Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758692AbcLAMkq (ORCPT ); Thu, 1 Dec 2016 07:40:46 -0500 Received: from pandora.armlinux.org.uk ([78.32.30.218]:44860 "EHLO pandora.armlinux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758611AbcLAMkn (ORCPT ); Thu, 1 Dec 2016 07:40:43 -0500 Date: Thu, 1 Dec 2016 12:40:15 +0000 From: Russell King - ARM Linux To: Maninder Singh Cc: bcousson@baylibre.com, paul@pwsan.com, tony@atomide.com, linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, ajeet.y@samsung.com, pankaj.m@samsung.com, Vaneet Narang Subject: Re: [PATCH v2] mach-omap2: fixing wrong strcat for Non-NULL terminated string Message-ID: <20161201124015.GI23750@n2100.armlinux.org.uk> References: <1480589913-8839-1-git-send-email-maninder1.s@samsung.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1480589913-8839-1-git-send-email-maninder1.s@samsung.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2143 Lines: 61 On Thu, Dec 01, 2016 at 04:28:33PM +0530, Maninder Singh wrote: > variable name can have Non NULL terminated string after cropping > which may result strcat to fail, and cropping is not > required if (strlen(oh->name) + 8 < MOD_CLK_MAX_NAME_LEN). > > Issue caught with static analysis tool: > "Dangerous usage of 'name' (strncpy doesn't always 0-terminate it)" > > Signed-off-by: Vaneet Narang > Signed-off-by: Maninder Singh > --- > v1 -> v2: changed strncpy to strlcpy > arch/arm/mach-omap2/omap_hwmod.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/arch/arm/mach-omap2/omap_hwmod.c b/arch/arm/mach-omap2/omap_hwmod.c > index 759e1d4..582b95a 100644 > --- a/arch/arm/mach-omap2/omap_hwmod.c > +++ b/arch/arm/mach-omap2/omap_hwmod.c > @@ -742,12 +742,14 @@ static int _init_main_clk(struct omap_hwmod *oh) > char name[MOD_CLK_MAX_NAME_LEN]; > struct clk *clk; > > - /* +7 magic comes from '_mod_ck' suffix */ > - if (strlen(oh->name) + 7 > MOD_CLK_MAX_NAME_LEN) > + /* +8 magic comes from strlen("_mod_ck") added as suffix */ > + if (strlen(oh->name) + 8 > MOD_CLK_MAX_NAME_LEN) { > pr_warn("%s: warning: cropping name for %s\n", __func__, > oh->name); > + strlcpy(name, oh->name, MOD_CLK_MAX_NAME_LEN - 7); > + } else > + strcpy(name, oh->name); > > - strncpy(name, oh->name, MOD_CLK_MAX_NAME_LEN - 7); > strcat(name, "_mod_ck"); > > clk = clk_get(NULL, name); > -- > 1.9.1 > Simpler, clearer, and less error-prone: static const char modck[] = "_mod_ck"; if (strlen(oh->name) >= MOD_CLK_MAX_NAME_LEN - strlen(modck)) pr_warn("%s: warning: cropping name for %s\n", __func__, oh->name); strlcpy(name, oh->name, MOD_CLK_MAX_NAME_LEN - strlen(modck)); strlcat(name, modck, MOD_CLK_MAX_NAME_LEN); Note that the length argument to strlcpy _includes_ the NUL terminator. Also note the use of strlcat() which ensures that it won't overflow the buffer. -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net.