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From: Andrii Nakryiko <andrii@kernel.org>
To: <bpf@vger.kernel.org>, <netdev@vger.kernel.org>,
	<paul@paul-moore.com>, <brauner@kernel.org>
Cc: <linux-fsdevel@vger.kernel.org>,
	<linux-security-module@vger.kernel.org>, <keescook@chromium.org>,
	<kernel-team@meta.com>, <sargun@sargun.me>
Subject: [PATCH bpf-next 1/8] bpf: fail BPF_TOKEN_CREATE if no delegation option was set on BPF FS
Date: Thu, 7 Dec 2023 10:54:36 -0800	[thread overview]
Message-ID: <20231207185443.2297160-2-andrii@kernel.org> (raw)
In-Reply-To: <20231207185443.2297160-1-andrii@kernel.org>

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@kernel.org>
---
 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


  reply	other threads:[~2023-12-07 18:54 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-12-07 18:54 [PATCH bpf-next 0/8] BPF token support in libbpf's BPF object Andrii Nakryiko
2023-12-07 18:54 ` Andrii Nakryiko [this message]
2023-12-08 21:49   ` [PATCH bpf-next 1/8] bpf: fail BPF_TOKEN_CREATE if no delegation option was set on BPF FS Christian Brauner
2023-12-08 22:42     ` Andrii Nakryiko
2023-12-11 21:33   ` John Fastabend
2023-12-07 18:54 ` [PATCH bpf-next 2/8] libbpf: split feature detectors definitions from cached results Andrii Nakryiko
2023-12-11 21:38   ` John Fastabend
2023-12-07 18:54 ` [PATCH bpf-next 3/8] libbpf: further decouple feature checking logic from bpf_object Andrii Nakryiko
2023-12-10 15:31   ` Eduard Zingerman
2023-12-11 18:20     ` Andrii Nakryiko
2023-12-11 21:41   ` John Fastabend
2023-12-11 22:50     ` Andrii Nakryiko
2023-12-07 18:54 ` [PATCH bpf-next 4/8] libbpf: move feature detection code into its own file Andrii Nakryiko
2023-12-11 21:41   ` John Fastabend
2023-12-07 18:54 ` [PATCH bpf-next 5/8] libbpf: wire up token_fd into feature probing logic Andrii Nakryiko
2023-12-11 21:44   ` John Fastabend
2023-12-07 18:54 ` [PATCH bpf-next 6/8] libbpf: wire up BPF token support at BPF object level Andrii Nakryiko
2023-12-11 22:56   ` John Fastabend
2023-12-12  0:05     ` Andrii Nakryiko
2023-12-12  0:26       ` John Fastabend
2023-12-07 18:54 ` [PATCH bpf-next 7/8] selftests/bpf: add BPF object loading tests with explicit token passing Andrii Nakryiko
2023-12-11 22:59   ` John Fastabend
2023-12-07 18:54 ` [PATCH bpf-next 8/8] selftests/bpf: add tests for BPF object load with implicit token Andrii Nakryiko
2023-12-11 23:00   ` John Fastabend
2023-12-10 15:30 ` [PATCH bpf-next 0/8] BPF token support in libbpf's BPF object Eduard Zingerman
2023-12-11 18:21   ` Andrii Nakryiko

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