[PATCH AUTOSEL 5.5 060/121] fbdev: potential information leak in do_fb_ioctl()

[Sasha Levin]

From: Dan Carpenter <dan.carpenter@xxxxxxxxxx>

[ 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@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Cc: Andrea Righi <righi.andrea@xxxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: Sam Ravnborg <sam@xxxxxxxxxxxx>
Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
Cc: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
Cc: Peter Rosin <peda@xxxxxxxxxx>
Cc: Jani Nikula <jani.nikula@xxxxxxxxx>
Cc: Gerd Hoffmann <kraxel@xxxxxxxxxx>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@xxxxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20200113100132.ixpaymordi24n3av@xxxxxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 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 6f6fc785b5453..28158e21672ad 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