From e0d4246a9441204e5ff5b6de69d72443b80de485 Mon Sep 17 00:00:00 2001
From: Julius Werner <jwerner@chromium.org>
Date: Fri, 2 Jun 2017 15:36:39 -0700
Subject: [PATCH] drivers: char: mem: Fix wraparound check to allow mappings up
 to the end

commit 32829da54d9368103a2f03269a5120aa9ee4d5da upstream.

A recent fix to /dev/mem prevents mappings from wrapping around the end
of physical address space. However, the check was written in a way that
also prevents a mapping reaching just up to the end of physical address
space, which may be a valid use case (especially on 32-bit systems).
This patch fixes it by checking the last mapped address (instead of the
first address behind that) for overflow.

Fixes: b299cde245 ("drivers: char: mem: Check for address space wraparound with mmap()")
Reported-by: Nico Huber <nico.h@gmx.de>
Signed-off-by: Julius Werner <jwerner@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
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