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=-14.4 required=3.0 tests=DKIMWL_WL_MED,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_IN_DEF_DKIM_WL 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 72D86C5ACD6 for ; Tue, 17 Mar 2020 18:41:28 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 3B98A20714 for ; Tue, 17 Mar 2020 18:41:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="s8za3E5G" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3B98A20714 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id E1AAA6B0006; Tue, 17 Mar 2020 14:41:27 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id DCB9F6B0007; Tue, 17 Mar 2020 14:41:27 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id CE1806B0008; Tue, 17 Mar 2020 14:41:27 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0207.hostedemail.com [216.40.44.207]) by kanga.kvack.org (Postfix) with ESMTP id B737D6B0006 for ; Tue, 17 Mar 2020 14:41:27 -0400 (EDT) Received: from smtpin02.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 931EB8245571 for ; Tue, 17 Mar 2020 18:41:27 +0000 (UTC) X-FDA: 76605722214.02.value86_46e0f62d72e22 X-HE-Tag: value86_46e0f62d72e22 X-Filterd-Recvd-Size: 4888 Received: from mail-ot1-f66.google.com (mail-ot1-f66.google.com [209.85.210.66]) by imf31.hostedemail.com (Postfix) with ESMTP for ; Tue, 17 Mar 2020 18:41:26 +0000 (UTC) Received: by mail-ot1-f66.google.com with SMTP id t28so20144369ott.5 for ; Tue, 17 Mar 2020 11:41:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=zqeTFrmm9hzoE8Ei7WXbY06jiJr+QU1mv/oiGm2r+iM=; b=s8za3E5GTL9xqEXCX6qpYZH20rsTRqMRJMoDP57Np3i5aoMg7NmPNGi9OQJ31a+O1e ziJ0svX/fqjjMPO8l8ofDVWDIYWOcNjCgucPRt53rsPsckFoQTGGnCLVw9jbj5KLoEs1 cQ35HZ3FpGvao4ZPHHf1vAyc/ZMifpSBYFYsdMQO7yCRtI2aP2Ix7yiQbfap8Vy7jccT /bkNk80SxHFtXACSsBkIghYfBUd1jfYAq6Fy+awf5L9+XjOkEKTCdk1BwDXF9VAj7Cv4 PHOJqaBtr/F/FHJPl5r4YmD+rK/y4FN+u9PW0NCWUq9WqZ2iCthkMLHUL2rkzt+4YAnh cw3Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=zqeTFrmm9hzoE8Ei7WXbY06jiJr+QU1mv/oiGm2r+iM=; b=Y38u68MoYu5SbbFczXgSdcrQOW/oP/B52FnlzL6UGzLGKwNekYMnC698ApSJQnlAiB vDJ1U8L7gYlBmsEvsBxIECY3RDnI98xU3eIfjgmymiLV6j8i4CKIi2kiDVPywByvkVv4 WKgkSh/TfrKTT2OOBBmDk/E1rr37AGmzxa5uFKO8V/OyQY4bBEHjtL8CPD/ee/C51cen TNRTy23U/V4cX3QdazjktTGQOQ8DKjQsBw+U00L3AFQpZ1KhjZR9TkNCqpmryuddt3Xk FWCe2CFHQzHuc4wgsiLfKICj+tHxVg6cHQqQJuKORgla9FWYPcD08T6m3OJhJes8GRoW EcAw== X-Gm-Message-State: ANhLgQ30yY4zdysVU1UKinEt1Q6BN3NSqwUAksgowUn8qpkGjVmnbp2w n0dGBGrc4Wt4bxSdYM0cV65idUDUObxgaXGJsuTNKA== X-Google-Smtp-Source: ADFU+vszSA1o2pLvYq/qAGXkejNLNYNwz+wQgc4J+iZlYicvbNaHvb+fJa86UFSBzrGtE96xtl6uovy7A2xL2/8WhFA= X-Received: by 2002:a05:6830:18d4:: with SMTP id v20mr598129ote.23.1584470485004; Tue, 17 Mar 2020 11:41:25 -0700 (PDT) MIME-Version: 1.0 References: <20200317182754.2180-1-cai@lca.pw> In-Reply-To: <20200317182754.2180-1-cai@lca.pw> From: Marco Elver Date: Tue, 17 Mar 2020 19:41:13 +0100 Message-ID: Subject: Re: [PATCH] mm/kmemleak: silence KCSAN splats in checksum To: Qian Cai Cc: Andrew Morton , catalin.marinas@arm.com, Linux Memory Management List , LKML Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, 17 Mar 2020 at 19:28, Qian Cai wrote: > > Even if KCSAN is disabled for kmemleak, update_checksum() could still > call crc32() (which is outside of kmemleak.c) to dereference > object->pointer. Thus, the value of object->pointer could be accessed > concurrently as noticed by KCSAN, > > BUG: KCSAN: data-race in crc32_le_base / do_raw_spin_lock > > write to 0xffffb0ea683a7d50 of 4 bytes by task 23575 on cpu 12: > do_raw_spin_lock+0x114/0x200 > debug_spin_lock_after at kernel/locking/spinlock_debug.c:91 > (inlined by) do_raw_spin_lock at kernel/locking/spinlock_debug.c:115 > _raw_spin_lock+0x40/0x50 > __handle_mm_fault+0xa9e/0xd00 > handle_mm_fault+0xfc/0x2f0 > do_page_fault+0x263/0x6f9 > page_fault+0x34/0x40 > > read to 0xffffb0ea683a7d50 of 4 bytes by task 839 on cpu 60: > crc32_le_base+0x67/0x350 > crc32_le_base+0x67/0x350: > crc32_body at lib/crc32.c:106 > (inlined by) crc32_le_generic at lib/crc32.c:179 > (inlined by) crc32_le at lib/crc32.c:197 > kmemleak_scan+0x528/0xd90 > update_checksum at mm/kmemleak.c:1172 > (inlined by) kmemleak_scan at mm/kmemleak.c:1497 > kmemleak_scan_thread+0xcc/0xfa > kthread+0x1e0/0x200 > ret_from_fork+0x27/0x50 > > If a shattered value was returned due to a data race, it will be > corrected in the next scan. Thus, let KCSAN ignore all reads in the > region to silence KCSAN in case the write side is non-atomic. > > Suggested-by: Marco Elver > Signed-off-by: Qian Cai Acked-by: Marco Elver Thanks, -- Marco > --- > mm/kmemleak.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/mm/kmemleak.c b/mm/kmemleak.c > index e362dc3d2028..5e252d91eb14 100644 > --- a/mm/kmemleak.c > +++ b/mm/kmemleak.c > @@ -1169,8 +1169,10 @@ static bool update_checksum(struct kmemleak_object *object) > u32 old_csum = object->checksum; > > kasan_disable_current(); > + kcsan_disable_current(); > object->checksum = crc32(0, (void *)object->pointer, object->size); > kasan_enable_current(); > + kcsan_enable_current(); > > return object->checksum != old_csum; > } > -- > 2.21.0 (Apple Git-122.2) >