linux-kernel - Re: [PATCH] Revert "mm/usercopy: Drop extra is_vmalloc_or

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Message-ID: <4b4f142a-8d32-e6f5-b9ff-8905bcefb77d@huawei.com>
Date:   Sat, 25 Dec 2021 20:00:21 +0800
From:   Kefeng Wang <wangkefeng.wang@...wei.com>
To:     Nicholas Piggin <npiggin@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Kees Cook <keescook@...omium.org>,
        Laura Abbott <labbott@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        Mark Rutland <mark.rutland@....com>,
        "Michael Ellerman" <mpe@...erman.id.au>,
        Paul Mackerras <paulus@...ba.org>
Subject: Re: [PATCH] Revert "mm/usercopy: Drop extra is_vmalloc_or_module()
 check"


On 2021/12/25 19:04, Nicholas Piggin wrote:
> Excerpts from Kefeng Wang's message of December 25, 2021 12:05 pm:
>
...
>>> Can you try that ?
>>>
>>> #define virt_addr_valid(kaddr)	((kaddr & PAGE_OFFSET) == PAGE_OFFSET &&
>>> pfn_valid(virt_to_pfn(kaddr)))
>> I got this commit,
>>
>> commit 4dd7554a6456d124c85e0a4ad156625b71390b5c
>>
>> Author: Nicholas Piggin <npiggin@...il.com>
>> Date:   Wed Jul 24 18:46:37 2019 +1000
>>
>>       powerpc/64: Add VIRTUAL_BUG_ON checks for __va and __pa addresses
>>
>>       Ensure __va is given a physical address below PAGE_OFFSET, and __pa is
>>       given a virtual address above PAGE_OFFSET.
>>
>> It has check the PAGE_OFFSET in __pa,  will test it and resend the
>> patch(with above warning changes).
> What did you get with this commit? Is this what causes the crash?

I mean that your patch does the check to make sure the virt addr should 
above PAGE_OFFSET,

and we can add the check in the virt_addr_valid too.

>
> riscv for example with flatmem also relies on pfn_valid to do the right
> thing, so as far as I can see the check should exclude vmalloc addresses
> and it's just a matter of virt_addr_valid not to give virt_to_pfn an
> address < PAGE_OFFSET.
>
> If we take riscv's implementation
>
> diff --git a/arch/powerpc/include/asm/page.h b/arch/powerpc/include/asm/page.h
> index 254687258f42..7713188516a6 100644
> --- a/arch/powerpc/include/asm/page.h
> +++ b/arch/powerpc/include/asm/page.h
> @@ -132,7 +132,10 @@ static inline bool pfn_valid(unsigned long pfn)
>   #define virt_to_page(kaddr)    pfn_to_page(virt_to_pfn(kaddr))
>   #define pfn_to_kaddr(pfn)      __va((pfn) << PAGE_SHIFT)
>   
> -#define virt_addr_valid(kaddr) pfn_valid(virt_to_pfn(kaddr))
> +#define virt_addr_valid(vaddr) ({                                      \
> +       unsigned long _addr = (unsigned long)vaddr;                     \
> +       (unsigned long)(_addr) >= PAGE_OFFSET && pfn_valid(virt_to_pfn(_addr)); \
> +})
Yes, I send a new v2  with this change, thanks
>   
>   /*
>    * On Book-E parts we need __va to parse the device tree and we can't
>
> .