linux-kernel - Re: [PATCH] scripts: fix memleak error in read

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Message-Id: <20191022151305.c4af5c45ee7c605b4b12ae32@linux-foundation.org>
Date:   Tue, 22 Oct 2019 15:13:05 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     linfeilong <linfeilong@...wei.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] scripts: fix memleak error in read_file

On Tue, 22 Oct 2019 11:47:59 +0000 linfeilong <linfeilong@...wei.com> wrote:

> An error is found by the static code analysis tool: "memleak"
> Fix this by add free before return.
> 
> Signed-off-by: Feilong Lin <linfeilong@...wei.com>
> ---
>  scripts/insert-sys-cert.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/scripts/insert-sys-cert.c b/scripts/insert-sys-cert.c
> index 8902836..22d99a8 100644
> --- a/scripts/insert-sys-cert.c
> +++ b/scripts/insert-sys-cert.c
> @@ -250,6 +250,7 @@ static char *read_file(char *file_name, int *size)
>  	}
>  	if (read(fd, buf, *size) != *size) {
>  		perror("File read failed");
> +		free(buf);
>  		close(fd);
>  		return NULL;
>  	}

A few lines later we do

	return buf;

so the patch adds a use-after-free error.

We could do a free(cert) down in main() or we could just do nothing -
read_file() is only called a single time.