bpf: Add file mode configuration into bpf maps

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 <fengc@google.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 1 deletions

diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index 68d866628be0..988c04c91e10 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;
@@ -56,7 +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 ||
+            attr->value_size == 0 ||
+            attr->map_flags & ~ARRAY_CREATE_FLAG_MASK ||
             (percpu && numa_node != NUMA_NO_NODE))
                 return ERR_PTR(-EINVAL);