linux-kernel - Re: [PATCH] libbpf: Replace strcpy() with memcpy() in bpf_object_

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Message-ID: <CAO9wTFjZwOcpaSSJJu_khQ=hCdiiQwuVm-=zOAdTr04gbaa45w@mail.gmail.com>
Date: Thu, 17 Jul 2025 22:55:20 +0530
From: Suchit K <suchitkarunakaran@...il.com>
To: Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc: ast@...nel.org, daniel@...earbox.net, andrii@...nel.org, 
	martin.lau@...ux.dev, eddyz87@...il.com, song@...nel.org, 
	yonghong.song@...ux.dev, john.fastabend@...il.com, kpsingh@...nel.org, 
	sdf@...ichev.me, haoluo@...gle.com, jolsa@...nel.org, bpf@...r.kernel.org, 
	skhan@...uxfoundation.org, linux-kernel-mentees@...ts.linux.dev, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] libbpf: Replace strcpy() with memcpy() in bpf_object__new()

On Thu, 17 Jul 2025 at 22:49, Andrii Nakryiko <andrii.nakryiko@...il.com> wrote:
>
> On Thu, Jul 17, 2025 at 4:59 AM Suchit Karunakaran
> <suchitkarunakaran@...il.com> wrote:
> >
> > Replace the unsafe strcpy() call with memcpy() when copying the path
> > into the bpf_object structure. Since the memory is pre-allocated to
> > exactly strlen(path) + 1 bytes and the length is already known, memcpy()
> > is safer than strcpy().
> >
> > Signed-off-by: Suchit Karunakaran <suchitkarunakaran@...il.com>
> > ---
> >  tools/lib/bpf/libbpf.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> > index 52e353368f58..279f226dd965 100644
> > --- a/tools/lib/bpf/libbpf.c
> > +++ b/tools/lib/bpf/libbpf.c
> > @@ -1495,7 +1495,7 @@ static struct bpf_object *bpf_object__new(const char *path,
> >                 return ERR_PTR(-ENOMEM);
> >         }
> >
> > -       strcpy(obj->path, path);
> > +       memcpy(obj->path, path, strlen(path) + 1);
>
>
> This is user-space libbpf code, where the API contract mandates that
> the path argument is a well-formed zero-terminated C string. Plus, if
> you look at the few lines above, we allocate just enough space to fit
> the entire contents of the string without truncation.
>
> In other words, there is nothing to fix or improve here.
>
> pw-bot: cr
>

That makes sense, strcpy() is indeed safe here. Thanks for the clarification.