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=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 CC785C54FC9 for ; Tue, 21 Apr 2020 19:33:51 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 8E733206D5 for ; Tue, 21 Apr 2020 19:33:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8E733206D5 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=zeniv.linux.org.uk Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 496DJZ0DQmzDr09 for ; Wed, 22 Apr 2020 05:33:50 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=none (no SPF record) smtp.mailfrom=ftp.linux.org.uk (client-ip=2002:c35c:fd02::1; helo=zeniv.linux.org.uk; envelope-from=viro@ftp.linux.org.uk; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=zeniv.linux.org.uk Received: from ZenIV.linux.org.uk (zeniv.linux.org.uk [IPv6:2002:c35c:fd02::1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 496D7S00kszDqY6 for ; Wed, 22 Apr 2020 05:25:55 +1000 (AEST) Received: from viro by ZenIV.linux.org.uk with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jQyWW-007mYP-P6; Tue, 21 Apr 2020 19:25:36 +0000 Date: Tue, 21 Apr 2020 20:25:36 +0100 From: Al Viro To: Christoph Hellwig Subject: Re: [PATCH 1/7] powerpc/spufs: simplify spufs core dumping Message-ID: <20200421192536.GG23230@ZenIV.linux.org.uk> References: <20200421154204.252921-1-hch@lst.de> <20200421154204.252921-2-hch@lst.de> <20200421184941.GD23230@ZenIV.linux.org.uk> <20200421190148.GA26071@lst.de> <20200421191909.GF23230@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200421191909.GF23230@ZenIV.linux.org.uk> X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Arnd Bergmann , linux-kernel@vger.kernel.org, Jeremy Kerr , linux-fsdevel@vger.kernel.org, Andrew Morton , linuxppc-dev@lists.ozlabs.org, "Eric W . Biederman" Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Tue, Apr 21, 2020 at 08:19:09PM +0100, Al Viro wrote: > On Tue, Apr 21, 2020 at 09:01:48PM +0200, Christoph Hellwig wrote: > > On Tue, Apr 21, 2020 at 07:49:41PM +0100, Al Viro wrote: > > > > spin_lock(&ctx->csa.register_lock); > > > > - ret = __spufs_proxydma_info_read(ctx, buf, len, pos); > > > > + __spufs_proxydma_info_read(ctx, &info); > > > > + ret = simple_read_from_buffer(buf, len, pos, &info, sizeof(info)); > > > > > > IDGI... What's that access_ok() for? If you are using simple_read_from_buffer(), > > > the damn thing goes through copy_to_user(). Why bother with separate access_ok() > > > here? > > > > I have no idea at all, this just refactors the code. > > Wait a bloody minute, it's doing *what* under a spinlock? ... and yes, I realize that it's been broken the same way. It still needs fixing. AFAICS, that got broken in commit bf1ab978be23 "[POWERPC] coredump: Add SPU elf notes to coredump." when spufs_proxydma_info_read() had copy_to_user() (until then done after dropping the spinlock) moved into an area where blocking is very much *not* allowed.