From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 BA3791F9A83; Wed, 12 Feb 2025 10:33:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739356413; cv=none; b=ABTvYvJVIykOsUvigokedw/FM4PHHW6zK3IEBNfjWD1qKsur9vnt9rR9tkEqiKXfJJqA79zXGer+ga491KaqSnoIgPhhUnS4IOFH6F879NHzkAz2MnxxJiGq5w7YGWjfCGj8sV96TfSrGlW7dk7a/b383+AO3ydzqUUP+yhX3n0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739356413; c=relaxed/simple; bh=JjXhB+/E2GYRT9cPPM8Yrb46y4WEBtQtoQZkMTTIIsU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=rqoR3e9bMUA2vpedYLn13MkDciBUiYB1kIprWmTbnRt1QXkSaLYf+JKgYKQfkn7iJ35ldKNOlAup1zzJoT0Fi4zQT1CPwYZl+cF17y29j1yRFpQtZOAA2YppkSA0LSJmZud5FPaOpmAusJYcDLzr0OKgaCeQkpxsnML/txUPY+Q= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=apDjr8av; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="apDjr8av" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B1D81C4CEDF; Wed, 12 Feb 2025 10:33:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1739356413; bh=JjXhB+/E2GYRT9cPPM8Yrb46y4WEBtQtoQZkMTTIIsU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=apDjr8avlkhnXF3iYJxdGj3L2E/iuYjYY0W+1VgglUF2zyfjUBWv/QfwhUWcaktWx f9zy5MauWALBXh1TzaiMxPgJc5g3WqukiknGRksl/qBTThVZopPV23wgS/UC91rcMT y/gN3QnR5SLCS9sxxG+8vIxJT9FZ2OwGzBnbTURQT8aczBtFfJYvJ5mkQtfx59UXvn pHMA1MLQ3ZKAPDKLMreZ7FRFiL+lASvFeKqtNzzTftT6xA9rQ1FD6csCO/Vmj0bBy4 2VrLr0k5JgYH3PusfRJfAiNhPBF5evGq/gRaKsEJqxPnm6BQqdXB3FAbX5H05tKNkA Mr68rTFdKG2IA== Date: Wed, 12 Feb 2025 11:33:27 +0100 From: Lorenzo Pieralisi To: Oliver Upton Cc: linux-acpi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Hanjun Guo , Sudeep Holla , Will Deacon , Catalin Marinas , Marc Zyngier , Zheng Zengkai Subject: Re: [PATCH] ACPI: GTDT: Relax sanity checking on Platform Timers array count Message-ID: References: <20250128001749.3132656-1-oliver.upton@linux.dev> Precedence: bulk X-Mailing-List: linux-acpi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Tue, Jan 28, 2025 at 12:42:24PM -0800, Oliver Upton wrote: > Hi Lorenzo, > > On Tue, Jan 28, 2025 at 11:50:55AM +0100, Lorenzo Pieralisi wrote: > > > @@ -188,13 +188,17 @@ int __init acpi_gtdt_init(struct acpi_table_header *table, > > > cnt++; > > > > > > if (cnt != gtdt->platform_timer_count) { > > > + cnt = min(cnt, gtdt->platform_timer_count); > > > > Thank you for reporting this. > > > > There is something I need to understand. > > > > What's wrong cnt (because platform_timer_valid() fails for some > > reason on some entries whereas before the commit we > > are fixing was applied we *were* parsing those entries) or > > gtdt->platform_timer_count ? > > > > I *guess* the issue is the following: > > > > gtdt->platform_timer_count reports the number of GT blocks in the > > GTDT not including Arm generic watchdogs, whereas cnt counts both > > structure types (and that's what gtdt->platform_timer_count should > > report too if it was correct). > > I've seen two different issues so far: > > - In one case, the offset of the platform timer array is entirely > beyond the GTDT > > - In another, the GTDT has a timer array of length 2, but only the > first structure falls within the length of the overall GTDT > > Since cnt is the result of doing a bounds-checked walk of the platform > timer array, both of these issues cause the sanity check to fail. > > > > if (platform_timer_count) > > > - *platform_timer_count = gtdt->platform_timer_count; > > > + *platform_timer_count = cnt; > > > > I think this should be fine as things stand (but see above). > > > > It is used in: > > > > gtdt_sbsa_gwdt_init() - just to check if there are platform timers entries > > > > arch_timer_mem_acpi_init() - to create a temporary array to init arch mem timer > > entries (the array is oversized because it > > includes watchdog entries in the count) > > > > In both cases taking the > > > > min(cnt, gtdt->platform_timer_count); > > > > should work AFAICS > > It was probably worth noting in the changelog that I did this to > gracefully handle the reverse of this issue where we could dereference > platform timer entries that are within the bounds of the GTDT but exceed > gtdt->platform_timer_count. Hi Oliver, I was about to ask Catalin/Will to pick this up, don't know if you have time to update the changelog and send a v2 - a Link: to this thread will be added anyway. Thanks, Lorenzo