Re: [PATCH 1/7] fs/exec: make __set_task_comm always set a nul terminated string

[David Hildenbrand]

On 08.11.21 09:38, Yafang Shao wrote:
> Make sure the string set to task comm is always nul terminated.
> 

strlcpy: "the result is always a valid NUL-terminated string that fits
in the buffer"

The only difference seems to be that strscpy_pad() pads the remainder
with zeroes.

Is this description correct and I am missing something important?

> Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
> Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
> Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
> Cc: Arnaldo Carvalho de Melo <arnaldo.melo@xxxxxxxxx>
> Cc: Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx>
> Cc: Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx>
> Cc: Michal Miroslaw <mirq-linux@xxxxxxxxxxxx> 
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
> Cc: David Hildenbrand <david@xxxxxxxxxx>
> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> Cc: Petr Mladek <pmladek@xxxxxxxx>
> ---
>  fs/exec.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/exec.c b/fs/exec.c
> index a098c133d8d7..404156b5b314 100644
> --- a/fs/exec.c
> +++ b/fs/exec.c
> @@ -1224,7 +1224,7 @@ void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec)
>  {
>  	task_lock(tsk);
>  	trace_task_rename(tsk, buf);
> -	strlcpy(tsk->comm, buf, sizeof(tsk->comm));
> +	strscpy_pad(tsk->comm, buf, sizeof(tsk->comm));
>  	task_unlock(tsk);
>  	perf_event_comm(tsk, exec);
>  }
> 


-- 
Thanks,

David / dhildenb