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 17BFFC433F5 for ; Sun, 10 Apr 2022 04:39:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231834AbiDJEl0 (ORCPT ); Sun, 10 Apr 2022 00:41:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46088 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231797AbiDJElV (ORCPT ); Sun, 10 Apr 2022 00:41:21 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C0FBD634E; Sat, 9 Apr 2022 21:39:09 -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 2169FB80B87; Sun, 10 Apr 2022 04:39:08 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id AAC07C385A5; Sun, 10 Apr 2022 04:39:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1649565546; bh=eXcEXo0mhuRisakInDEzdxM5D6U9aHrHR81T6Nsf8yk=; h=Date:To:From:Subject:From; b=BYwUGA9xFKu5a9M4t3gdBwtlfdxx2CBnTuuye7DNihdzmbkcrRdc+l35OqahvHi6b 6JcOvX6iK+upf8Z46vvEUBzCPQ+HnzfXETrzLa0W5EHT+fBhXHgF8zXVwLwE+YCQW7 NnMvXDrEYJz12oDnyUp7QWiGvGhW732IiLQ1uzZs= Date: Sat, 09 Apr 2022 21:39:06 -0700 To: mm-commits@vger.kernel.org, stable@vger.kernel.org, seanjc@google.com, pbonzini@redhat.com, akpm@linux-foundation.org From: Andrew Morton Subject: [merged] mm-avoid-pointless-invalidate_range_start-end-on-mremapold_size=0.patch removed from -mm tree Message-Id: <20220410043906.AAC07C385A5@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The patch titled Subject: mmmremap.c: avoid pointless invalidate_range_start/end on mremap(old_size=0) has been removed from the -mm tree. Its filename was mm-avoid-pointless-invalidate_range_start-end-on-mremapold_size=0.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: Paolo Bonzini Subject: mmmremap.c: avoid pointless invalidate_range_start/end on mremap(old_size=0) 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 --- mm/mremap.c | 3 +++ 1 file changed, 3 insertions(+) --- a/mm/mremap.c~mm-avoid-pointless-invalidate_range_start-end-on-mremapold_size=0 +++ a/mm/mremap.c @@ -486,6 +486,9 @@ unsigned long move_page_tables(struct vm pmd_t *old_pmd, *new_pmd; pud_t *old_pud, *new_pud; + if (!len) + return 0; + old_end = old_addr + len; flush_cache_range(vma, old_addr, old_end); _ Patches currently in -mm which might be from pbonzini@redhat.com are