From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from ni.piap.pl (ni.piap.pl [195.187.100.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 718AB46B5; Fri, 3 Oct 2025 06:43:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=195.187.100.5 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759473796; cv=none; b=C8nXvHRoxJeE01HbY+737hq4WVl4VU4pSJ1J48cbyY7MsXqXwbQ5dIurls58PlorWzrpduP0Hl02AfU4UYP4tXaRoprtRzvMT9eK39UOdLDz/AoFgGlhZAr/kSK9PahSYtzURYmZ8ZS1NTq9gaozxACSPNfSLSh/t1M31rrbaGM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759473796; c=relaxed/simple; bh=0cB5I9OcBsrAyHHeP2qTFCp9rOKySUcatAIE98vMy40=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=N6XtGehzIpfi850fY4wTBzHdtoCA2b0ShDga6tPV8DXpQ+Ug66lh1iTeeOyOLcnzZJRBYJjQSt7G9ceXklhSaEs98sbUloPa9sOrieJaV1so2kJCWwmuM39K6j2/y9HOtRSPZOlWfopXvfW85ZSVQ5PYNepG6RoAQbSg2ZYaDKM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=piap.pl; spf=pass smtp.mailfrom=piap.pl; arc=none smtp.client-ip=195.187.100.5 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=piap.pl Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=piap.pl Received: from t19.piap.pl (OSB1819.piap.pl [10.0.9.19]) by ni.piap.pl (Postfix) with ESMTPS id 4D211C3EEAD7; Fri, 3 Oct 2025 08:34:01 +0200 (CEST) DKIM-Filter: OpenDKIM Filter v2.11.0 ni.piap.pl 4D211C3EEAD7 From: =?utf-8?Q?Krzysztof_Ha=C5=82asa?= To: Kriish Sharma Cc: khc@pm.waw.pl, andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] drivers/net/wan/hdlc_ppp: fix potential null pointer in ppp_cp_event logging In-Reply-To: <20251002180541.1375151-1-kriish.sharma2006@gmail.com> (Kriish Sharma's message of "Thu, 2 Oct 2025 18:05:41 +0000") References: <20251002180541.1375151-1-kriish.sharma2006@gmail.com> Sender: khalasa@piap.pl Date: Fri, 03 Oct 2025 08:34:01 +0200 Message-ID: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Hi Kriish, Kriish Sharma writes: > Fixes warnings observed during compilation with -Wformat-overflow: > > drivers/net/wan/hdlc_ppp.c: In function =E2=80=98ppp_cp_event=E2=80=99: > drivers/net/wan/hdlc_ppp.c:353:17: warning: =E2=80=98%s=E2=80=99 directiv= e argument is null [-Wformat-overflow=3D] > 353 | netdev_info(dev, "%s down\n", proto_name(pid)); > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > drivers/net/wan/hdlc_ppp.c:342:17: warning: =E2=80=98%s=E2=80=99 directiv= e argument is null [-Wformat-overflow=3D] > 342 | netdev_info(dev, "%s up\n", proto_name(pid)); > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ It appears proto_name(pid) never returns NULL there. Despite actually saying "return NULL", that's right :-) Perhaps you should change it to return "LCP" by default instead, and not only on PID_LCP? It should silence the compiler. This ppp_cp_event() is called in a few places: - ppp_cp_parse_cr() - ppp_rx() - ppp_timer() (with a known protocol, though) - and others, with PID_LCP. Now, before printing proto_name(pid), ppp_cp_event() does proto =3D get_proto(pid), and dereferences it :-) The pid seems to always come from ppp_rx(). Fortunately it's checked at start, and it case of an unknown proto it goes straight to rx_error. --=20 Krzysztof "Chris" Ha=C5=82asa Sie=C4=87 Badawcza =C5=81ukasiewicz Przemys=C5=82owy Instytut Automatyki i Pomiar=C3=B3w PIAP Al. Jerozolimskie 202, 02-486 Warszawa