Re: [PATCH v3 2/7] selftests/powerpc: Add ptrace setup_core_pattern() null-terminator

[Andrew Donnellan <ajd@linux.ibm.com>]

On Mon, 2022-11-28 at 15:19 +1100, Benjamin Gray wrote:
> - malloc() does not zero the buffer,
> - fread() does not null-terminate it's output,
> - `cat /proc/sys/kernel/core_pattern | hexdump -C` shows the file is
>   not inherently null-terminated
> 
> So using string operations on the buffer is risky. Explicitly add a
> null
> character to the end to make it safer.
> 
> Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>

Reviewed-by: Andrew Donnellan <ajd@linux.ibm.com>

> ---
>  tools/testing/selftests/powerpc/ptrace/core-pkey.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/powerpc/ptrace/core-pkey.c
> b/tools/testing/selftests/powerpc/ptrace/core-pkey.c
> index bbc05ffc5860..5c82ed9e7c65 100644
> --- a/tools/testing/selftests/powerpc/ptrace/core-pkey.c
> +++ b/tools/testing/selftests/powerpc/ptrace/core-pkey.c
> @@ -383,7 +383,7 @@ static int setup_core_pattern(char
> **core_pattern_, bool *changed_)
>                 goto out;
>         }
>  
> -       ret = fread(core_pattern, 1, PATH_MAX, f);
> +       ret = fread(core_pattern, 1, PATH_MAX - 1, f);
>         fclose(f);
>         if (!ret) {
>                 perror("Error reading core_pattern file");
> @@ -391,6 +391,8 @@ static int setup_core_pattern(char
> **core_pattern_, bool *changed_)
>                 goto out;
>         }
>  
> +       core_pattern[ret] = '\0';
> +
>         /* Check whether we can predict the name of the core file. */
>         if (!strcmp(core_pattern, "core") || !strcmp(core_pattern,
> "core.%p"))
>                 *changed_ = false;

-- 
Andrew Donnellan    OzLabs, ADL Canberra
ajd@linux.ibm.com   IBM Australia Limited