linux-kernel - Re: [PATCH v3 1/2] x86/ioremap: fix the pfn calculation mistake in __ioremap_check

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Date:   Thu, 1 Jul 2021 07:41:40 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Yaohui Wang <yaohuiwang@...ux.alibaba.com>,
        dave.hansen@...ux.intel.com, tglx@...utronix.de
Cc:     luto@...nel.org, peterz@...radead.org, mingo@...hat.com,
        bp@...en8.de, x86@...nel.org, linux-kernel@...r.kernel.org,
        luoben@...ux.alibaba.com, Tom Lendacky <thomas.lendacky@....com>,
        Brijesh Singh <brijesh.singh@....com>
Subject: Re: [PATCH v3 1/2] x86/ioremap: fix the pfn calculation mistake in
 __ioremap_check_ram()

On 6/21/21 5:34 AM, Yaohui Wang wrote:
> For example, suppose memory range [phys_addr ~ phys_addr + PAGE_SIZE - 1]
> is a normal RAM page. ioremap(phys_addr, PAGE_SIZE - 1) will succeed
> (but it should not) because the pfn wrapping prevents this page to be
> checked whether it touches non-ioremappable resources.

I would have expected such a scenario to get caught by this check:

	if ((res->flags & IORESOURCE_SYSTEM_RAM) != IORESOURCE_SYSTEM_RAM)
		return false;

Was this issue found by inspection, or is it causing an actual problem
in practice?

Also, it would be really nice to include the original authors when you
send Fixes: for patches.  BTW, scripts/get_maintainer.pl would have done
this for you.  I've added Tom and Brijesh.  Please cc them in the future.