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=-3.8 required=3.0 tests=BAYES_00,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 2FE15C2BB84 for ; Mon, 7 Sep 2020 11:58:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D4E0F207C3 for ; Mon, 7 Sep 2020 11:58:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=baylibre-com.20150623.gappssmtp.com header.i=@baylibre-com.20150623.gappssmtp.com header.b="hmebUBbh" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729004AbgIGL6Q (ORCPT ); Mon, 7 Sep 2020 07:58:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48054 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729172AbgIGL6B (ORCPT ); Mon, 7 Sep 2020 07:58:01 -0400 Received: from mail-ej1-x642.google.com (mail-ej1-x642.google.com [IPv6:2a00:1450:4864:20::642]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EEDDBC061755 for ; Mon, 7 Sep 2020 04:58:00 -0700 (PDT) Received: by mail-ej1-x642.google.com with SMTP id r7so4523771ejs.11 for ; Mon, 07 Sep 2020 04:58:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=baylibre-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=wuNizNJ6r33hGWcPZZ5Js9EvkLS7jqpgkks6hNUFhPA=; b=hmebUBbhYKYjFws6DyXQmTbngYhFOaYQZwILguT9XWAVUF34AkgUhucL2X83PWUz3B O1WILkR2ETVUXAQHnmzJ3T9TOE+BkUDSmBuGiSgS6Sp5sXm97ReIQwhxpvCiXKPYPxwl KmYDUbghifyxlWCuz0FXLZhOP8/WaaBorOGjV0OaPvsg96+OJ9dsVtYXdMjZspZn4Z+G WnnS+fADtLeE8tiSTQ84zNr/1dJ4qnng0gSHl9HGGeZ9NF0QDxScyDw1+vyr5LVHsdpY BHAzbAA6yL4HFjfbQwk6s5dWCoCOvVuf2PpqzV88RAQnteHZ8G9AZHlHpHrnxdKi5Hax Gnmw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=wuNizNJ6r33hGWcPZZ5Js9EvkLS7jqpgkks6hNUFhPA=; b=QI2S6oCJ0I2iwEPS0l7rEnFj9CKnBdo0ZrmGOuY23lzBxLDP3kITbKOUhfG9bg5YGd Xlfv9iGNcYJcMU7O9k1nZtcjC8imUvca7FJgZDUCHjum5UJ/R7sA/GfmMiyQcsYWF4u5 hGVeWLaAiCaSG9e0uHUAv0ZFah3eHN8LUVU0VhUrxKBmfBUPd9Oqn7i3TNOWVNfg2MLN kD7zEZaEcwD3ofPtxpX1qc40SARoIe+ygndernL7SAb1hoy80hvhdAlZ/I3aopVFe2LL 6eRC/I8a2ih0OpxjBoz5lQT/Y3b9N1JLqnvDkk1bSr+f5iVSwF2xt7I3f/QJV6X3Ikgm j8sg== X-Gm-Message-State: AOAM533A2hY+scANB0/Xvg709S2KfwCRKbF8EP7kIQrr1IJ+bT2Ti3gM Hu5Jt2fDHum5Y4IbpyF9KncBO9R94EJgspgKs75QCQ== X-Google-Smtp-Source: ABdhPJy6SVnws0uCzDJjVt4W73YHn0MvifY/aOZ9PPy9nsKFI6ForeXnVBcXyVqA8gP/QTrekOcYQwHkOSe341Q0TzI= X-Received: by 2002:a17:906:174e:: with SMTP id d14mr3022559eje.225.1599479879319; Mon, 07 Sep 2020 04:57:59 -0700 (PDT) MIME-Version: 1.0 References: <20200904154547.3836-1-brgl@bgdev.pl> <20200904154547.3836-4-brgl@bgdev.pl> <20200904163517.GW1891694@smile.fi.intel.com> <20200907114551.GV1891694@smile.fi.intel.com> In-Reply-To: <20200907114551.GV1891694@smile.fi.intel.com> From: Bartosz Golaszewski Date: Mon, 7 Sep 2020 13:57:48 +0200 Message-ID: Subject: Re: [PATCH 03/23] lib: uaccess: provide getline_from_user() To: Andy Shevchenko Cc: Bartosz Golaszewski , Linus Walleij , Jonathan Corbet , Mika Westerberg , Kent Gibson , linux-gpio , linux-doc , LKML , ACPI Devel Maling List Content-Type: text/plain; charset="UTF-8" Sender: linux-gpio-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-gpio@vger.kernel.org On Mon, Sep 7, 2020 at 1:45 PM Andy Shevchenko wrote: > > On Mon, Sep 07, 2020 at 12:28:05PM +0200, Bartosz Golaszewski wrote: > > On Mon, Sep 7, 2020 at 12:19 PM Andy Shevchenko > > wrote: > > > > > > On Mon, Sep 7, 2020 at 1:05 PM Bartosz Golaszewski > > > wrote: > > > > On Fri, Sep 4, 2020 at 6:35 PM Andy Shevchenko > > > > wrote: > > > > > On Fri, Sep 04, 2020 at 05:45:27PM +0200, Bartosz Golaszewski wrote: > > > > > > From: Bartosz Golaszewski > > > > > > > > Doesn't mm/util.c provides us something like this? > > > > > strndup_user()? > > > > > > > > > > > > > Yes, there's both strndup_user() as well as strncpy_from_user(). The > > > > problem is that they rely on the strings being NULL-terminated. This > > > > is not guaranteed for debugfs file_operations write callbacks. We need > > > > some helper that takes the minimum of bytes provided by userspace and > > > > the buffer size and figure out how many bytes to actually copy IMO. > > > > > > Wouldn't this [1] approach work? > > > > > > [1]: https://elixir.bootlin.com/linux/v5.9-rc3/source/arch/x86/kernel/cpu/mtrr/if.c#L93 > > > > > > > Sure, but this is pretty much what I do in getline_from_user(). If > > anything we should port mtrr_write() to using getline_from_user() once > > it's available upstream, no? > > But you may provide getline_from_user() as inline in the same header where > strncpy_from_user() is declared. It will be like 3 LOCs? > May be more than that. I'll see what I can do. Bart