From patchwork Mon Oct 22 11:48:50 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jan Kara X-Patchwork-Id: 10651935 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 4CFD613A9 for ; Mon, 22 Oct 2018 11:49:09 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 3A2EA287DA for ; Mon, 22 Oct 2018 11:49:09 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 2E544287F8; Mon, 22 Oct 2018 11:49:09 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B554C287DA for ; Mon, 22 Oct 2018 11:49:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728273AbeJVUHS (ORCPT ); Mon, 22 Oct 2018 16:07:18 -0400 Received: from mx2.suse.de ([195.135.220.15]:60820 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728250AbeJVUHS (ORCPT ); Mon, 22 Oct 2018 16:07:18 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 88720AFA8; Mon, 22 Oct 2018 11:49:03 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 507281E044E; Mon, 22 Oct 2018 13:49:02 +0200 (CEST) From: Jan Kara To: Al Viro Cc: , Jan Kara , Theodore Ts'o , Miklos Szeredi Subject: [PATCH] vfs: Do not allow underflowing of i_nlink Date: Mon, 22 Oct 2018 13:48:50 +0200 Message-Id: <20181022114850.1912-1-jack@suse.cz> X-Mailer: git-send-email 2.16.4 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Currently, drop_nlink() warns when i_nlink underflows but it still lets the value underflow. Granted such underflow means filesystem corruption so we are screwed but still it limits the damage more if we leave i_nlink at 0 to keep inode in "unlinked" state instead of letting it magically appear linked again which confuses filesystems even more. For example this would make b50282f3241a "ext4: check to make sure the rename(2)'s destination is not freed" just a cosmetic fix instead of a memory-corruption fix. CC: Theodore Ts'o CC: Miklos Szeredi Signed-off-by: Jan Kara --- fs/inode.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/inode.c b/fs/inode.c index 42f6d25f32a5..d449824a90de 100644 --- a/fs/inode.c +++ b/fs/inode.c @@ -282,7 +282,8 @@ static void destroy_inode(struct inode *inode) */ void drop_nlink(struct inode *inode) { - WARN_ON(inode->i_nlink == 0); + if (WARN_ON(inode->i_nlink == 0)) + return; inode->__i_nlink--; if (!inode->i_nlink) atomic_long_inc(&inode->i_sb->s_remove_count);