netdev - [PATCH v11 bpf-next 05/17] bpf: add BPF token support to BPF_BTF

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Date: Mon, 27 Nov 2023 11:03:57 -0800
From: Andrii Nakryiko <andrii@...nel.org>
To: <bpf@...r.kernel.org>, <netdev@...r.kernel.org>, <paul@...l-moore.com>,
        <brauner@...nel.org>
CC: <linux-fsdevel@...r.kernel.org>, <linux-security-module@...r.kernel.org>,
        <keescook@...omium.org>, <kernel-team@...a.com>, <sargun@...gun.me>
Subject: [PATCH v11 bpf-next 05/17] bpf: add BPF token support to BPF_BTF_LOAD command

Accept BPF token FD in BPF_BTF_LOAD command to allow BTF data loading
through delegated BPF token. BTF loading is a pretty straightforward
operation, so as long as BPF token is created with allow_cmds granting
BPF_BTF_LOAD command, kernel proceeds to parsing BTF data and creating
BTF object.

Signed-off-by: Andrii Nakryiko <andrii@...nel.org>
---
 include/uapi/linux/bpf.h       |  1 +
 kernel/bpf/syscall.c           | 20 ++++++++++++++++++--
 tools/include/uapi/linux/bpf.h |  1 +
 3 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 5edc3c863519..d870f594c37b 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -1616,6 +1616,7 @@ union bpf_attr {
 		 * truncated), or smaller (if log buffer wasn't filled completely).
 		 */
 		__u32		btf_log_true_size;
+		__u32		btf_token_fd;
 	};
 
 	struct {
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index e004786290dc..a31b19c9a3c8 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -4752,15 +4752,31 @@ static int bpf_obj_get_info_by_fd(const union bpf_attr *attr,
 	return err;
 }
 
-#define BPF_BTF_LOAD_LAST_FIELD btf_log_true_size
+#define BPF_BTF_LOAD_LAST_FIELD btf_token_fd
 
 static int bpf_btf_load(const union bpf_attr *attr, bpfptr_t uattr, __u32 uattr_size)
 {
+	struct bpf_token *token = NULL;
+
 	if (CHECK_ATTR(BPF_BTF_LOAD))
 		return -EINVAL;
 
-	if (!bpf_capable())
+	if (attr->btf_token_fd) {
+		token = bpf_token_get_from_fd(attr->btf_token_fd);
+		if (IS_ERR(token))
+			return PTR_ERR(token);
+		if (!bpf_token_allow_cmd(token, BPF_BTF_LOAD)) {
+			bpf_token_put(token);
+			token = NULL;
+		}
+	}
+
+	if (!bpf_token_capable(token, CAP_BPF)) {
+		bpf_token_put(token);
 		return -EPERM;
+	}
+
+	bpf_token_put(token);
 
 	return btf_new_fd(attr, uattr, uattr_size);
 }
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 5edc3c863519..d870f594c37b 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -1616,6 +1616,7 @@ union bpf_attr {
 		 * truncated), or smaller (if log buffer wasn't filled completely).
 		 */
 		__u32		btf_log_true_size;
+		__u32		btf_token_fd;
 	};
 
 	struct {
-- 
2.34.1