linux-kernel - Re: [RESEND] tools/mm: Use calloc and check the memory allocation failure

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Message-ID: <09efaf91-4d85-47c9-857f-94f1a9c9bce8@arm.com>
Date: Thu, 12 Sep 2024 09:58:50 +0530
From: Dev Jain <dev.jain@....com>
To: Zhu Jun <zhujun2@...s.chinamobile.com>, akpm@...ux-foundation.org
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [RESEND] tools/mm: Use calloc and check the memory allocation
 failure


On 9/12/24 08:54, Zhu Jun wrote:
> Replace malloc with calloc and add null pointer check
> in case of allocation failure.
>
> Signed-off-by: Zhu Jun <zhujun2@...s.chinamobile.com>
> ---
>   tools/mm/page_owner_sort.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/tools/mm/page_owner_sort.c b/tools/mm/page_owner_sort.c
> index e1f264444342..8c78265cef67 100644
> --- a/tools/mm/page_owner_sort.c
> +++ b/tools/mm/page_owner_sort.c
> @@ -368,9 +368,10 @@ static __u64 get_ts_nsec(char *buf)
>   
>   static char *get_comm(char *buf)
>   {
> -	char *comm_str = malloc(TASK_COMM_LEN);
> +	char *comm_str = calloc(TASK_COMM_LEN, sizeof(char));
>   
> -	memset(comm_str, 0, TASK_COMM_LEN);
> +	if (!comm_str)
> +		return NULL;
>   
>   	search_pattern(&comm_pattern, comm_str, buf);
>   	errno = 0;

Hello Zhu,

It is pointless to resend if you haven't addressed the queries
raised by Andrew. He notes that the callers aren't handling a
possible NULL return, so there is no point in even checking for
a mem alloc failure. I haven't wandered in tools/mm but from a
programming PoV what Andrew says is correct...if you are returning
NULL then you also must decide what to do with that in the caller,
and so on, on which I cannot comment :)