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=-13.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 C6732C4338F for ; Sat, 14 Aug 2021 19:56:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9973760F92 for ; Sat, 14 Aug 2021 19:56:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229612AbhHNT5R (ORCPT ); Sat, 14 Aug 2021 15:57:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36082 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229489AbhHNT5Q (ORCPT ); Sat, 14 Aug 2021 15:57:16 -0400 Received: from mail-oi1-x234.google.com (mail-oi1-x234.google.com [IPv6:2607:f8b0:4864:20::234]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 49CFCC061764 for ; Sat, 14 Aug 2021 12:56:48 -0700 (PDT) Received: by mail-oi1-x234.google.com with SMTP id r5so21052654oiw.7 for ; Sat, 14 Aug 2021 12:56:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=uRfwNgrD75JLYmXwUCtNm9bkZCtiGwp3ZGULtH2XEO4=; b=lQry2peiAvYsJLE7aDmAKfikUFAOe7vLpHS2u/LJqnvVVu5sg9BjZ5DuI4efajI+iY 1Ay+38DqTSMM7Nfog5kLcTQ5PvwqyTLGkUPh9hXIzObRvWG/6Y5C+bZUcw3bjHFfix31 rQpocdn4X9K/wGL1XdZHVH5SuGTbyPhni/eN3nEcqxgp8pkjhvssjqNK9XwBX+uObXE4 qqX6L/eG9hXh5tCTgTsUnG1GhgD8Bi4CwOsCPUWTpLcJ+ArMpyqCPYLVKPcYW37PpeWX HJQKsO4Elm86JOrmLuY5dzdrEbomAJ6K7V9l4nbfwRoQjV5Z/mXi6pbF+6nVmZoXHnzq 3k8Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to; bh=uRfwNgrD75JLYmXwUCtNm9bkZCtiGwp3ZGULtH2XEO4=; b=grDY3jV0oc1CkQ8/N2SE43EpzNzI7d8hblg0PemR2axPKhduwp8g2TlLVz9nwr/35Q 37MOHIwIXDZC06l3pav7vMNgFavq/XvSc1Ie6kELOIV6I5gWD26C9L2W+yRt45F5P+9m 5IbenlaNh6kCwOMribC5cBdqk2OCpIHvlM6fklFO7OAJrwvsmHg/Pw1NkPmuD1pH6zEV 5F3yoODjT8KAKAuTFdQbOdqQpzLZiMxAfz4LxaKgYeUiZbLioX74YSXJOrZfb0YM8Nrc aTvISg2uywFsWrZcCEaSB/u+Bztif7lsNJ2/LgQN78ca61ErO7THFzDN9I9WN3d2JbFj 5iZw== X-Gm-Message-State: AOAM533xjs7bp5iHUcLIaP8/cKLFBmy5sUzmuf1kqYu0RT5NTiBAV9+v 7OGrhvNVpOZR14vJ4jLDNVA= X-Google-Smtp-Source: ABdhPJwyV5fd6zsa40uJADmxGsrlpE1atAPhrIqS2ewDjytgVbTqMWSKV9/1t4xiYjHbQpvj+PwYlw== X-Received: by 2002:aca:5c57:: with SMTP id q84mr6480107oib.159.1628971007710; Sat, 14 Aug 2021 12:56:47 -0700 (PDT) Received: from server.roeck-us.net ([2600:1700:e321:62f0:329c:23ff:fee3:9d7c]) by smtp.gmail.com with ESMTPSA id h6sm1190325otu.16.2021.08.14.12.56.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 14 Aug 2021 12:56:47 -0700 (PDT) Sender: Guenter Roeck Date: Sat, 14 Aug 2021 12:56:46 -0700 From: Guenter Roeck To: Stanislav German-Evtushenko Cc: Wim Van Sebroeck , linux-watchdog@vger.kernel.org Subject: Re: [PATCH] watchdog: Device must be opened for writing Message-ID: <20210814195646.GB3951799@roeck-us.net> References: <20210814191345.27221-1-ginermail@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210814191345.27221-1-ginermail@gmail.com> Precedence: bulk List-ID: X-Mailing-List: linux-watchdog@vger.kernel.org On Sun, Aug 15, 2021 at 04:13:45AM +0900, Stanislav German-Evtushenko wrote: > If userspace opens the watchdog device self-feeding stops. Sometimes > opening the device happens by accident, e.g. by mistakenly running grep > recursively in a wrong directory which leads to the server being reset. > > Watchdog device does not handle read operation therefore the issue can be > prevented by requiring the device to be opened for writing: > > - Prevent opening the device without FMODE_WRITE > > Signed-off-by: Stanislav German-Evtushenko NACK. That would be a major undocumented ABI change. Opening /dev/watchdog for reading can be and is used today to test a watchdog. Guenter > --- > drivers/watchdog/watchdog_dev.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c > index 3bab32485273..28b88542a4d0 100644 > --- a/drivers/watchdog/watchdog_dev.c > +++ b/drivers/watchdog/watchdog_dev.c > @@ -835,6 +835,10 @@ static int watchdog_open(struct inode *inode, struct file *file) > bool hw_running; > int err; > > + /* Must be open for writing */ > + if (!(file->f_mode & FMODE_WRITE)) > + return -EINVAL; > + > /* Get the corresponding watchdog device */ > if (imajor(inode) == MISC_MAJOR) > wd_data = old_wd_data; > > base-commit: cf813c67d9619fd474c785698cbed543b94209dd > -- > 2.25.1 >