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, 4 insertions, 1 deletions

diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index 135be433e9a0..a15bc636cc98 100644
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -11,6 +11,9 @@
 #include <linux/perf_event.h>
 #include "percpu_freelist.h"
 
+#define STACK_CREATE_FLAG_MASK \
+        (BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY)
+
 struct stack_map_bucket {
         struct pcpu_freelist_node fnode;
         u32 hash;
@@ -60,7 +63,7 @@ static struct bpf_map *stack_map_alloc(union bpf_attr *attr)
         if (!capable(CAP_SYS_ADMIN))
                 return ERR_PTR(-EPERM);
 
-        if (attr->map_flags & ~BPF_F_NUMA_NODE)
+        if (attr->map_flags & ~STACK_CREATE_FLAG_MASK)
                 return ERR_PTR(-EINVAL);
 
         /* check sanity of attributes */