From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from out1-smtp.messagingengine.com ([66.111.4.25]:33253 "EHLO out1-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752560AbdGCLqK (ORCPT ); Mon, 3 Jul 2017 07:46:10 -0400 Date: Mon, 3 Jul 2017 13:46:10 +0200 From: Greg KH To: Ard Biesheuvel Cc: stable@vger.kernel.org, akpm@linux-foundation.org, broonie@kernel.org, mark.rutland@arm.com, labbott@redhat.com, Michal Hocko , zhong jiang , Dave Hansen , Linus Torvalds Subject: Re: [STABLE BACKPORT] mm/vmalloc.c: huge-vmap: fail gracefully on unexpected huge vmap mappings Message-ID: <20170703114610.GA19948@kroah.com> References: <20170703111351.26561-1-ard.biesheuvel@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170703111351.26561-1-ard.biesheuvel@linaro.org> Sender: stable-owner@vger.kernel.org List-ID: On Mon, Jul 03, 2017 at 12:13:51PM +0100, Ard Biesheuvel wrote: > Existing code that uses vmalloc_to_page() may assume that any address > for which is_vmalloc_addr() returns true may be passed into > vmalloc_to_page() to retrieve the associated struct page. > > This is not un unreasonable assumption to make, but on architectures > that have CONFIG_HAVE_ARCH_HUGE_VMAP=y, it no longer holds, and we need > to ensure that vmalloc_to_page() does not go off into the weeds trying > to dereference huge PUDs or PMDs as table entries. > > Given that vmalloc() and vmap() themselves never create huge mappings or > deal with compound pages at all, there is no correct answer in this > case, so return NULL instead, and issue a warning. > > When reading /proc/kcore on arm64, you will hit an oops as soon as you > hit the huge mappings used for the various segments that make up the > mapping of vmlinux. With this patch applied, you will no longer hit the > oops, but the kcore contents willl be incorrect (these regions will be > zeroed out) > > We are fixing this for kcore specifically, so it avoids vread() for > those regions. At least one other problematic user exists, i.e., > /dev/kmem, but that is currently broken on arm64 for other reasons. > > Link: http://lkml.kernel.org/r/20170609082226.26152-1-ard.biesheuvel@linaro.org > Signed-off-by: Ard Biesheuvel > Acked-by: Mark Rutland > Reviewed-by: Laura Abbott > Cc: Michal Hocko > Cc: zhong jiang > Cc: Dave Hansen > Signed-off-by: Andrew Morton > Signed-off-by: Linus Torvalds > (cherry picked from commit 029c54b09599573015a5c18dbe59cbdf42742237) > [ardb: non-trivial backport to v4.9] Thanks for this, now queued up. greg k-h