From patchwork Tue Mar 13 19:51:03 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Salvatore Mesoraca X-Patchwork-Id: 10280647 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id ADC076038F for ; Tue, 13 Mar 2018 19:52:24 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 9B2A62843C for ; Tue, 13 Mar 2018 19:52:24 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 99C802841C; Tue, 13 Mar 2018 19:52:24 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.3 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, FREEMAIL_FROM, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.wl.linuxfoundation.org (Postfix) with SMTP id 07E1C2859A for ; Tue, 13 Mar 2018 19:51:31 +0000 (UTC) Received: (qmail 11968 invoked by uid 550); 13 Mar 2018 19:51:30 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Delivered-To: mailing list kernel-hardening@lists.openwall.com Received: (qmail 11943 invoked from network); 13 Mar 2018 19:51:29 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id; bh=Z5p+IFringKLuINSVeFM5lLckFQhbotJDTQeKdVAK6E=; b=tEORs4ztn7UylOJns210BbS8ZsnHsr0gNvD2soRT8xzSM8CjAkv2E1hyuWnNPA2gFw dEuFo9jhzWsQknkVgFxE9qJuUqdh/MlhV0fGmL4o3bMONIn39A3cYZTGEfc1lEmEFbZs FQ3mPJ0Fz7DBEDM5/ium/Gd6CRb0KPKOhYESqjsfTngj8hCRmVvjXQOy3OweQCCqWQXY 2F/ioBDKTEe7hckRAaKJGDWlH+pj3TuadoL7gmG9BoG7rCmU827GkT8Mb3D5WWAzUgjV 4bkLxLAW5Xuh2xslTyEwwz0YnhxhGCB9tBI+OPRXQnfh2yXh/QYtmpAmHnQUZJ7HJlUh Z5eQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id; bh=Z5p+IFringKLuINSVeFM5lLckFQhbotJDTQeKdVAK6E=; b=FNPz6F5h8tYTk4oubpzbcmQpEMDPz92QOewpQ4UsIO1NDFa1SlGObwvtIHvi5EDEpd ijsCY91uD9i954zLvhNWHfxbivujZOwwrUvN4bk0L+SPamAVilsnRUmFjXYNxqmo6bAe 9fUQQKqxec7hBlP0Wdayi8oQVBQ+ESIfMgtbpw5xWU56SF14wDJ7FmytcLL399WliDi1 Ys4EbGhzUIZx4ElhJHgvZbi13saxEG+iTtypRCv2cAHeZBvwxkR3hVj1AHHPsn9rUP8S aNYIl7i/ZiNEzDmQX0xK8X7bLhpa+kWquuEBk/lUTCaCVSjFO/x60wC5T0mXvMeIcDop 2opw== X-Gm-Message-State: AElRT7H8WSbCo53kjKL3swYm+Oxd3d50PpeSUcNDWG55MzlVzBStsqsW hoilIoQWfMIJPFAm52Ffp+m4jgQ7nag= X-Google-Smtp-Source: AG47ELukNESDtQ9wIv/CqAJuQzL+3550rOds3b2QYe1ImrVeBwwdMKbMxhxim2tNQmNaf8TFrs3yeQ== X-Received: by 10.28.172.202 with SMTP id v193mr1694393wme.129.1520970678258; Tue, 13 Mar 2018 12:51:18 -0700 (PDT) From: Salvatore Mesoraca To: linux-kernel@vger.kernel.org Cc: kernel-hardening@lists.openwall.com, Ingo Molnar , Kees Cook , Salvatore Mesoraca , Steven Rostedt Subject: [PATCH] ftrace: drop a VLA in module_exists() Date: Tue, 13 Mar 2018 20:51:03 +0100 Message-Id: <1520970663-19633-1-git-send-email-s.mesoraca16@gmail.com> X-Mailer: git-send-email 1.9.1 X-Virus-Scanned: ClamAV using ClamSMTP Avoid a VLA[1] by using a real constant expression instead of a variable. The compiler should be able to optimize the original code and avoid using an actual VLA. Anyway this change is useful because it will avoid a false positive with -Wvla, it might also help the compiler generating better code. [1] https://lkml.org/lkml/2018/3/7/621 Signed-off-by: Salvatore Mesoraca --- kernel/trace/ftrace.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index eac9ce2..adebb92 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -3902,14 +3902,13 @@ static bool module_exists(const char *module) { /* All modules have the symbol __this_module */ const char this_mod[] = "__this_module"; - const int modname_size = MAX_PARAM_PREFIX_LEN + sizeof(this_mod) + 1; - char modname[modname_size + 1]; + char modname[MAX_PARAM_PREFIX_LEN + sizeof(this_mod) + 1]; unsigned long val; int n; - n = snprintf(modname, modname_size + 1, "%s:%s", module, this_mod); + n = snprintf(modname, sizeof(modname), "%s:%s", module, this_mod); - if (n > modname_size) + if (n > sizeof(modname) - 1) return false; val = module_kallsyms_lookup_name(modname);