netdev - Re: [PATCH v11 bpf-next 02/17] bpf: add BPF token delegation mount options to BPF FS

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Date: Thu, 30 Nov 2023 10:03:48 -0800
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Simon Horman <horms@...nel.org>
Cc: Andrii Nakryiko <andrii@...nel.org>, bpf@...r.kernel.org, netdev@...r.kernel.org, 
	paul@...l-moore.com, brauner@...nel.org, linux-fsdevel@...r.kernel.org, 
	linux-security-module@...r.kernel.org, keescook@...omium.org, 
	kernel-team@...a.com, sargun@...gun.me
Subject: Re: [PATCH v11 bpf-next 02/17] bpf: add BPF token delegation mount
 options to BPF FS

On Thu, Nov 30, 2023 at 8:37 AM Simon Horman <horms@...nel.org> wrote:
>
> On Mon, Nov 27, 2023 at 11:03:54AM -0800, Andrii Nakryiko wrote:
>
> ...
>
> > @@ -764,7 +817,10 @@ static int bpf_get_tree(struct fs_context *fc)
> >
> >  static void bpf_free_fc(struct fs_context *fc)
> >  {
> > -     kfree(fc->fs_private);
> > +     struct bpf_mount_opts *opts = fc->s_fs_info;
> > +
> > +     if (opts)
> > +             kfree(opts);
> >  }
>
> Hi Andrii,
>
> as it looks like there will be a v12, I have a minor nit to report: There
> is no need to check if opts is non-NULL because kfree() is basically a
> no-op if it's argument is NULL.
>
> So perhaps this can become (completely untested!):
>
> static void bpf_free_fc(struct fs_context *fc)
> {
>         kfree(fc->s_fs_info);
> }
>

sure, I can drop the check, I wasn't sure if it's canonical or not to
check the argument for NULL before calling kfree(). For user-space
it's definitely quite expected to not have to check for null before
calling free().


> ...