Hi,
On Mon, Aug 12, 2024 at 10:29:31AM GMT, Yafang Shao wrote:
> Using strscpy() to read the task comm ensures that the name is
> always NUL-terminated, regardless of the source string. This approach also
> facilitates future extensions to the task comm.
Thanks for sending patches replacing str{n}cpy's!
I believe there's at least two more instances of strncpy in trace.c as
well as in trace_events_hist.c (for a grand total of 6 instances in the
files you've touched in this specific patch).
It'd be great if you could replace those instances in this patch as well :>)
This would help greatly with [1].
>
> Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
> Acked-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
> Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
> ---
> kernel/trace/trace.c | 2 +-
> kernel/trace/trace_events_hist.c | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 578a49ff5c32..1b2577f9d734 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -1907,7 +1907,7 @@ __update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu)
> max_data->critical_start = data->critical_start;
> max_data->critical_end = data->critical_end;
>
> - strncpy(max_data->comm, tsk->comm, TASK_COMM_LEN);
> + strscpy(max_data->comm, tsk->comm, TASK_COMM_LEN);
If max_data->comm wants to be NUL-terminated then this is the right
replacement. Without knowing how the trace stack works at all, it's hard
for me to tell if that is the case.
There's a length-supplied format specifier for which this comm field is
used with; Either this is just another safeguard against spilling over
the buffer or this field really doesn't care about NUL-termination.
| seq_printf(m, "# | task: %.16s-%d "
| "(uid:%d nice:%ld policy:%ld rt_prio:%ld)\n",
| data->comm, data->pid,
In the event this field doesn't need to be NUL-terminated then we are
introducing an off-by-one error where we are copying one less useful
byte with strscpy -- Linus pointed out earlier [2] that these things all
just want to be c-strings so this is probably the right change :>)
> max_data->pid = tsk->pid;
> /*
> * If tsk == current, then use current_uid(), as that does not use
> diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> index 6ece1308d36a..4cd24c25ce05 100644
> --- a/kernel/trace/trace_events_hist.c
> +++ b/kernel/trace/trace_events_hist.c
> @@ -1599,7 +1599,7 @@ static inline void save_comm(char *comm, struct task_struct *task)
> return;
> }
>
> - strncpy(comm, task->comm, TASK_COMM_LEN);
> + strscpy(comm, task->comm, TASK_COMM_LEN);
> }
>
> static void hist_elt_data_free(struct hist_elt_data *elt_data)
> --
> 2.43.5
>
Link: https://github.com/KSPP/linux/issues/90 [1]
Link: https://lore.kernel.org/all/CAHk-=whWtUC-AjmGJveAETKOMeMFSTwKwu99v7+b6AyHMmaDFA@xxxxxxxxxxxxxx/ [2]
Thanks
Justin
