bpf: Add BPF token support to BPF_PROG_LOAD command

Add basic support of BPF token to BPF_PROG_LOAD. BPF_F_TOKEN_FD flag
should be set in prog_flags field when providing prog_token_fd.

Wire through a set of allowed BPF program types and attach types,
derived from BPF FS at BPF token creation time. Then make sure we
perform bpf_token_capable() checks everywhere where it's relevant.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20240124022127.2379740-7-andrii@kernel.org

1 files changed, 65 insertions, 25 deletions

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 45b3a55896eb..61b4bf4cc287 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2626,13 +2626,15 @@ static bool is_perfmon_prog_type(enum bpf_prog_type prog_type)
 }
 
 /* last field in 'union bpf_attr' used by this command */
-#define	BPF_PROG_LOAD_LAST_FIELD log_true_size
+#define BPF_PROG_LOAD_LAST_FIELD prog_token_fd
 
 static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
 {
 	enum bpf_prog_type type = attr->prog_type;
 	struct bpf_prog *prog, *dst_prog = NULL;
 	struct btf *attach_btf = NULL;
+	struct bpf_token *token = NULL;
+	bool bpf_cap;
 	int err;
 	char license[128];
 
@@ -2646,13 +2648,35 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
 				 BPF_F_TEST_RND_HI32 |
 				 BPF_F_XDP_HAS_FRAGS |
 				 BPF_F_XDP_DEV_BOUND_ONLY |
-				 BPF_F_TEST_REG_INVARIANTS))
+				 BPF_F_TEST_REG_INVARIANTS |
+				 BPF_F_TOKEN_FD))
 		return -EINVAL;
 
+	bpf_prog_load_fixup_attach_type(attr);
+
+	if (attr->prog_flags & BPF_F_TOKEN_FD) {
+		token = bpf_token_get_from_fd(attr->prog_token_fd);
+		if (IS_ERR(token))
+			return PTR_ERR(token);
+		/* if current token doesn't grant prog loading permissions,
+		 * then we can't use this token, so ignore it and rely on
+		 * system-wide capabilities checks
+		 */
+		if (!bpf_token_allow_cmd(token, BPF_PROG_LOAD) ||
+		    !bpf_token_allow_prog_type(token, attr->prog_type,
+					       attr->expected_attach_type)) {
+			bpf_token_put(token);
+			token = NULL;
+		}
+	}
+
+	bpf_cap = bpf_token_capable(token, CAP_BPF);
+	err = -EPERM;
+
 	if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) &&
 	    (attr->prog_flags & BPF_F_ANY_ALIGNMENT) &&
-	    !bpf_capable())
-		return -EPERM;
+	    !bpf_cap)
+		goto put_token;
 
 	/* Intent here is for unprivileged_bpf_disabled to block BPF program
 	 * creation for unprivileged users; other actions depend
@@ -2661,21 +2685,23 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
 	 * capability checks are still carried out for these
 	 * and other operations.
 	 */
-	if (sysctl_unprivileged_bpf_disabled && !bpf_capable())
-		return -EPERM;
+	if (sysctl_unprivileged_bpf_disabled && !bpf_cap)
+		goto put_token;
 
 	if (attr->insn_cnt == 0 ||
-	    attr->insn_cnt > (bpf_capable() ? BPF_COMPLEXITY_LIMIT_INSNS : BPF_MAXINSNS))
-		return -E2BIG;
+	    attr->insn_cnt > (bpf_cap ? BPF_COMPLEXITY_LIMIT_INSNS : BPF_MAXINSNS)) {
+		err = -E2BIG;
+		goto put_token;
+	}
 	if (type != BPF_PROG_TYPE_SOCKET_FILTER &&
 	    type != BPF_PROG_TYPE_CGROUP_SKB &&
-	    !bpf_capable())
-		return -EPERM;
+	    !bpf_cap)
+		goto put_token;
 
-	if (is_net_admin_prog_type(type) && !bpf_net_capable())
-		return -EPERM;
-	if (is_perfmon_prog_type(type) && !perfmon_capable())
-		return -EPERM;
+	if (is_net_admin_prog_type(type) && !bpf_token_capable(token, CAP_NET_ADMIN))
+		goto put_token;
+	if (is_perfmon_prog_type(type) && !bpf_token_capable(token, CAP_PERFMON))
+		goto put_token;
 
 	/* attach_prog_fd/attach_btf_obj_fd can specify fd of either bpf_prog
 	 * or btf, we need to check which one it is
@@ -2685,27 +2711,33 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
 		if (IS_ERR(dst_prog)) {
 			dst_prog = NULL;
 			attach_btf = btf_get_by_fd(attr->attach_btf_obj_fd);
-			if (IS_ERR(attach_btf))
-				return -EINVAL;
+			if (IS_ERR(attach_btf)) {
+				err = -EINVAL;
+				goto put_token;
+			}
 			if (!btf_is_kernel(attach_btf)) {
 				/* attaching through specifying bpf_prog's BTF
 				 * objects directly might be supported eventually
 				 */
 				btf_put(attach_btf);
-				return -ENOTSUPP;
+				err = -ENOTSUPP;
+				goto put_token;
 			}
 		}
 	} else if (attr->attach_btf_id) {
 		/* fall back to vmlinux BTF, if BTF type ID is specified */
 		attach_btf = bpf_get_btf_vmlinux();
-		if (IS_ERR(attach_btf))
-			return PTR_ERR(attach_btf);
-		if (!attach_btf)
-			return -EINVAL;
+		if (IS_ERR(attach_btf)) {
+			err = PTR_ERR(attach_btf);
+			goto put_token;
+		}
+		if (!attach_btf) {
+			err = -EINVAL;
+			goto put_token;
+		}
 		btf_get(attach_btf);
 	}
 
-	bpf_prog_load_fixup_attach_type(attr);
 	if (bpf_prog_load_check_attach(type, attr->expected_attach_type,
 				       attach_btf, attr->attach_btf_id,
 				       dst_prog)) {
@@ -2713,7 +2745,8 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
 			bpf_prog_put(dst_prog);
 		if (attach_btf)
 			btf_put(attach_btf);
-		return -EINVAL;
+		err = -EINVAL;
+		goto put_token;
 	}
 
 	/* plain bpf_prog allocation */
@@ -2723,7 +2756,8 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
 			bpf_prog_put(dst_prog);
 		if (attach_btf)
 			btf_put(attach_btf);
-		return -ENOMEM;
+		err = -EINVAL;
+		goto put_token;
 	}
 
 	prog->expected_attach_type = attr->expected_attach_type;
@@ -2734,6 +2768,10 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
 	prog->aux->sleepable = attr->prog_flags & BPF_F_SLEEPABLE;
 	prog->aux->xdp_has_frags = attr->prog_flags & BPF_F_XDP_HAS_FRAGS;
 
+	/* move token into prog->aux, reuse taken refcnt */
+	prog->aux->token = token;
+	token = NULL;
+
 	err = security_bpf_prog_alloc(prog->aux);
 	if (err)
 		goto free_prog;
@@ -2851,6 +2889,8 @@ free_prog:
 	if (prog->aux->attach_btf)
 		btf_put(prog->aux->attach_btf);
 	bpf_prog_free(prog);
+put_token:
+	bpf_token_put(token);
 	return err;
 }
 
@@ -3858,7 +3898,7 @@ static int bpf_prog_attach_check_attach_type(const struct bpf_prog *prog,
 	case BPF_PROG_TYPE_SK_LOOKUP:
 		return attach_type == prog->expected_attach_type ? 0 : -EINVAL;
 	case BPF_PROG_TYPE_CGROUP_SKB:
-		if (!bpf_net_capable())
+		if (!bpf_token_capable(prog->aux->token, CAP_NET_ADMIN))
 			/* cg-skb progs can be loaded by unpriv user.
 			 * check permissions at attach time.
 			 */