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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 80DD0C41513 for ; Thu, 17 Aug 2023 16:56:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1353775AbjHQQzf (ORCPT ); Thu, 17 Aug 2023 12:55:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55114 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1353816AbjHQQzY (ORCPT ); Thu, 17 Aug 2023 12:55:24 -0400 Received: from mail-pj1-x102a.google.com (mail-pj1-x102a.google.com [IPv6:2607:f8b0:4864:20::102a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 099F32D5D for ; Thu, 17 Aug 2023 09:55:24 -0700 (PDT) Received: by mail-pj1-x102a.google.com with SMTP id 98e67ed59e1d1-26b51d4c985so2840135a91.3 for ; Thu, 17 Aug 2023 09:55:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; t=1692291323; x=1692896123; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=m8llPZ+qxlgNzlRp0B9M5wdmj0W8bnJMDksdaqRhUBE=; b=YawcbNyYYnvjNBYD+HILcUHRjqLAr2TlnBBW8usY5K7CtuQa/5DlIqUpZHR+6ol4C9 5sQL0xeUvPjghp3ozsfduSGSrg8lMmGuLMu1DPJgXrrCnanX+fJx+e/YdbNloohVyT2H yk0f6g7nmjDQwGZjFiGm3kJFprlhVfRFzWYn8= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1692291323; x=1692896123; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=m8llPZ+qxlgNzlRp0B9M5wdmj0W8bnJMDksdaqRhUBE=; b=eKAHZ7Va9d0bWP9puucEiVjqZyU4S8BPZCGXhgOnatPrrRIyzcnXGxOlq4HPixPJTe cewK0SERakk1lm0AmzVGP5sfIbik8MhkbUHgf2u87f1n3+4kEtOeut5978yjvKyVvz5n hYcPo2cnfN5vrSfy5z2iNUP/qahugNcNDOyTR/LBTw2ZNdP+uED8Snt3FsQaT1VAOBir fzAFszt8gKZiloAJu0hDH+fyDs6TCdy3Av0F6YUIotvBd24PaIvjdc5MG8VXUp5BmhHw DCH98I2Bl1bso9s+8qufJsoZpmKov1+6AjEkhMHrB27G2Z4I+XQzZ6IxWouTFduBIgW0 UDjA== X-Gm-Message-State: AOJu0YwcRBAEuG5rRlPNhUZanq5Q/dygecKn+eggDu3eMj3a6I2VTHZH XYcbS+Y5Zt1rcEHhR0RD8NWkSzQQ1ulHSzFMhYM= X-Google-Smtp-Source: AGHT+IH5wvBkfktFmJO8os+LqrwPdXSoQAnAih4GmxYrMQmYIoIP8A+YdeDd6zDTuXXCkRcTtteVrQ== X-Received: by 2002:a17:90b:230d:b0:263:3386:9da8 with SMTP id mt13-20020a17090b230d00b0026333869da8mr3965511pjb.49.1692291323346; Thu, 17 Aug 2023 09:55:23 -0700 (PDT) Received: from www.outflux.net (198-0-35-241-static.hfc.comcastbusiness.net. [198.0.35.241]) by smtp.gmail.com with ESMTPSA id 30-20020a17090a001e00b00263b9e75aecsm26796pja.41.2023.08.17.09.55.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 17 Aug 2023 09:55:22 -0700 (PDT) Date: Thu, 17 Aug 2023 09:55:22 -0700 From: Kees Cook To: "GONG, Ruiqi" Cc: Arnd Bergmann , Greg Kroah-Hartman , linux-kernel@vger.kernel.org, gongruiqi1@huawei.com Subject: Re: [PATCH] lkdtm: use the return value of strim() Message-ID: <202308170954.B18CCA9@keescook> References: <20230817142117.972418-1-gongruiqi@huaweicloud.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230817142117.972418-1-gongruiqi@huaweicloud.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 17, 2023 at 10:21:17PM +0800, GONG, Ruiqi wrote: > From: "GONG, Ruiqi" > > Make use of the return value of strim() to achieve left-trim as well as > right-trim, which prevents the following unusual fail case: > > # echo " EXCEPTION" > /sys/kernel/debug/provoke-crash/DIRECT > sh: write error: Invalid argument > > Link: https://github.com/KSPP/linux/issues/337 > Signed-off-by: GONG, Ruiqi > --- > drivers/misc/lkdtm/core.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c > index 0772e4a4757e..812c96461ab2 100644 > --- a/drivers/misc/lkdtm/core.c > +++ b/drivers/misc/lkdtm/core.c > @@ -242,7 +242,7 @@ static ssize_t lkdtm_debugfs_entry(struct file *f, > } > /* NULL-terminate and remove enter */ > buf[count] = '\0'; > - strim(buf); > + buf = strim(buf); > > crashtype = find_crashtype(buf); > free_page((unsigned long)buf); Will free_page() still work in this case, though? The address won't match the allocation any more... -Kees > @@ -318,7 +318,7 @@ static ssize_t direct_entry(struct file *f, const char __user *user_buf, > } > /* NULL-terminate and remove enter */ > buf[count] = '\0'; > - strim(buf); > + buf = strim(buf); > > crashtype = find_crashtype(buf); > free_page((unsigned long) buf); > -- > 2.25.1 > -- Kees Cook