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 X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4D41FC3B1BF for ; Fri, 14 Feb 2020 20:33:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 166C624649 for ; Fri, 14 Feb 2020 20:33:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lca.pw header.i=@lca.pw header.b="sjIUvkrE" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730220AbgBNUdl (ORCPT ); Fri, 14 Feb 2020 15:33:41 -0500 Received: from mail-qt1-f193.google.com ([209.85.160.193]:43562 "EHLO mail-qt1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730005AbgBNUdl (ORCPT ); Fri, 14 Feb 2020 15:33:41 -0500 Received: by mail-qt1-f193.google.com with SMTP id d18so7853520qtj.10 for ; Fri, 14 Feb 2020 12:33:39 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=lca.pw; s=google; h=from:to:cc:subject:date:message-id; bh=utuuKup5LPG796OspCxT2KOedNLQisnMmifEVidt+tA=; b=sjIUvkrE9OQgMUIDitVEp37YqU2yJhK8JAzMi9of98q4BS8b5IUla33MvC49S7FPQn eMu+4QizwQK4DKvwM2ByOMRATGQv9tjlG4ChxzZdwKKqQ9KTiQDfgm92d9q3zNyKPZ/K O/FAde970kkXvyahHPJMZKw5aKBX9YwQSulTCD6kL7zwk+YULf+VbhYpFtlz4J7rNRWY pGu8Mh5fxhdJSaSA78adT8bLU2DOnpVoVTW+IRmT53h/elKdizX7INy4xdv69FE38EK0 Wv4U8hhh31hiswvLH5EMHRjWaThyar9rTZ2zmea4QYNP1TLnqivImZnS+Ph105rqXY/b vpOA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id; bh=utuuKup5LPG796OspCxT2KOedNLQisnMmifEVidt+tA=; b=nDAl1G1xRlXePqW++7TpqzQe2mlBX/NvlycvayO0YXn+S+DqQwnf9gtOsbKpM92BMu 9Kl/jOqqztAq2JR9N575ACbAnDL1IdTxM+j3Am+U0zH0OZG87cmzkbReE6G0wYwQmoUq vf7sOGkx5p4fPwFXuOrhNjuoADf4r0HfsQTVmWMzs02H24YYqpNBSQhUCaKLsDARkJiG fLo/uBahcZstBU3Q8i//hq2virV81eHcGLmSWeaScJMCrRVsD2UBHLKgqEf3NNOpT/kk +8SZ8mkaquqCfaqAmFuBgLK9lpjUEKe9IpL0vGoh356Ze5Ld7NHCCipMU7/HICYpFiWp syKQ== X-Gm-Message-State: APjAAAWW1wZSuJ12tjVQlc7faD67tH/SYQHWUB2XwpKuQiE+L5bdBITk gXO75fIXaxSn4vqj9wq/5EWC8w== X-Google-Smtp-Source: APXvYqzp0yEutPBy8OYKLKKPHZiW/W3QbOXwwJbuUuTg+0yaqq+Km4hVxuoJ2ybYHCYhE2i+2V0wQQ== X-Received: by 2002:ac8:7392:: with SMTP id t18mr3874950qtp.332.1581712418467; Fri, 14 Feb 2020 12:33:38 -0800 (PST) Received: from qcai.nay.com (nat-pool-bos-t.redhat.com. [66.187.233.206]) by smtp.gmail.com with ESMTPSA id l184sm3926233qkc.107.2020.02.14.12.33.37 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 14 Feb 2020 12:33:37 -0800 (PST) From: Qian Cai To: akpm@linux-foundation.org Cc: elver@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Qian Cai Subject: [PATCH -next] fork: annotate a data race in vm_area_dup() Date: Fri, 14 Feb 2020 15:33:23 -0500 Message-Id: <1581712403-27243-1-git-send-email-cai@lca.pw> X-Mailer: git-send-email 1.8.3.1 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org struct vm_area_struct could be accessed concurrently as noticed by KCSAN, write to 0xffff9cf8bba08ad8 of 8 bytes by task 14263 on cpu 35: vma_interval_tree_insert+0x101/0x150: rb_insert_augmented_cached at include/linux/rbtree_augmented.h:58 (inlined by) vma_interval_tree_insert at mm/interval_tree.c:23 __vma_link_file+0x6e/0xe0 __vma_link_file at mm/mmap.c:629 vma_link+0xa2/0x120 mmap_region+0x753/0xb90 do_mmap+0x45c/0x710 vm_mmap_pgoff+0xc0/0x130 ksys_mmap_pgoff+0x1d1/0x300 __x64_sys_mmap+0x33/0x40 do_syscall_64+0x91/0xc44 entry_SYSCALL_64_after_hwframe+0x49/0xbe read to 0xffff9cf8bba08a80 of 200 bytes by task 14262 on cpu 122: vm_area_dup+0x6a/0xe0 vm_area_dup at kernel/fork.c:362 __split_vma+0x72/0x2a0 __split_vma at mm/mmap.c:2661 split_vma+0x5a/0x80 mprotect_fixup+0x368/0x3f0 do_mprotect_pkey+0x263/0x420 __x64_sys_mprotect+0x51/0x70 do_syscall_64+0x91/0xc44 entry_SYSCALL_64_after_hwframe+0x49/0xbe The write is holding mmap_sem while changing vm_area_struct.shared.rb. Even though the read is lockless while making a copy, the clone will have its own shared.rb reinitialized. Thus, mark it as an intentional data race using the data_race() macro. Signed-off-by: Qian Cai --- kernel/fork.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/kernel/fork.c b/kernel/fork.c index 41f784b6203a..81bdc6e8a6cf 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -359,7 +359,11 @@ struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig) struct vm_area_struct *new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); if (new) { - *new = *orig; + /* + * @orig may be modified concurrently, but the clone will be + * reinitialized. + */ + *new = data_race(*orig); INIT_LIST_HEAD(&new->anon_vma_chain); } return new; -- 1.8.3.1