linux-kernel - Re: [PATCH] x86/kaslr: simplify the code in mem_avoid

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20190905133950.GA14840@MiWiFi-R3L-srv>
Date:   Thu, 5 Sep 2019 21:39:50 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Qian Cai <cai@....pw>
Cc:     tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/kaslr: simplify the code in mem_avoid_memmap()

On 08/22/19 at 10:26am, Qian Cai wrote:
> If "i >= MAX_MEMMAP_REGIONS" already when entering mem_avoid_memmap(),
> even without the return statement the loop will not run anyway. The only
> time it needs to set "memmap_too_large = true" in this situation is
> "memmap_too_large" is "false" currently. Hence, the code could be
> simplified.

It seems not improved much. If far more than MAX_MEMMAP_REGIONS 'memmap='
specified, the if condition checking looks more straightforward. Anyway,
it's not simplifying much, in my opinion.

Thanks
Baoquan

> 
> Signed-off-by: Qian Cai <cai@....pw>
> ---
>  arch/x86/boot/compressed/kaslr.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
> index 2e53c056ba20..35c6942fb95b 100644
> --- a/arch/x86/boot/compressed/kaslr.c
> +++ b/arch/x86/boot/compressed/kaslr.c
> @@ -176,9 +176,6 @@ static void mem_avoid_memmap(char *str)
>  {
>  	static int i;
>  
> -	if (i >= MAX_MEMMAP_REGIONS)
> -		return;
> -
>  	while (str && (i < MAX_MEMMAP_REGIONS)) {
>  		int rc;
>  		unsigned long long start, size;
> @@ -206,7 +203,7 @@ static void mem_avoid_memmap(char *str)
>  	}
>  
>  	/* More than 4 memmaps, fail kaslr */
> -	if ((i >= MAX_MEMMAP_REGIONS) && str)
> +	if (i >= MAX_MEMMAP_REGIONS && !memmap_too_large)
>  		memmap_too_large = true;
>  }
>  
> -- 
> 1.8.3.1
>