linux-kernel - Re: [PATCH] arm64/vdso: don't leak kernel addresses

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Date:   Mon, 1 Apr 2019 08:39:02 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Matteo Croce <mcroce@...hat.com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>
Subject: Re: [PATCH] arm64/vdso: don't leak kernel addresses

On Sat, Mar 30, 2019 at 07:46:38PM +0100, Matteo Croce wrote:
> Since commit ad67b74d2469d9b8 ("printk: hash addresses printed with %p"),
> two obfuscated kernel pointer are printed at every boot:
> 
>     vdso: 2 pages (1 code @ (____ptrval____), 1 data @ (____ptrval____))
> 
> Remove the addresses from the print, which turns into a more discrete:
> 
>     vdso: 2 pages (1 code, 1 data)
> 
> Fixes: ad67b74d2469d9b8 ("printk: hash addresses printed with %p")
> Signed-off-by: Matteo Croce <mcroce@...hat.com>
> ---
>  arch/arm64/kernel/vdso.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
> index 2d419006ad43..fdfee0ef5bc5 100644
> --- a/arch/arm64/kernel/vdso.c
> +++ b/arch/arm64/kernel/vdso.c
> @@ -146,8 +146,8 @@ static int __init vdso_init(void)
>  	}
>  
>  	vdso_pages = (vdso_end - vdso_start) >> PAGE_SHIFT;
> -	pr_info("vdso: %ld pages (%ld code @ %p, %ld data @ %p)\n",
> -		vdso_pages + 1, vdso_pages, vdso_start, 1L, vdso_data);
> +	pr_info("vdso: %ld pages (%ld code, %ld data)\n",
> +		vdso_pages + 1, vdso_pages, 1L);

It's probably better to drop this pr_info() entirely. The number of data and
code pages hasn't changed since this was upstreamed, and the pointers were the
useful part for debugging.

If you respin this to delete the pr_info() entirely, then feel free to add:

Acked-by: Mark Rutland <mark.rutland@....com>

Mark.