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=-5.0 required=3.0 tests=BAYES_00,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 C1CA5C4363D for ; Wed, 23 Sep 2020 14:41:55 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (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 4C930206FB for ; Wed, 23 Sep 2020 14:41:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="dDmyzeps" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4C930206FB Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=zeniv.linux.org.uk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=n22quhTya1ffwvcLlxYGRfyWNJLaT5eZNOl7g45wDJg=; b=dDmyzepsNDvIrjZnsnHCLLDMm 5VtISs45Z2Gt5VqKDikNGSXV/Nz7wKauZ9XKjr1inX0YRxm6CcBHptGdGw/nry5b4x/54Gq3+lAZS WUFibzIAQQtitH5gi3nwmgvJJPcHLm17n++nqskKSHypJyrNkuOEzsCXzLYo/LpkTR2Ruoo1BCm/h 96FrCM0Wno/+Le2ww81IDiK0KqG9dWHRuX7GhMV9IBXkMOBdf8BSbBGM2h9Y6vX5hzcxlXLU7R7uu o3empYbTqbPmS6W8E4c0qGUBQpxINJomzIOZ5k4Fuxv16TSDT+2kkfID/qERAP9F8t8ZlED6dFPq4 b3Lcv6JJw==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kL5wm-0003WP-Gt; Wed, 23 Sep 2020 14:40:40 +0000 Received: from [2002:c35c:fd02::1] (helo=ZenIV.linux.org.uk) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kL5we-0003U7-1I for linux-arm-kernel@lists.infradead.org; Wed, 23 Sep 2020 14:40:33 +0000 Received: from viro by ZenIV.linux.org.uk with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kL5wX-004avv-5G; Wed, 23 Sep 2020 14:40:25 +0000 Date: Wed, 23 Sep 2020 15:40:25 +0100 From: Al Viro To: Christoph Hellwig Subject: Re: [PATCH 3/9] iov_iter: refactor rw_copy_check_uvector and import_iovec Message-ID: <20200923144025.GL3421308@ZenIV.linux.org.uk> References: <20200923060547.16903-1-hch@lst.de> <20200923060547.16903-4-hch@lst.de> <20200923141654.GJ3421308@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200923141654.GJ3421308@ZenIV.linux.org.uk> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200923_104032_216236_34879651 X-CRM114-Status: GOOD ( 21.57 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-aio@kvack.org, linux-mips@vger.kernel.org, David Howells , linux-mm@kvack.org, keyrings@vger.kernel.org, sparclinux@vger.kernel.org, linux-arch@vger.kernel.org, linux-s390@vger.kernel.org, linux-scsi@vger.kernel.org, Linus Torvalds , Arnd Bergmann , linux-block@vger.kernel.org, io-uring@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Jens Axboe , linux-parisc@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, David Laight , linux-fsdevel@vger.kernel.org, Andrew Morton , linuxppc-dev@lists.ozlabs.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Sep 23, 2020 at 03:16:54PM +0100, Al Viro wrote: > On Wed, Sep 23, 2020 at 08:05:41AM +0200, Christoph Hellwig wrote: > > > +struct iovec *iovec_from_user(const struct iovec __user *uvec, > > + unsigned long nr_segs, unsigned long fast_segs, > > Hmm... For fast_segs unsigned long had always been ridiculous > (4G struct iovec on caller stack frame?), but that got me wondering about > nr_segs and I wish I'd thought of that when introducing import_iovec(). > > The thing is, import_iovec() takes unsigned int there. Which is fine > (hell, the maximal value that can be accepted in 1024), except that > we do pass unsigned long syscall argument to it in some places. > > E.g. vfs_readv() quietly truncates vlen to 32 bits, and vlen can > come unchanged through sys_readv() -> do_readv() -> vfs_readv(). > With unsigned long passed by syscall glue. > > AFAICS, passing 4G+1 as the third argument to readv(2) on 64bit box > will be quietly treated as 1 these days. Which would be fine, except > that before "switch {compat_,}do_readv_writev() to {compat_,}import_iovec()" > it used to fail with -EINVAL. > > Userland, BTW, describes readv(2) iovcnt as int; process_vm_readv(), > OTOH, has these counts unsigned long from the userland POV... > > I suppose we ought to switch import_iovec() to unsigned long for nr_segs ;-/ > Strictly speaking that had been a userland ABI change, even though nothing > except regression tests checking for expected errors would've been likely > to notice. And it looks like no regression tests covered that one... > > Linus, does that qualify for your "if no userland has noticed the change, > it's not a breakage"? Egads... We have sys_readv() with unsigned long for file descriptor, since 1.3.31 when it had been introduced. And originally it did comparison with NR_OPEN right in sys_readv(). Then in 2.1.60 it had been switched to fget(), which used to take unsigned long at that point. And in 2.1.90pre1 it went unsigned int, so non-zero upper 32 bits in readv(2) first argument ceased to cause EBADF... Of course, libc had it as int fd all along. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel