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Date:   Mon, 18 Jul 2022 14:37:53 -0700
From:   "Luck, Tony" <tony.luck@intel.com>
To:     Jane Chu <jane.chu@oracle.com>
Cc:     "Williams, Dan J" <dan.j.williams@intel.com>,
        "bp@alien8.de" <bp@alien8.de>,
        "tglx@linutronix.de" <tglx@linutronix.de>,
        "mingo@redhat.com" <mingo@redhat.com>,
        "dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
        "x86@kernel.org" <x86@kernel.org>,
        "linux-edac@vger.kernel.org" <linux-edac@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "hch@lst.de" <hch@lst.de>,
        "nvdimm@lists.linux.dev" <nvdimm@lists.linux.dev>
Subject: Re: [PATCH v3] x86/mce: retrieve poison range from hardware
Message-ID: <YtXSsUmh5XcVXGa3@agluck-desk3.sc.intel.com>
References: <20220717234805.1084386-1-jane.chu@oracle.com>
 <41db4a4b17a848798e487a058a2bc237@intel.com>
 <62d5b13b2cf1a_9291929433@dwillia2-xfh.jf.intel.com.notmuch>
 <797a2b64ed0949b6905b3c3e8f049a23@intel.com>
 <5a92e418-9f50-8212-92a0-4ac39cefa9ef@oracle.com>
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On Mon, Jul 18, 2022 at 09:11:33PM +0000, Jane Chu wrote:
> On 7/18/2022 12:22 PM, Luck, Tony wrote:
> >> It appears the kernel is trusting that ->physical_addr_mask is non-zero
> >> in other paths. So this is at least equally broken in the presence of a
> >> broken BIOS. The impact is potentially larger though with this change,
> >> so it might be a good follow-on patch to make sure that
> >> ->physical_addr_mask gets fixed up to a minimum mask value.
> > 
> > Agreed. Separate patch to sanitize early, so other kernel code can just use it.
> > 
> 
> Is it possible that with
>    if (mem->validation_bits & CPER_MEM_VALID_PA_MASK)
> the ->physical_addr_mask is still untrustworthy?

The validation_bits just show which fields the BIOS *says* it filled in.
If a validation bit isn't set, then Linux should certainly ignore that
field. But if it is set, then Linux needs to decide whether to use the
value, or do a sanity check first.

-Tony