From: Chenbo Feng <redacted>

Introduce the map read/write flags to the eBPF syscalls that returns the
map fd. The flags is used to set up the file mode when construct a new
file descriptor for bpf maps. To not break the backward capability, the
f_flags is set to O_RDWR if the flag passed by syscall is 0. Otherwise
it should be O_RDONLY or O_WRONLY. When the userspace want to modify or
read the map content, it will check the file mode to see if it is
allowed to make the change.

Signed-off-by: Chenbo Feng <redacted>
Acked-by: Alexei Starovoitov <ast@kernel.org>
---
 include/linux/bpf.h      |  6 ++--
 include/uapi/linux/bpf.h |  6 ++++
 kernel/bpf/arraymap.c    |  7 +++--
 kernel/bpf/devmap.c      |  5 ++-
 kernel/bpf/hashtab.c     |  5 +--
 kernel/bpf/inode.c       | 15 ++++++---
 kernel/bpf/lpm_trie.c    |  3 +-
 kernel/bpf/sockmap.c     |  5 ++-
 kernel/bpf/stackmap.c    |  5 ++-
 kernel/bpf/syscall.c     | 80 +++++++++++++++++++++++++++++++++++++++++++-----
 10 files changed, 114 insertions(+), 23 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index bc7da2ddfcaf..0e9ca2555d7f 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h

@@ -308,11 +308,11 @@ void bpf_map_area_free(void *base);
 
 extern int sysctl_unprivileged_bpf_disabled;
 
-int bpf_map_new_fd(struct bpf_map *map);
+int bpf_map_new_fd(struct bpf_map *map, int flags);
 int bpf_prog_new_fd(struct bpf_prog *prog);
 
 int bpf_obj_pin_user(u32 ufd, const char __user *pathname);
-int bpf_obj_get_user(const char __user *pathname);
+int bpf_obj_get_user(const char __user *pathname, int flags);
 
 int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value);
 int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value);

@@ -331,6 +331,8 @@ int bpf_fd_htab_map_update_elem(struct bpf_map *map, struct file *map_file,
 				void *key, void *value, u64 map_flags);
 int bpf_fd_htab_map_lookup_elem(struct bpf_map *map, void *key, u32 *value);
 
+int bpf_get_file_flag(int flags);
+
 /* memcpy that is used with 8-byte aligned pointers, power-of-8 size and
  * forced to use 'long' read/writes to try to atomically copy long counters.
  * Best-effort only.  No barriers here, since it _will_ race with concurrent

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 6db9e1d679cd..9cb50a228c39 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h

@@ -217,6 +217,10 @@ enum bpf_attach_type {
 
 #define BPF_OBJ_NAME_LEN 16U
 
+/* Flags for accessing BPF object */
+#define BPF_F_RDONLY		(1U << 3)
+#define BPF_F_WRONLY		(1U << 4)
+
 union bpf_attr {
 	struct { /* anonymous struct used by BPF_MAP_CREATE command */
 		__u32	map_type;	/* one of enum bpf_map_type */

@@ -259,6 +263,7 @@ union bpf_attr {
 	struct { /* anonymous struct used by BPF_OBJ_* commands */
 		__aligned_u64	pathname;
 		__u32		bpf_fd;
+		__u32		file_flags;
 	};
 
 	struct { /* anonymous struct used by BPF_PROG_ATTACH/DETACH commands */

@@ -286,6 +291,7 @@ union bpf_attr {
 			__u32		map_id;
 		};
 		__u32		next_id;
+		__u32		open_flags;
 	};
 
 	struct { /* anonymous struct used by BPF_OBJ_GET_INFO_BY_FD */

diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index 68d866628be0..f869e48ef2f6 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c

@@ -19,6 +19,9 @@
 
 #include "map_in_map.h"
 
+#define ARRAY_CREATE_FLAG_MASK \
+	(BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY)
+
 static void bpf_array_free_percpu(struct bpf_array *array)
 {
 	int i;

@@ -56,8 +59,8 @@ static struct bpf_map *array_map_alloc(union bpf_attr *attr)
 
 	/* check sanity of attributes */
 	if (attr->max_entries == 0 || attr->key_size != 4 ||
-	    attr->value_size == 0 || attr->map_flags & ~BPF_F_NUMA_NODE ||
-	    (percpu && numa_node != NUMA_NO_NODE))
+	    attr->value_size == 0 || attr->map_flags &
+	    ~ARRAY_CREATE_FLAG_MASK || (percpu && numa_node != NUMA_NO_NODE))