linux-kernel - Re: [PATCH] arm64: Fix kernel address detection of __is_lm

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Message-ID: <1fe8bff7-3ed2-ae96-e52b-dad59cd22539@arm.com>
Date:   Tue, 26 Jan 2021 18:37:39 +0000
From:   Vincenzo Frascino <vincenzo.frascino@....com>
To:     Catalin Marinas <catalin.marinas@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kasan-dev@...glegroups.com, stable@...r.kernel.org,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH] arm64: Fix kernel address detection of __is_lm_address()



On 1/26/21 4:36 PM, Catalin Marinas wrote:
> On Tue, Jan 26, 2021 at 01:40:56PM +0000, Vincenzo Frascino wrote:
>> Currently, the __is_lm_address() check just masks out the top 12 bits
>> of the address, but if they are 0, it still yields a true result.
>> This has as a side effect that virt_addr_valid() returns true even for
>> invalid virtual addresses (e.g. 0x0).
>>
>> Fix the detection checking that it's actually a kernel address starting
>> at PAGE_OFFSET.
>>
>> Fixes: f4693c2716b35 ("arm64: mm: extend linear region for 52-bit VA configurations")
>> Cc: <stable@...r.kernel.org> # 5.4.x
> 
> Not sure what happened with the Fixes tag but that's definitely not what
> it fixes. The above is a 5.11 commit that preserves the semantics of an
> older commit. So it should be:
> 
> Fixes: 68dd8ef32162 ("arm64: memory: Fix virt_addr_valid() using __is_lm_address()")
> 

Yes that is correct. I moved the release to which applies backword but I forgot
to update the fixes tag I suppose.

...

> 
> Anyway, no need to repost, I can update the fixes tag myself.
>

Thank you for this.

> In terms of stable backports, it may be cleaner to backport 7bc1a0f9e176
> ("arm64: mm: use single quantity to represent the PA to VA translation")
> which has a Fixes tag already but never made it to -stable. On top of
> this, we can backport Ard's latest f4693c2716b35 ("arm64: mm: extend
> linear region for 52-bit VA configurations"). I just tried these locally
> and the conflicts were fairly trivial.
> 

Ok, thank you for digging it. I will give it a try tomorrow.

-- 
Regards,
Vincenzo