From: Andrii Nakryiko Date: Wed, 13 Dec 2023 19:08:33 +0000 (-0800) Subject: bpf: fail BPF_TOKEN_CREATE if no delegation option was set on BPF FS X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=f5fdb51fb980077a4c6c78f3f775821f611fb38b;p=linux.git bpf: fail BPF_TOKEN_CREATE if no delegation option was set on BPF FS 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. Acked-by: Christian Brauner Acked-by: John Fastabend Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/r/20231213190842.3844987-2-andrii@kernel.org Signed-off-by: Alexei Starovoitov --- diff --git a/kernel/bpf/token.c b/kernel/bpf/token.c index 17212efcde60b..a86fccd57e2d0 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;