bpf: Add BPF_(PROG|MAP)_GET_NEXT_ID command

This patch adds BPF_PROG_GET_NEXT_ID and BPF_MAP_GET_NEXT_ID
to allow userspace to iterate all bpf_prog IDs and bpf_map IDs.

The API is trying to be consistent with the existing
BPF_MAP_GET_NEXT_KEY.

It is currently limited to CAP_SYS_ADMIN which we can
consider to lift it in followup patches.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Alexei Starovoitov <ast@fb.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 38 insertions, 0 deletions

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 4c3075b5d840..2405feedb8c1 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -166,6 +166,7 @@ static void bpf_map_put_uref(struct bpf_map *map)
 void bpf_map_put(struct bpf_map *map)
 {
         if (atomic_dec_and_test(&map->refcnt)) {
+                /* bpf_map_free_id() must be called first */
                 bpf_map_free_id(map);
                 INIT_WORK(&map->work, bpf_map_free_deferred);
                 schedule_work(&map->work);
@@ -726,6 +727,7 @@ void bpf_prog_put(struct bpf_prog *prog)
 {
         if (atomic_dec_and_test(&prog->aux->refcnt)) {
                 trace_bpf_prog_put_rcu(prog);
+                /* bpf_prog_free_id() must be called first */
                 bpf_prog_free_id(prog);
                 bpf_prog_kallsyms_del(prog);
                 call_rcu(&prog->aux->rcu, __bpf_prog_put_rcu);
@@ -1069,6 +1071,34 @@ static int bpf_prog_test_run(const union bpf_attr *attr,
         return ret;
 }
 
+#define BPF_OBJ_GET_NEXT_ID_LAST_FIELD next_id
+
+static int bpf_obj_get_next_id(const union bpf_attr *attr,
+                               union bpf_attr __user *uattr,
+                               struct idr *idr,
+                               spinlock_t *lock)
+{
+        u32 next_id = attr->start_id;
+        int err = 0;
+
+        if (CHECK_ATTR(BPF_OBJ_GET_NEXT_ID) || next_id >= INT_MAX)
+                return -EINVAL;
+
+        if (!capable(CAP_SYS_ADMIN))
+                return -EPERM;
+
+        next_id++;
+        spin_lock_bh(lock);
+        if (!idr_get_next(idr, &next_id))
+                err = -ENOENT;
+        spin_unlock_bh(lock);
+
+        if (!err)
+                err = put_user(next_id, &uattr->next_id);
+
+        return err;
+}
+
 SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, size)
 {
         union bpf_attr attr = {};
@@ -1146,6 +1176,14 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, siz
         case BPF_PROG_TEST_RUN:
                 err = bpf_prog_test_run(&attr, uattr);
                 break;
+        case BPF_PROG_GET_NEXT_ID:
+                err = bpf_obj_get_next_id(&attr, uattr,
+                                          &prog_idr, &prog_idr_lock);
+                break;
+        case BPF_MAP_GET_NEXT_ID:
+                err = bpf_obj_get_next_id(&attr, uattr,
+                                          &map_idr, &map_idr_lock);
+                break;
         default:
                 err = -EINVAL;
                 break;