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=-0.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=no 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 3B98BC35280 for ; Fri, 8 May 2020 00:02:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 068E9208E4 for ; Fri, 8 May 2020 00:02:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588896165; bh=RABDbBls9l0rquFOQ6ZOjxQs3c2PLTi1b71bICyJ9LY=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=Ny5k3Ry3BhGfyWGK7F4KSRjRk4IpPqS+fO5KzDbUgQBSLTVDpciDQvFqBVmFLPDl1 E6awfs2o8NlYIKavan5o3o1Mkb6anY3+r2ZXYrJE12aQEh7eIOt+79oR0ttQ/3LkCU aKInibbHFgLpimMaEimziLj1uNG2DtE6VrlUasIM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726618AbgEHACo (ORCPT ); Thu, 7 May 2020 20:02:44 -0400 Received: from mail.kernel.org ([198.145.29.99]:55964 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726464AbgEHACn (ORCPT ); Thu, 7 May 2020 20:02:43 -0400 Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id E4F4B2082E; Fri, 8 May 2020 00:02:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588896163; bh=RABDbBls9l0rquFOQ6ZOjxQs3c2PLTi1b71bICyJ9LY=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=0MFQAWy486qPwRfsFfPZP/Ol8J7LIIJNa0Sdix9A/QkaXqiBndS/dnAOkDzv4KLff KGEMLEkJqZ4OxRgB20i2VL+At0WSFKX5o21m8dPBD5HHhiG18dHlZonMQf0MiEFAp6 rkj74qkGEu4pT3hjd/RdJk51LbH72np8MrGqoM+g= Date: Thu, 7 May 2020 17:02:42 -0700 From: Andrew Morton To: Vasily Averin Cc: linux-kernel@vger.kernel.org, Waiman Long , Andreas Schwab , Matthew Wilcox Subject: Re: [PATCH] ipc/util.c: sysvipc_find_ipc() incorrectly updates position index Message-Id: <20200507170242.6cbb88ae672deed67152e221@linux-foundation.org> In-Reply-To: <4921fe9b-9385-a2b4-1dc4-1099be6d2e39@virtuozzo.com> References: <4921fe9b-9385-a2b4-1dc4-1099be6d2e39@virtuozzo.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 6 May 2020 09:25:54 +0300 Vasily Averin wrote: > new_pos should jump through hole of unused ids, > pos can be updated inside "for" cycle. > > Cc: stable@vger.kernel.org > Fixes: 89163f93c6f9 ("ipc/util.c: sysvipc_find_ipc() should increase position index") This: > --- a/ipc/util.c > +++ b/ipc/util.c > @@ -764,21 +764,21 @@ static struct kern_ipc_perm *sysvipc_find_ipc(struct ipc_ids *ids, loff_t pos, > total++; > } > > - *new_pos = pos + 1; > + ipc = NULL; > if (total >= ids->in_use) > - return NULL; > + goto out; > > for (; pos < ipc_mni; pos++) { > ipc = idr_find(&ids->ipcs_idr, pos); > if (ipc != NULL) { > rcu_read_lock(); > ipc_lock_object(ipc); > - return ipc; > + break; > } > } > - > - /* Out of range - return NULL to terminate iteration */ > - return NULL; > +out: > + *new_pos = pos + 1; > + return ipc; > } > > static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos) Messes up Matthew's "ipc: convert ipcs_idr to XArray" (http://lkml.kernel.org/r/20200326151418.27545-1-willy@infradead.org). Here's how I resolved things. Please check? static struct kern_ipc_perm *sysvipc_find_ipc(struct ipc_ids *ids, loff_t pos, loff_t *new_pos) { unsigned long index = pos; struct kern_ipc_perm *ipc; rcu_read_lock(); ipc = xa_find(&ids->ipcs, &index, ULONG_MAX, XA_PRESENT); if (ipc) ipc_lock_object(ipc); else rcu_read_unlock(); *new_pos = pos + 1; return ipc; }