fbdev: save the activate field before calling fb_check_var()

Some drivers may reset the var->activate field on fb_check_var(). This can
lead to undefined behavior. For example, doing fbset -a <option> with vga16fb
will only modify the active console instead of modifying all.

Signed-off-by: Antonino Daplas <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/video/fbmem.c

···
 
 	if ((var->activate & FB_ACTIVATE_FORCE) ||
 	    memcmp(&info->var, var, sizeof(struct fb_var_screeninfo))) {
+		u32 activate = var->activate;
+
 		if (!info->fbops->fb_check_var) {
 			*var = info->var;
 			return 0;
···
 
 			if (!err && (flags & FBINFO_MISC_USEREVENT)) {
 				struct fb_event event;
-				int evnt = (var->activate & FB_ACTIVATE_ALL) ?
+				int evnt = (activate & FB_ACTIVATE_ALL) ?
 					FB_EVENT_MODE_CHANGE_ALL :
 					FB_EVENT_MODE_CHANGE;