linux-kernel - Re: [PATCH v5 1/4] cacheinfo: Check for null last-level cache info

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Message-ID: <20240901180719.GA4089@alberich>
Date: Sun, 1 Sep 2024 20:07:19 +0200
From: Andreas Herrmann <aherrmann@...e.de>
To: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Cc: x86@...nel.org, Andreas Herrmann <aherrmann@...e.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Chen Yu <yu.c.chen@...el.com>, Len Brown <len.brown@...el.com>,
	Radu Rendec <rrendec@...hat.com>,
	Pierre Gondois <Pierre.Gondois@....com>, Pu Wen <puwen@...on.cn>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Sudeep Holla <sudeep.holla@....com>,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
	Will Deacon <will@...nel.org>, Zhang Rui <rui.zhang@...el.com>,
	Nikolay Borisov <nik.borisov@...e.com>,
	Huang Ying <ying.huang@...el.com>,
	Ricardo Neri <ricardo.neri@...el.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 1/4] cacheinfo: Check for null last-level cache info

On Mon, Aug 26, 2024 at 10:16:32PM -0700, Ricardo Neri wrote:
> Before determining the validity of the last-level cache info, ensure that
> it has been allocated. Simply checking for non-zero cache_leaves() is not
> sufficient, as some architectures (e.g., Intel processors) have non-zero
> cache_leaves() before allocation.
> 
> Dereferencing NULL cacheinfo can occur in update_per_cpu_data_slice_size().
> This function iterates over all online CPUs. However, a CPU may have come
> online recently, but its cacheinfo may not have been allocated yet.
> 
> Reviewed-by: Sudeep Holla <sudeep.holla@....com>
> Signed-off-by: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>

Reviewed-by: Andreas Herrmann <aherrmann@...e.de>
Tested-by: Andreas Herrmann <aherrmann@...e.de>

Test was done with a system equipped with AMD Phenom II X6 1055T and
test kernels based on v6.11-rc5-176-g20371ba12063.


Thanks,
Andreas