernel.org>
Date:   Sat, 11 Apr 2020 19:08:47 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     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>,
        Sasha Levin <sashal@...nel.org>,
        dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org
Subject: [PATCH AUTOSEL 5.4 052/108] fbdev: potential information leak in do_fb_ioctl()

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

[ Upstream commit d3d19d6fc5736a798b118971935ce274f7deaa82 ]

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: Sasha Levin <sashal@...nel.org>
---
 drivers/video/fbdev/core/fbmem.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
index e6a1c805064f0..36469943795a8 100644
--- a/drivers/video/fbdev/core/fbmem.c
+++ b/drivers/video/fbdev/core/fbmem.c
@@ -1110,7 +1110,7 @@ static long do_fb_ioctl(struct fb_info *info, unsigned int cmd,
 		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);
-- 
2.20.1