linux-kernel - RE: [PATCH] mm/cma_debug.c: align the name buffer length as struct cma

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Date:   Wed, 20 Jul 2022 10:45:33 +0000
From:   "Kassey Li (QUIC)" <quic_yingangl@...cinc.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        "Kassey Li (QUIC)" <quic_yingangl@...cinc.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Sasha Levin <sashal@...nel.org>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Minchan Kim <minchan@...nel.org>
Subject: RE: [PATCH] mm/cma_debug.c: align the name buffer length as struct
 cma

Hi, Andrew: 

Is it the case that the output is never >16 chars anyway?  If so, we'll be OK.    
>> Yes.  I verified on my device by giving cma.name length l< 16 and >16 both. Result is OK.   I mean > 16 showed correctly with this patch. 
>> without this patch, cma.name > 16, only showed 16 characters. 

Best Regards
Kassey

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-----Original Message-----
From: Andrew Morton <akpm@...ux-foundation.org> 
Sent: Wednesday, July 20, 2022 7:19 AM
To: Kassey Li (QUIC) <quic_yingangl@...cinc.com>
Cc: linux-kernel@...r.kernel.org; Sasha Levin <sashal@...nel.org>; Joonsoo Kim <iamjoonsoo.kim@....com>; Minchan Kim <minchan@...nel.org>
Subject: Re: [PATCH] mm/cma_debug.c: align the name buffer length as struct cma

On Tue, 19 Jul 2022 17:15:54 +0800 Kassey Li <quic_yingangl@...cinc.com> wrote:

> Signed-off-by: Kassey Li <quic_yingangl@...cinc.com>
> ---
>  mm/cma_debug.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/cma_debug.c b/mm/cma_debug.c index 
> 2e7704955f4f..c3ffe253e055 100644
> --- a/mm/cma_debug.c
> +++ b/mm/cma_debug.c
> @@ -163,7 +163,7 @@ DEFINE_DEBUGFS_ATTRIBUTE(cma_alloc_fops, NULL, 
> cma_alloc_write, "%llu\n");  static void cma_debugfs_add_one(struct 
> cma *cma, struct dentry *root_dentry)  {
>  	struct dentry *tmp;
> -	char name[16];
> +	char name[CMA_MAX_NAME];
>  
>  	scnprintf(name, sizeof(name), "cma-%s", cma->name);

Seems logical.  But as CMA_MAX_NAME=64, this could result in alteration of the output: less truncation of the original name.

Is it the case that the output is never >16 chars anyway?  If so, we'll be OK.