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Date:   Tue, 02 Feb 2021 18:34:52 -0800 (PST)
Subject:     Re: [PATCH] riscv: virt_addr_valid must check the address belongs to linear mapping
In-Reply-To: <20210129173105.22020-1-alex@ghiti.fr>
CC:     Paul Walmsley <paul.walmsley@sifive.com>, aou@eecs.berkeley.edu,
        dvyukov@google.com, linux-riscv@lists.infradead.org,
        linux-kernel@vger.kernel.org, alex@ghiti.fr
From:   Palmer Dabbelt <palmer@dabbelt.com>
To:     alex@ghiti.fr
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On Fri, 29 Jan 2021 09:31:05 PST (-0800), alex@ghiti.fr wrote:
> virt_addr_valid macro checks that a virtual address is valid, ie that
> the address belongs to the linear mapping and that the corresponding
>  physical page exists.
>
> Add the missing check that ensures the virtual address belongs to the
> linear mapping, otherwise __virt_to_phys, when compiled with
> CONFIG_DEBUG_VIRTUAL enabled, raises a WARN that is interpreted as a
> kernel bug by syzbot.
>
> Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
> ---
>  arch/riscv/include/asm/page.h | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/arch/riscv/include/asm/page.h b/arch/riscv/include/asm/page.h
> index 2d50f76efe48..64a675c5c30a 100644
> --- a/arch/riscv/include/asm/page.h
> +++ b/arch/riscv/include/asm/page.h
> @@ -135,7 +135,10 @@ extern phys_addr_t __phys_addr_symbol(unsigned long x);
>
>  #endif /* __ASSEMBLY__ */
>
> -#define virt_addr_valid(vaddr)	(pfn_valid(virt_to_pfn(vaddr)))
> +#define virt_addr_valid(vaddr)	({						\
> +	unsigned long _addr = (unsigned long)vaddr;				\
> +	(unsigned long)(_addr) >= PAGE_OFFSET && pfn_valid(virt_to_pfn(_addr));	\
> +})
>
>  #define VM_DATA_DEFAULT_FLAGS	VM_DATA_FLAGS_NON_EXEC

Thanks, this is on fixes.