linux-kernel - Re: [PATCH v2] tracing/eprobe: Replace snprintf with memcpy

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Message-ID: <CAM4UoyqtOBXRD29x_M==KJtnryC87FhTs2tW65AnDxCc7XgY7g@mail.gmail.com>
Date:   Mon, 9 Jan 2023 12:07:26 +0800
From:   Quanfa Fu <quanfafu@...il.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     mhiramat@...nel.org, linux-kernel@...r.kernel.org,
        linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH v2] tracing/eprobe: Replace snprintf with memcpy

Thanks, I'll check it out.
Thanks !!

On Mon, Jan 9, 2023 at 11:52 AM Steven Rostedt <rostedt@...dmis.org> wrote:
>
> On Mon,  9 Jan 2023 11:32:13 +0800
> Quanfa Fu <quanfafu@...il.com> wrote:
>
> > @@ -923,17 +923,17 @@ static int trace_eprobe_parse_filter(struct trace_eprobe *ep, int argc, const ch
> >
> >       p = ep->filter_str;
> >       for (i = 0; i < argc; i++) {
> > -             ret = snprintf(p, len, "%s ", argv[i]);
> > -             if (ret < 0)
> > -                     goto error;
> > -             if (ret > len) {
> > -                     ret = -E2BIG;
> > -                     goto error;
> > -             }
> > -             p += ret;
> > -             len -= ret;
> > +             arg_len = strlen(argv[i]);
> > +             memcpy((void *)p, argv[i], arg_len);
> > +
> > +             if (i == argc - 1)
> > +                     p[arg_len] = '\0';
> > +             else
> > +                     p[arg_len] = ' ';
> > +
> > +             p += arg_len + 1;
> > +             len -= arg_len + 1;
> >       }
>
> The above is too complex. I mentioned strncat() but you could still
> just keep snprintf() too, which adds the '\0';
>
>         for (i = 0; i < argc; i++) {
>                 if (i)
>                         ret = snprintf(p, len, " %s", argv[i]);
>                 else
>                         ret = snprintf(p, len, "%s", argv[i]);
>                 p += ret;
>                 len -= ret;
>         }
>
> -- Steve
>
> > -     p[-1] = '\0';
> >
> >       /*
> >        * Ensure the filter string can be parsed correctly. Note, this