Messages in this thread | | | From | Linus Torvalds <> | Date | Wed, 14 Jul 2021 12:20:47 -0700 | Subject | Re: [GIT PULL] tracing: Add __string_len() and __assign_str_len() helpers |
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On Tue, Jul 13, 2021 at 2:11 PM Steven Rostedt <rostedt@goodmis.org> wrote: > > Add macros for the TRACE_EVENT() macro that can be used to assign strings > that either need to be truncated, or have no nul terminator, and depends > on a length attribute to assign.
I pulled this, but then I looked at the actual patch, and decided it's not acceptable.
> +#define __assign_str_len(dst, src, len) \ > + strncpy(__get_str(dst), (src) ? (const char *)(src) : "(null)", len); \ > + __get_str(dst)[len] = '\0';
I can see so many problems in the above that it's not even funny.
Maybe all users would end up avoiding the pitfalls, but the above really is disgusting.
And yes, there's a pre-existing multi-statement macro without any grouping, but that's not an excuse for doing more of them, and doing them badly.
And by "badly" I mean - among other things - the questionable NUL termination that *overflows* the size that was specified, but also using strncpy() at all.
Hint: use strscpy instead of re-implementing it badly. If you really want the crazy NUL padding that strncpy does - which I doubt you do - use strscpy_pad(), making it explicit.
Linus
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