From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 79546C433F5 for ; Sun, 6 Mar 2022 09:37:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233200AbiCFJib (ORCPT ); Sun, 6 Mar 2022 04:38:31 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43586 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233222AbiCFJia (ORCPT ); Sun, 6 Mar 2022 04:38:30 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 85CDE1D0C8 for ; Sun, 6 Mar 2022 01:37:35 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id F0442B80E69 for ; Sun, 6 Mar 2022 09:37:33 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 431F6C340EE; Sun, 6 Mar 2022 09:37:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1646559452; bh=98I+jKwjc6w7SgbG68FnprP9Lne95WetTHqTbR9SnuQ=; h=Subject:To:Cc:From:Date:From; b=TiKpfhUjNNkh4J3e2fCpK75LlmnyVPEPRpUpvqg1/1t23vFSG0WbBnK4QNz3bwdqE Ck/BsqUajKzxS/hCPnHX7FCBhndrKPomSoNasUbsffkK+Vgka2EXn5cLo5XBQf+9LD Fctw1CGeC/HKvZmJrtlWjmwlMFVv7akcbURyXpd4= Subject: FAILED: patch "[PATCH] mm: prevent vm_area_struct::anon_name refcount saturation" failed to apply to 5.15-stable tree To: surenb@google.com, akpm@linux-foundation.org, brauner@kernel.org, caoxiaofeng@yulong.com, ccross@google.com, chris.hyser@oracle.com, dave.hansen@intel.com, dave@stgolabs.net, david@redhat.com, ebiederm@xmission.com, gorcunov@gmail.com, hannes@cmpxchg.org, keescook@chromium.org, kirill.shutemov@linux.intel.com, legion@kernel.org, mhocko@suse.com, pcc@google.com, sashal@kernel.org, sumit.semwal@linaro.org, torvalds@linux-foundation.org, vbabka@suse.cz, willy@infradead.org Cc: From: Date: Sun, 06 Mar 2022 10:37:21 +0100 Message-ID: <1646559441105125@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 96403e11283def1d1c465c8279514c9a504d8630 Mon Sep 17 00:00:00 2001 From: Suren Baghdasaryan Date: Fri, 4 Mar 2022 20:28:55 -0800 Subject: [PATCH] mm: prevent vm_area_struct::anon_name refcount saturation A deep process chain with many vmas could grow really high. With default sysctl_max_map_count (64k) and default pid_max (32k) the max number of vmas in the system is 2147450880 and the refcounter has headroom of 1073774592 before it reaches REFCOUNT_SATURATED (3221225472). Therefore it's unlikely that an anonymous name refcounter will overflow with these defaults. Currently the max for pid_max is PID_MAX_LIMIT (4194304) and for sysctl_max_map_count it's INT_MAX (2147483647). In this configuration anon_vma_name refcount overflow becomes theoretically possible (that still require heavy sharing of that anon_vma_name between processes). kref refcounting interface used in anon_vma_name structure will detect a counter overflow when it reaches REFCOUNT_SATURATED value but will only generate a warning and freeze the ref counter. This would lead to the refcounted object never being freed. A determined attacker could leak memory like that but it would be rather expensive and inefficient way to do so. To ensure anon_vma_name refcount does not overflow, stop anon_vma_name sharing when the refcount reaches REFCOUNT_MAX (2147483647), which still leaves INT_MAX/2 (1073741823) values before the counter reaches REFCOUNT_SATURATED. This should provide enough headroom for raising the refcounts temporarily. Link: https://lkml.kernel.org/r/20220223153613.835563-2-surenb@google.com Signed-off-by: Suren Baghdasaryan Suggested-by: Michal Hocko Acked-by: Michal Hocko Cc: Alexey Gladkov Cc: Chris Hyser Cc: Christian Brauner Cc: Colin Cross Cc: Cyrill Gorcunov Cc: Dave Hansen Cc: David Hildenbrand Cc: Davidlohr Bueso Cc: "Eric W. Biederman" Cc: Johannes Weiner Cc: Kees Cook Cc: "Kirill A. Shutemov" Cc: Matthew Wilcox Cc: Peter Collingbourne Cc: Sasha Levin Cc: Sumit Semwal Cc: Vlastimil Babka Cc: Xiaofeng Cao Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h index dd3accaa4e6d..cf90b1fa2c60 100644 --- a/include/linux/mm_inline.h +++ b/include/linux/mm_inline.h @@ -161,15 +161,25 @@ static inline void anon_vma_name_put(struct anon_vma_name *anon_name) kref_put(&anon_name->kref, anon_vma_name_free); } +static inline +struct anon_vma_name *anon_vma_name_reuse(struct anon_vma_name *anon_name) +{ + /* Prevent anon_name refcount saturation early on */ + if (kref_read(&anon_name->kref) < REFCOUNT_MAX) { + anon_vma_name_get(anon_name); + return anon_name; + + } + return anon_vma_name_alloc(anon_name->name); +} + static inline void dup_anon_vma_name(struct vm_area_struct *orig_vma, struct vm_area_struct *new_vma) { struct anon_vma_name *anon_name = anon_vma_name(orig_vma); - if (anon_name) { - anon_vma_name_get(anon_name); - new_vma->anon_name = anon_name; - } + if (anon_name) + new_vma->anon_name = anon_vma_name_reuse(anon_name); } static inline void free_anon_vma_name(struct vm_area_struct *vma) diff --git a/mm/madvise.c b/mm/madvise.c index 081b1cded21e..1f2693dccf7b 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -113,8 +113,7 @@ static int replace_anon_vma_name(struct vm_area_struct *vma, if (anon_vma_name_eq(orig_name, anon_name)) return 0; - anon_vma_name_get(anon_name); - vma->anon_name = anon_name; + vma->anon_name = anon_vma_name_reuse(anon_name); anon_vma_name_put(orig_name); return 0;