Re: [PATCH] scripts: handle BrokenPipeError for python scripts

Masahiro Yamada
2023-01-22T17:59:48Z

On Sun, Jan 15, 2023 at 12:04 PM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> On Fri, Jan 13, 2023 at 7:06 AM Kees Cook <keescook@chromium.org> wrote:
> >
> > On Thu, Jan 12, 2023 at 11:30:06AM +0900, Masahiro Yamada wrote:
> > > def main():
> > > try:
> > > # simulate large output (your code replaces this loop)
> > > for x in range(10000):
> > > print("y")
> > > # flush output here to force SIGPIPE to be triggered
> > > # while inside this try block.
> > > sys.stdout.flush()
> > > except BrokenPipeError:
> > > # Python flushes standard streams on exit; redirect remaining output
> > > # to devnull to avoid another BrokenPipeError at shutdown
> > > devnull = os.open(os.devnull, os.O_WRONLY)
> > > os.dup2(devnull, sys.stdout.fileno())
> > > sys.exit(1) # Python exits with error code 1 on EPIPE
> >
> > I still think this is wrong -- they should not continue piping, and
> > should just die with SIGPIPE. It should simply be:
> >
> > signal(SIGPIPE, SIG_DFL);
> >
> > Nothing else needed. No wasted CPU cycles, shell handling continues as
> > per normal.
>
>
> I prefer try-and-except because it is Python's coding style,
> and we can do something before the exit.
> (for example, clean up temporary files)
>
>
> >
> > > if __name__ == '__main__':
> > > main()
> > >
> > > Do not set SIGPIPE’s disposition to SIG_DFL in order to avoid
> > > BrokenPipeError. Doing that would cause your program to exit
> > > unexpectedly whenever any socket connection is interrupted while
> > > your program is still writing to it.
> >
> > This advise is for socket programs, not command-line tools.
>
>
> I still do not understand what is bad
> about using this for command-line tools.
>
>
> >
> > -Kees
> >
> > --
> > Kees Cook
>
>
>
> --
> Best Regards
> Masahiro Yamada

Applied with the typos fixes.

--
Best Regards
Masahiro Yamada