Andrii Nakryiko wrote:
> It's quite confusing in practice when it's possible to successfully
> create a BPF token from BPF FS that didn't have any of delegate_xxx
> mount options set up. While it's not wrong, it's actually more
> meaningful to reject BPF_TOKEN_CREATE with specific error code (-ENOENT)
> to let user-space know that no token delegation is setup up.
>
> So, instead of creating empty BPF token that will be always ignored
> because it doesn't have any of the allow_xxx bits set, reject it with
> -ENOENT. If we ever need empty BPF token to be possible, we can support
> that with extra flag passed into BPF_TOKEN_CREATE.
>
> Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
> ---
> kernel/bpf/token.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/bpf/token.c b/kernel/bpf/token.c
> index 17212efcde60..a86fccd57e2d 100644
> --- a/kernel/bpf/token.c
> +++ b/kernel/bpf/token.c
> @@ -152,6 +152,15 @@ int bpf_token_create(union bpf_attr *attr)
> goto out_path;
> }
>
> + mnt_opts = path.dentry->d_sb->s_fs_info;
> + if (mnt_opts->delegate_cmds == 0 &&
> + mnt_opts->delegate_maps == 0 &&
> + mnt_opts->delegate_progs == 0 &&
> + mnt_opts->delegate_attachs == 0) {
> + err = -ENOENT; /* no BPF token delegation is set up */
> + goto out_path;
> + }
> +
> mode = S_IFREG | ((S_IRUSR | S_IWUSR) & ~current_umask());
> inode = bpf_get_inode(path.mnt->mnt_sb, NULL, mode);
> if (IS_ERR(inode)) {
> @@ -181,7 +190,6 @@ int bpf_token_create(union bpf_attr *attr)
> /* remember bpffs owning userns for future ns_capable() checks */
> token->userns = get_user_ns(userns);
>
> - mnt_opts = path.dentry->d_sb->s_fs_info;
> token->allowed_cmds = mnt_opts->delegate_cmds;
> token->allowed_maps = mnt_opts->delegate_maps;
> token->allowed_progs = mnt_opts->delegate_progs;
> --
> 2.34.1
>
>
Acked-by: John Fastabend <john.fastabend@xxxxxxxxx>
