Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20210129173105.22020-1-alex@ghiti.fr>
In-Reply-To: <20210129173105.22020-1-alex@ghiti.fr>
From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Sun, 31 Jan 2021 11:00:12 +0100
Message-ID: <CACT4Y+bPy-XpynfRvUbE-wSXnGe_AitusJ=2cANdb-O0ONtgtw@mail.gmail.com>
Subject: Re: [PATCH] riscv: virt_addr_valid must check the address belongs to
 linear mapping
To:     Alexandre Ghiti <alex@ghiti.fr>
Cc:     Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        linux-riscv <linux-riscv@lists.infradead.org>,
        LKML <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Fri, Jan 29, 2021 at 6:31 PM Alexandre Ghiti <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.

Thanks, Alexandre. Much appreciated.

> 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
>
> --
> 2.20.1
>