Re: [PATCH] ftrace: Replaces simple_strtoul in ftrace

Masami Hiramatsu
2023-11-20T05:00:18Z

On Mon, 20 Nov 2023 05:46:13 +0530
Yuran Pereira <yuran.pereira@hotmail.com> wrote:

> The function simple_strtoul performs no error checking in scenarios
> where the input value overflows the intended output variable.
> This results in this function successfully returning, even when the
> output does not match the input string (aka the function returns
> successfully even when the result is wrong).
>
> Or as it was mentioned [1], "...simple_strtol(), simple_strtoll(),
> simple_strtoul(), and simple_strtoull() functions explicitly ignore
> overflows, which may lead to unexpected results in callers."
> Hence, the use of those functions is discouraged.
>
> This patch replaces all uses of the simple_strtoul with the safer
> alternatives kstrtoul and kstruint.
>
> Callers affected:
> - add_rec_by_index
> - set_graph_max_depth_function
>
> Side effects of this patch:
> - Since `fgraph_max_depth` is an `unsigned int`, this patch uses
> kstrtouint instead of kstrtoul to avoid any compiler warnings
> that could originate from calling the latter.
> - This patch ensures that the callers of kstrtou* return accordingly
> when kstrtoul and kstruint fail for some reason.
> In this case, both callers this patch is addressing return 0 on error.
>
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#simple-strtol-simple-strtoll-simple-strtoul-simple-strtoull
>

This looks good to me.

Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Thank you!

> Signed-off-by: Yuran Pereira <yuran.pereira@hotmail.com>
> ---
> kernel/trace/ftrace.c | 7 +++----
> 1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 8de8bec5f366..70217ee97322 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -4233,12 +4233,12 @@ static int
> add_rec_by_index(struct ftrace_hash *hash, struct ftrace_glob *func_g,
> int clear_filter)
> {
> - long index = simple_strtoul(func_g->search, NULL, 0);
> + long index;
> struct ftrace_page *pg;
> struct dyn_ftrace *rec;
>
> /* The index starts at 1 */
> - if (--index < 0)
> + if (kstrtoul(func_g->search, 0, &index) || --index < 0)
> return 0;
>
> do_for_each_ftrace_rec(pg, rec) {
> @@ -5810,9 +5810,8 @@ __setup("ftrace_graph_notrace=", set_graph_notrace_function);
>
> static int __init set_graph_max_depth_function(char *str)
> {
> - if (!str)
> + if (!str || kstrtouint(str, 0, &fgraph_max_depth))
> return 0;
> - fgraph_max_depth = simple_strtoul(str, NULL, 0);
> return 1;
> }
> __setup("ftrace_graph_max_depth=", set_graph_max_depth_function);
> --
> 2.25.1
>

--
Masami Hiramatsu (Google) <mhiramat@kernel.org>