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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 7C348C43603 for ; Thu, 12 Dec 2019 13:02:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4B4922077B for ; Thu, 12 Dec 2019 13:02:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="g1naCWSf" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729181AbfLLNCt (ORCPT ); Thu, 12 Dec 2019 08:02:49 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:34766 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729170AbfLLNCt (ORCPT ); Thu, 12 Dec 2019 08:02:49 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=3pJOGHohHWFavJROLCsvbbpIq2FFgge+nGlDVwdmal0=; b=g1naCWSfvuTUKXR8v95IIZSG1 BlGiIpPknxTsRMpSnCiEmUjjYbYY9FzjMw/OXZ5oo7g14CsZKSLziBJD95QuLvreen+22baOXRWXm 4+H9kwGV+yaNfcyLubptMXgAEZSmeMrgUylH52O1P7GVPoE6S/T6zj/Fc1QE4QqNm/rFlBt9hxJxS WXTX6ouKpkeSk0DpHZa4CCx1pIP/pJ+cqRFmVe/S6P7brDPVwRPn2nHMFc0g14jBdqJ/0g0kzcgQf LhN7COXuxzUq2rjj7s7cC1XXLGzRTUD92p3E73Q7hZNU9Xh6r481ElB36bTiT55gJ/sbLRbTOEM96 TkWhRYC+Q==; Received: from hch by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1ifO7E-0006SH-3X; Thu, 12 Dec 2019 13:02:48 +0000 Date: Thu, 12 Dec 2019 05:02:48 -0800 From: Christoph Hellwig To: Haren Myneni Cc: mpe@ellerman.id.au, devicetree@vger.kernel.org, mikey@neuling.org, herbert@gondor.apana.org.au, npiggin@gmail.com, hch@infradead.org, sukadev@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH V2 07/13] powerpc/vas: Take reference to PID and mm for user space windows Message-ID: <20191212130248.GE3381@infradead.org> References: <1575861522.16318.9.camel@hbabu-laptop> <1575862366.16318.24.camel@hbabu-laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1575862366.16318.24.camel@hbabu-laptop> User-Agent: Mutt/1.12.1 (2019-06-15) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: devicetree-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org > + if (txwin->user_win) { > + /* > + * Window opened by child thread may not be closed when > + * it exits. So take reference to its pid and release it > + * when the window is free by parent thread. > + * Acquire a reference to the task's pid to make sure > + * pid will not be re-used. > + */ > + txwin->pid = get_task_pid(current, PIDTYPE_PID); > + /* > + * Acquire a reference to the task's mm. > + */ > + txwin->mm = get_task_mm(current); > + > + if (txwin->mm) { > + mmput(txwin->mm); > + mmgrab(txwin->mm); Doesn't the mmgrab need to come before the mmput? > + mm_context_add_copro(txwin->mm); > + } else { > + put_pid(txwin->pid); > + pr_err("VAS: pid(%d): mm_struct is not found\n", > + current->pid); > + rc = -EPERM; > + goto free_window; > + } Also the code is much easier to follow if you handle the error first and avoid the else: txwin->mm = get_task_mm(current); if (!txwin->mm) { put_pid(txwin->pid); pr_err("VAS: pid(%d): mm_struct is not found\n", current->pid); rc = -EPERM; goto free_window; } mmgrab(txwin->mm); mmput(txwin->mm); Also don't you need to take a reference to the struct pid for the tgid as well?