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a="392876803" X-IronPort-AV: E=Sophos;i="6.04,235,1695711600"; d="scan'208";a="392876803" Received: from orsmga007.jf.intel.com ([10.7.209.58]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Nov 2023 01:18:32 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10908"; a="762242261" X-IronPort-AV: E=Sophos;i="6.04,235,1695711600"; d="scan'208";a="762242261" Received: from stinkpipe.fi.intel.com (HELO stinkbox) ([10.237.72.74]) by orsmga007.jf.intel.com with SMTP; 29 Nov 2023 01:18:25 -0800 Received: by stinkbox (sSMTP sendmail emulation); Wed, 29 Nov 2023 11:18:24 +0200 Date: Wed, 29 Nov 2023 11:18:24 +0200 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= To: Maxime Ripard Cc: Jani Nikula , Thomas Zimmermann , Emma Anholt , Jonathan Corbet , linux-kernel@vger.kernel.org, Samuel Holland , Sandy Huang , Jernej Skrabec , linux-doc@vger.kernel.org, Hans Verkuil , linux-rockchip@lists.infradead.org, Chen-Yu Tsai , dri-devel@lists.freedesktop.org, linux-media@vger.kernel.org, linux-sunxi@lists.linux.dev, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v4 05/45] drm/connector: Check drm_connector_init pointers arguments Message-ID: References: <20231128-kms-hdmi-connector-state-v4-0-c7602158306e@kernel.org> <20231128-kms-hdmi-connector-state-v4-5-c7602158306e@kernel.org> <87h6l66nth.fsf@intel.com> <2mnodqvu2oo674vspiy4gxhglu3it5cq47acx5itnbwevgc4cf@c7h2bvnx3m2n> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <2mnodqvu2oo674vspiy4gxhglu3it5cq47acx5itnbwevgc4cf@c7h2bvnx3m2n> X-Patchwork-Hint: comment X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20231129_011833_218517_B543271F X-CRM114-Status: GOOD ( 33.71 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Nov 29, 2023 at 10:11:26AM +0100, Maxime Ripard wrote: > Hi Ville, > = > On Tue, Nov 28, 2023 at 03:49:08PM +0200, Ville Syrj=E4l=E4 wrote: > > On Tue, Nov 28, 2023 at 02:29:40PM +0100, Maxime Ripard wrote: > > > On Tue, Nov 28, 2023 at 02:54:02PM +0200, Jani Nikula wrote: > > > > On Tue, 28 Nov 2023, Maxime Ripard wrote: > > > > > All the drm_connector_init variants take at least a pointer to the > > > > > device, connector and hooks implementation. > > > > > > > > > > However, none of them check their value before dereferencing those > > > > > pointers which can lead to a NULL-pointer dereference if the auth= or > > > > > isn't careful. > > > > = > > > > Arguably oopsing on the spot is preferrable when this can't be caus= ed by > > > > user input. It's always a mistake that should be caught early during > > > > development. > > > > = > > > > Not everyone checks the return value of drm_connector_init and frie= nds, > > > > so those cases will lead to more mysterious bugs later. And probably > > > > oopses as well. > > > = > > > So maybe we can do both then, with something like > > > = > > > if (WARN_ON(!dev)) > > > return -EINVAL > > > = > > > if (drm_WARN_ON(dev, !connector || !funcs)) > > > return -EINVAL; > > > = > > > I'd still like to check for this, so we can have proper testing, and = we > > > already check for those pointers in some places (like funcs in > > > drm_connector_init), so if we don't cover everything we're inconsiste= nt. > > = > > People will invariably cargo-cult this kind of stuff absolutely > > everywhere and then all your functions will have tons of dead > > code to check their arguments. > = > And that's a bad thing because... ? > = > Also, are you really saying that checking that your arguments make sense > is cargo-cult? > = > We're already doing it in some parts of KMS, so we have to be > consistent, and the answer to "most drivers don't check the error" > cannot be "let's just give on error checking then". > = > > I'd prefer not to go there usually. > > = > > Should we perhaps start to use the (arguably hideous) > > - void f(struct foo *bar) > > + void f(struct foo bar[static 1]) > > syntax to tell the compiler we don't accept NULL pointers? > > = > > Hmm. Apparently that has the same problem as using any > > other kind of array syntax in the prototype. That is, > > the compiler demands to know the definition of 'struct foo' > > even though we're passing in effectively a pointer. Sigh. > = > Honestly, I don't care as long as it's something we can unit-test to > make sure we make it consistent. We can't unit test a complete kernel > crash. Why do you want to put utterly broken code into a unit test? -- = Ville Syrj=E4l=E4 Intel _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel