linux-kernel - Re: [PATCH] x86/mm/init: Stop printing pgt

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Message-ID: <202002291522.0EDB380@keescook>
Date:   Sat, 29 Feb 2020 15:23:10 -0800
From:   Kees Cook <keescook@...omium.org>
To:     x86@...nel.org
Cc:     Arvind Sankar <nivedita@...m.mit.edu>,
        "Tobin C . Harding" <me@...in.cc>, Tycho Andersen <tycho@...ho.ws>,
        kernel-hardening@...ts.openwall.com,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/mm/init: Stop printing pgt_buf addresses

On Sat, Feb 29, 2020 at 06:11:20PM -0500, Arvind Sankar wrote:
> This currently leaks kernel physical addresses into userspace.
> 
> Signed-off-by: Arvind Sankar <nivedita@...m.mit.edu>

Acked-by: Kees Cook <keescook@...omium.org>

-Kees

> ---
>  arch/x86/mm/init.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
> index e7bb483557c9..dc4711f09cdc 100644
> --- a/arch/x86/mm/init.c
> +++ b/arch/x86/mm/init.c
> @@ -121,8 +121,6 @@ __ref void *alloc_low_pages(unsigned int num)
>  	} else {
>  		pfn = pgt_buf_end;
>  		pgt_buf_end += num;
> -		printk(KERN_DEBUG "BRK [%#010lx, %#010lx] PGTABLE\n",
> -			pfn << PAGE_SHIFT, (pgt_buf_end << PAGE_SHIFT) - 1);
>  	}
>  
>  	for (i = 0; i < num; i++) {
> -- 
> 2.24.1
> 

-- 
Kees Cook