From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f72.google.com (mail-oi0-f72.google.com [209.85.218.72]) by kanga.kvack.org (Postfix) with ESMTP id 7A27F6B0008 for ; Wed, 1 Aug 2018 16:04:24 -0400 (EDT) Received: by mail-oi0-f72.google.com with SMTP id 20-v6so17805764ois.21 for ; Wed, 01 Aug 2018 13:04:24 -0700 (PDT) Received: from foss.arm.com (foss.arm.com. [217.140.101.70]) by mx.google.com with ESMTP id e66-v6si11529738oif.85.2018.08.01.13.04.23 for ; Wed, 01 Aug 2018 13:04:23 -0700 (PDT) From: Jeremy Linton Subject: [RFC 2/2] mm: harden alloc_pages code paths against bogus nodes Date: Wed, 1 Aug 2018 15:04:18 -0500 Message-Id: <20180801200418.1325826-3-jeremy.linton@arm.com> In-Reply-To: <20180801200418.1325826-1-jeremy.linton@arm.com> References: <20180801200418.1325826-1-jeremy.linton@arm.com> Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org Cc: cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, mhocko@suse.com, vbabka@suse.cz, Punit.Agrawal@arm.com, Lorenzo.Pieralisi@arm.com, linux-arm-kernel@lists.infradead.org, bhelgaas@google.com, linux-kernel@vger.kernel.org, Jeremy Linton Its possible to crash __alloc_pages_nodemask by passing it bogus node ids. This is caused by NODE_DATA() returning null (hopefully) when the requested node is offline. We can harded against the basic case of a mostly valid node, that isn't online by checking for null and failing prepare_alloc_pages. But this then suggests we should also harden NODE_DATA() like this #define NODE_DATA(nid) ( (nid) < MAX_NUMNODES ? node_data[(nid)] : NULL) eventually this starts to add a bunch of generally uneeded checks in some code paths that are called quite frequently. Signed-off-by: Jeremy Linton --- include/linux/gfp.h | 2 ++ mm/page_alloc.c | 2 ++ 2 files changed, 4 insertions(+) diff --git a/include/linux/gfp.h b/include/linux/gfp.h index a6afcec53795..17d70271c42e 100644 --- a/include/linux/gfp.h +++ b/include/linux/gfp.h @@ -436,6 +436,8 @@ static inline int gfp_zonelist(gfp_t flags) */ static inline struct zonelist *node_zonelist(int nid, gfp_t flags) { + if (unlikely(!NODE_DATA(nid))) //VM_WARN_ON? + return NULL; return NODE_DATA(nid)->node_zonelists + gfp_zonelist(flags); } diff --git a/mm/page_alloc.c b/mm/page_alloc.c index a790ef4be74e..3a3d9ac2662a 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -4306,6 +4306,8 @@ static inline bool prepare_alloc_pages(gfp_t gfp_mask, unsigned int order, { ac->high_zoneidx = gfp_zone(gfp_mask); ac->zonelist = node_zonelist(preferred_nid, gfp_mask); + if (!ac->zonelist) + return false; ac->nodemask = nodemask; ac->migratetype = gfpflags_to_migratetype(gfp_mask); -- 2.14.3