netdev - [PATCH 2/3] security: bpf: Add eBPF LSM hooks and security field to eBPF map

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Date:   Thu, 31 Aug 2017 13:56:34 -0700
From:   Chenbo Feng <chenbofeng.kernel@...il.com>
To:     linux-security-module@...r.kernel.org
Cc:     Jeffrey Vander Stoep <jeffv@...gle.com>, netdev@...r.kernel.org,
        SELinux <Selinux@...ho.nsa.gov>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        lorenzo@...gle.com, Chenbo Feng <fengc@...gle.com>
Subject: [PATCH 2/3] security: bpf: Add eBPF LSM hooks and security field to eBPF map

From: Chenbo Feng <fengc@...gle.com>

Introduce a pointer into struct bpf_map to hold the security information
about the map. The actual security struct varies based on the security
models implemented. Place the LSM hooks before each of the unrestricted
eBPF operations, the map_update_elem and map_delete_elem operations are
checked by security_map_modify. The map_lookup_elem and map_get_next_key
operations are checked by securtiy_map_read.

Signed-off-by: Chenbo Feng <fengc@...gle.com>
---
 include/linux/bpf.h  |  3 +++
 kernel/bpf/syscall.c | 28 ++++++++++++++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index b69e7a5869ff..ca3e6ff7091d 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -53,6 +53,9 @@ struct bpf_map {
 	struct work_struct work;
 	atomic_t usercnt;
 	struct bpf_map *inner_map_meta;
+#ifdef CONFIG_SECURITY
+	void *security;
+#endif
 };
 
 /* function argument constraints */
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 045646da97cc..b15580bcf3b1 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -279,6 +279,10 @@ static int map_create(union bpf_attr *attr)
 	if (err)
 		return -EINVAL;
 
+	err = security_map_create();
+	if (err)
+		return -EACCES;
+
 	/* find map type and init map: hashtable vs rbtree vs bloom vs ... */
 	map = find_and_alloc_map(attr);
 	if (IS_ERR(map))
@@ -291,6 +295,10 @@ static int map_create(union bpf_attr *attr)
 	if (err)
 		goto free_map_nouncharge;
 
+	err = security_post_create(map);
+	if (err < 0)
+		goto free_map;
+
 	err = bpf_map_alloc_id(map);
 	if (err)
 		goto free_map;
@@ -410,6 +418,10 @@ static int map_lookup_elem(union bpf_attr *attr)
 	if (IS_ERR(map))
 		return PTR_ERR(map);
 
+	err = security_map_read(map);
+	if (err)
+		return -EACCES;
+
 	key = memdup_user(ukey, map->key_size);
 	if (IS_ERR(key)) {
 		err = PTR_ERR(key);
@@ -490,6 +502,10 @@ static int map_update_elem(union bpf_attr *attr)
 	if (IS_ERR(map))
 		return PTR_ERR(map);
 
+	err = security_map_modify(map);
+	if (err)
+		return -EACCES;
+
 	key = memdup_user(ukey, map->key_size);
 	if (IS_ERR(key)) {
 		err = PTR_ERR(key);
@@ -573,6 +589,10 @@ static int map_delete_elem(union bpf_attr *attr)
 	if (IS_ERR(map))
 		return PTR_ERR(map);
 
+	err = security_map_modify(map);
+	if (err)
+		return -EACCES;
+
 	key = memdup_user(ukey, map->key_size);
 	if (IS_ERR(key)) {
 		err = PTR_ERR(key);
@@ -616,6 +636,10 @@ static int map_get_next_key(union bpf_attr *attr)
 	if (IS_ERR(map))
 		return PTR_ERR(map);
 
+	err = security_map_read(map);
+	if (err)
+		return -EACCES;
+
 	if (ukey) {
 		key = memdup_user(ukey, map->key_size);
 		if (IS_ERR(key)) {
@@ -935,6 +959,10 @@ static int bpf_prog_load(union bpf_attr *attr)
 	if (CHECK_ATTR(BPF_PROG_LOAD))
 		return -EINVAL;
 
+	err = security_prog_load();
+	if (err)
+		return -EACCES;
+
 	if (attr->prog_flags & ~BPF_F_STRICT_ALIGNMENT)
 		return -EINVAL;
 
-- 
2.14.1.581.gf28d330327-goog