From: Shyam Thombre <sthombre@codeaurora.org>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: mark.rutland@arm.com, sashal@kernel.org,
anshuman.khandual@arm.com, will.deacon@arm.com,
linux-kernel@vger.kernel.org, jcrouse@codeaurora.org,
ard.biesheuvel@arm.com, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] arm64: mm: reset address tag set by kasan sw tagging
Date: Fri, 12 Jun 2020 19:27:14 +0530 [thread overview]
Message-ID: <809f4dc3-cba1-25b9-36cf-492e3b434530@codeaurora.org> (raw)
In-Reply-To: <20200610113626.GI26099@gaia>
Hi Catalin,
On 6/10/2020 5:06 PM, Catalin Marinas wrote:
> On Wed, Jun 10, 2020 at 04:39:44PM +0530, Shyam Thombre wrote:
>> KASAN sw tagging sets a random tag of 8 bits in the top byte of the pointer
>> returned by the memory allocating functions. So for the functions unaware
>> of this change, the top 8 bits of the address must be reset which is done
>> by the function arch_kasan_reset_tag().
>>
>> Signed-off-by: Shyam Thombre <sthombre@codeaurora.org>
>> ---
>> arch/arm64/mm/mmu.c | 1 +
>> 1 file changed, 1 insertion(+)
>>
>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
>> index e7fbc62..eae7655 100644
>> --- a/arch/arm64/mm/mmu.c
>> +++ b/arch/arm64/mm/mmu.c
>> @@ -723,6 +723,7 @@ int kern_addr_valid(unsigned long addr)
>> pmd_t *pmdp, pmd;
>> pte_t *ptep, pte;
>>
>> + addr = arch_kasan_reset_tag(addr);
>> if ((((long)addr) >> VA_BITS) != -1UL)
>> return 0;
>
> It would be interesting to know what fails without this patch. The only
> user seems to be read_kcore() and, at a quick look, I don't see how it
> can generate tagged addresses.
>
This issue is seen in downstream GPU drivers. It currently doesn't look
to impact any upstream users.
--
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project
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next prev parent reply other threads:[~2020-06-12 13:58 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-10 11:09 [PATCH] arm64: mm: reset address tag set by kasan sw tagging Shyam Thombre
2020-06-10 11:36 ` Catalin Marinas
2020-06-12 13:57 ` Shyam Thombre [this message]
2020-06-15 16:34 ` Will Deacon
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