From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from madras.collabora.co.uk (madras.collabora.co.uk [46.235.227.172]) by gabe.freedesktop.org (Postfix) with ESMTPS id 7EAE310E334 for ; Mon, 6 Nov 2023 14:43:28 +0000 (UTC) Message-ID: Date: Mon, 6 Nov 2023 14:43:23 +0000 MIME-Version: 1.0 Content-Language: en-US To: Vignesh Raman , bhanuprakash.modem@intel.com, igt-dev@lists.freedesktop.org References: <20231027144022.2016354-1-vignesh.raman@collabora.com> <797dd2bf-25a3-4a6a-b2eb-5c5cbdb25b09@collabora.com> From: Daniel Stone In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [igt-dev] [PATCH i-g-t v2] lib/igt_kms: Fix memory corruption List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: helen.koike@collabora.com Errors-To: igt-dev-bounces@lists.freedesktop.org Sender: "igt-dev" List-ID: Hi Vignesh, On 06/11/2023 02:40, Vignesh Raman wrote: > Hi Daniel, > > On 27/10/23 22:07, Daniel Stone wrote: >> Hi Vignesh, >> >> On 27/10/2023 15:40, Vignesh Raman wrote: >>> In crosvm, the kernel reports 16 for count_crtcs, which exceeds >>> IGT_MAX_PIPES set to 8. The function igt_display_require allocates >>> memory for IGT_MAX_PIPES members of igt_pipe_t structures, but then >>> writes into it based on the count_crtcs reported by the kernel, >>> resulting in memory corruption. >> >> To make this robust against future changes (32 CRTCs seems totally >> fanciful, but so did 16 a while ago), this needs to also be robust >> against count_crtcs exceeding IGT_NUM_PIPES, along the lines of your >> previous change. > > Yes, I agree to make the code robust against potential changes in the > future. We can set IGT_MAX_PIPES to 32. I will send an updated patch. What I mean is to make sure that the code cannot access out of bounds, regardless of the number. We can set IGT_MAX_PIPES to 32 but then someone will hit the same failure when there are more CRTCs than that. The way to do this would probably be to igt_require() that count_crtcs does not exceed IGT_MAX_PIPES, in all the paths where we access the crtcs array. There is no need to bump the limit to 32 until it's required. Cheers, Daniel