From patchwork Tue Apr 12 06:30:30 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 560730 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 3800BC433EF for ; Tue, 12 Apr 2022 06:48:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1349974AbiDLGuX (ORCPT ); Tue, 12 Apr 2022 02:50:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57840 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1349989AbiDLGsi (ORCPT ); Tue, 12 Apr 2022 02:48:38 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 43D8226131; Mon, 11 Apr 2022 23:39:26 -0700 (PDT) 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 C04C0B81B51; Tue, 12 Apr 2022 06:39:24 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3816CC385A6; Tue, 12 Apr 2022 06:39:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1649745563; bh=Z9j1K/1X50RjsQ38uUw45U8tNynepeVJoyteu79dlTk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=p4/+OBrxGpn0vF2j3Zu24i7MqvYjbyaGqvhFEta5j6FQDieZr1Am0jJdsuZGE7coV 20nxVQIbZRXV1nJ1SMvYwQ4lgjYO1LGqiefbCwe7u1FH0GAE93+2tCjS+vxMi5bB4G maoxFc/XbnXAPx7V/meDN6XLtRrypb/UL4Be89N4= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, syzbot+6bde52d89cfdf9f61425@syzkaller.appspotmail.com, Paolo Bonzini , Sean Christopherson , Andrew Morton , Linus Torvalds Subject: [PATCH 5.10 139/171] mmmremap.c: avoid pointless invalidate_range_start/end on mremap(old_size=0) Date: Tue, 12 Apr 2022 08:30:30 +0200 Message-Id: <20220412062931.910534268@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220412062927.870347203@linuxfoundation.org> References: <20220412062927.870347203@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Paolo Bonzini commit 01e67e04c28170c47700c2c226d732bbfedb1ad0 upstream. If an mremap() syscall with old_size=0 ends up in move_page_tables(), it will call invalidate_range_start()/invalidate_range_end() unnecessarily, i.e. with an empty range. This causes a WARN in KVM's mmu_notifier. In the past, empty ranges have been diagnosed to be off-by-one bugs, hence the WARNing. Given the low (so far) number of unique reports, the benefits of detecting more buggy callers seem to outweigh the cost of having to fix cases such as this one, where userspace is doing something silly. In this particular case, an early return from move_page_tables() is enough to fix the issue. Link: https://lkml.kernel.org/r/20220329173155.172439-1-pbonzini@redhat.com Reported-by: syzbot+6bde52d89cfdf9f61425@syzkaller.appspotmail.com Signed-off-by: Paolo Bonzini Cc: Sean Christopherson Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/mremap.c | 3 +++ 1 file changed, 3 insertions(+) --- a/mm/mremap.c +++ b/mm/mremap.c @@ -260,6 +260,9 @@ unsigned long move_page_tables(struct vm struct mmu_notifier_range range; pmd_t *old_pmd, *new_pmd; + if (!len) + return 0; + old_end = old_addr + len; flush_cache_range(vma, old_addr, old_end);