linux-kernel - Re: [PATCH 1/2] mm: cma: fix the name of CMA areas

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Message-ID: <20200603141256.GA559132@carbon.DHCP.thefacebook.com>
Date:   Wed, 3 Jun 2020 07:12:56 -0700
From:   Roman Gushchin <guro@...com>
To:     Barry Song <song.bao.hua@...ilicon.com>
CC:     <akpm@...ux-foundation.org>, <mike.kravetz@...cle.com>,
        <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <linuxarm@...wei.com>
Subject: Re: [PATCH 1/2] mm: cma: fix the name of CMA areas

On Wed, Jun 03, 2020 at 08:40:24PM +1200, Barry Song wrote:
> if users give a name saved in stack, the current code will generate magic
> pointer.
> if users don't give a name(NULL), kasprintf() will always return NULL as
> we are at the early stage. that means cma_init_reserved_mem() will return
> -ENOMEM if users set name parameter as NULL.
> 
> Cc: Roman Gushchin <guro@...com>
> Signed-off-by: Barry Song <song.bao.hua@...ilicon.com>

Acked-by: Roman Gushchin <guro@...com>

Thanks!

> ---
>  mm/cma.c | 13 ++++++-------
>  mm/cma.h |  4 +++-
>  2 files changed, 9 insertions(+), 8 deletions(-)
> 
> diff --git a/mm/cma.c b/mm/cma.c
> index 0463ad2ce06b..b24151fa2101 100644
> --- a/mm/cma.c
> +++ b/mm/cma.c
> @@ -202,13 +202,12 @@ int __init cma_init_reserved_mem(phys_addr_t base, phys_addr_t size,
>  	 * subsystems (like slab allocator) are available.
>  	 */
>  	cma = &cma_areas[cma_area_count];
> -	if (name) {
> -		cma->name = name;
> -	} else {
> -		cma->name = kasprintf(GFP_KERNEL, "cma%d\n", cma_area_count);
> -		if (!cma->name)
> -			return -ENOMEM;
> -	}
> +
> +	if (name)
> +		snprintf(cma->name, CMA_MAX_NAME, name);
> +	else
> +		snprintf(cma->name, CMA_MAX_NAME,  "cma%d\n", cma_area_count);
> +
>  	cma->base_pfn = PFN_DOWN(base);
>  	cma->count = size >> PAGE_SHIFT;
>  	cma->order_per_bit = order_per_bit;
> diff --git a/mm/cma.h b/mm/cma.h
> index 33c0b517733c..27d3f0e9f68f 100644
> --- a/mm/cma.h
> +++ b/mm/cma.h
> @@ -2,6 +2,8 @@
>  #ifndef __MM_CMA_H__
>  #define __MM_CMA_H__
>  
> +#define CMA_MAX_NAME 64
> +
>  struct cma {
>  	unsigned long   base_pfn;
>  	unsigned long   count;
> @@ -12,7 +14,7 @@ struct cma {
>  	struct hlist_head mem_head;
>  	spinlock_t mem_head_lock;
>  #endif
> -	const char *name;
> +	char name[CMA_MAX_NAME];
>  };
>  
>  extern struct cma cma_areas[MAX_CMA_AREAS];
> -- 
> 2.23.0
> 
> 
>