drivers: char: mem: Check for address space wraparound with mmap()
authorJulius Werner <jwerner@chromium.org>
Fri, 12 May 2017 21:42:58 +0000 (14:42 -0700)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Thu, 18 May 2017 14:53:55 +0000 (16:53 +0200)
commitb299cde245b0b76c977f4291162cf668e087b408
treeec107352e8c72071d42d7627f8612c70f9d477f7
parent0d83539092ddb1ab79b4d65bccb866bf07ea2ccd
drivers: char: mem: Check for address space wraparound with mmap()

/dev/mem currently allows mmap() mappings that wrap around the end of
the physical address space, which should probably be illegal. It
circumvents the existing STRICT_DEVMEM permission check because the loop
immediately terminates (as the start address is already higher than the
end address). On the x86_64 architecture it will then cause a panic
(from the BUG(start >= end) in arch/x86/mm/pat.c:reserve_memtype()).

This patch adds an explicit check to make sure offset + size will not
wrap around in the physical address type.

Signed-off-by: Julius Werner <jwerner@chromium.org>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
drivers/char/mem.c