Re: [PATCH v7 4/8] bpftool: Ensure task comm is always NUL-terminated

[Alejandro Colomar <alx@kernel.org>]

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Hi Yafang,

On Sun, Aug 18, 2024 at 10:27:01AM GMT, Yafang Shao wrote:
> On Sat, Aug 17, 2024 at 4:39 PM Alejandro Colomar <alx@kernel.org> wrote:
> >
> > Hi Yafang,
> >
> > On Sat, Aug 17, 2024 at 10:56:20AM GMT, Yafang Shao wrote:
> > > Let's explicitly ensure the destination string is NUL-terminated. This way,
> > > it won't be affected by changes to the source string.
> > >
> > > Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
> > > Reviewed-by: Quentin Monnet <qmo@kernel.org>
> > > ---
> > >  tools/bpf/bpftool/pids.c | 2 ++
> > >  1 file changed, 2 insertions(+)
> > >
> > > diff --git a/tools/bpf/bpftool/pids.c b/tools/bpf/bpftool/pids.c
> > > index 9b898571b49e..23f488cf1740 100644
> > > --- a/tools/bpf/bpftool/pids.c
> > > +++ b/tools/bpf/bpftool/pids.c
> > > @@ -54,6 +54,7 @@ static void add_ref(struct hashmap *map, struct pid_iter_entry *e)
> > >               ref = &refs->refs[refs->ref_cnt];
> > >               ref->pid = e->pid;
> > >               memcpy(ref->comm, e->comm, sizeof(ref->comm));
> > > +             ref->comm[sizeof(ref->comm) - 1] = '\0';
> >
> > Why doesn't this use strscpy()?
> 
> bpftool is a userspace tool, so strscpy() is only applicable in kernel
> code, correct?

Ahh, makes sense.  LGTM, then.  Maybe the closest user-space function to
strscpy(9) would be strlcpy(3), but I don't know how old of a glibc you
support.  strlcpy(3) is currently in POSIX, and supported by both glibc
and musl, but that's too recent.

Have a lovely day!
Alex

> --
> Regards
> Yafang

-- 
<https://www.alejandro-colomar.es/>

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