netdev - Re: [PATCH v8 4/8] bpftool: Ensure task comm is always NUL-terminated

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Message-ID: <CALOAHbD0eEOPft2E_RwxrdB0aHC_qV9JGjA2NJvhYeNy1joDRA@mail.gmail.com>
Date: Fri, 13 Sep 2024 10:20:16 +0800
From: Yafang Shao <laoar.shao@...il.com>
To: Justin Stitt <justinstitt@...gle.com>
Cc: akpm@...ux-foundation.org, torvalds@...ux-foundation.org, alx@...nel.org, 
	ebiederm@...ssion.com, alexei.starovoitov@...il.com, rostedt@...dmis.org, 
	catalin.marinas@....com, penguin-kernel@...ove.sakura.ne.jp, 
	linux-mm@...ck.org, linux-fsdevel@...r.kernel.org, 
	linux-trace-kernel@...r.kernel.org, audit@...r.kernel.org, 
	linux-security-module@...r.kernel.org, selinux@...r.kernel.org, 
	bpf@...r.kernel.org, netdev@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
	Quentin Monnet <qmo@...nel.org>
Subject: Re: [PATCH v8 4/8] bpftool: Ensure task comm is always NUL-terminated

On Fri, Sep 13, 2024 at 5:14 AM Justin Stitt <justinstitt@...gle.com> wrote:
>
> Hi,
>
> On Wed, Aug 28, 2024 at 11:03:17AM 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@...il.com>
> > Reviewed-by: Quentin Monnet <qmo@...nel.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';
>
> ...
>
> >               refs->ref_cnt++;
> >
> >               return;
> > @@ -77,6 +78,7 @@ static void add_ref(struct hashmap *map, struct pid_iter_entry *e)
> >       ref = &refs->refs[0];
> >       ref->pid = e->pid;
> >       memcpy(ref->comm, e->comm, sizeof(ref->comm));
> > +     ref->comm[sizeof(ref->comm) - 1] = '\0';
>
> Excuse my ignorance, do we not have a strscpy() equivalent usable in bpf
> code?

To my knowledge, there is no direct equivalent of the standard
strcpy() function available in bpftool or libbpf code.

-- 
Regards
Yafang