bpf: Introduce bpf_map ID

This patch generates an unique ID for each created bpf_map.
The approach is similar to the earlier patch for bpf_prog ID.

It is worth to note that the bpf_map's ID and bpf_prog's ID
are in two independent ID spaces and both have the same valid range:
[1, INT_MAX).

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>

2 files changed, 34 insertions, 1 deletions

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index c5946d19f2ca..c32bace66d3d 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -46,6 +46,7 @@ struct bpf_map {
         u32 max_entries;
         u32 map_flags;
         u32 pages;
+        u32 id;
         struct user_struct *user;
         const struct bpf_map_ops *ops;
         struct work_struct work;
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 2a1b32b470f1..4c3075b5d840 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -27,6 +27,8 @@
 DEFINE_PER_CPU(int, bpf_prog_active);
 static DEFINE_IDR(prog_idr);
 static DEFINE_SPINLOCK(prog_idr_lock);
+static DEFINE_IDR(map_idr);
+static DEFINE_SPINLOCK(map_idr_lock);
 
 int sysctl_unprivileged_bpf_disabled __read_mostly;
 
@@ -117,6 +119,29 @@ static void bpf_map_uncharge_memlock(struct bpf_map *map)
         free_uid(user);
 }
 
+static int bpf_map_alloc_id(struct bpf_map *map)
+{
+        int id;
+
+        spin_lock_bh(&map_idr_lock);
+        id = idr_alloc_cyclic(&map_idr, map, 1, INT_MAX, GFP_ATOMIC);
+        if (id > 0)
+                map->id = id;
+        spin_unlock_bh(&map_idr_lock);
+
+        if (WARN_ON_ONCE(!id))
+                return -ENOSPC;
+
+        return id > 0 ? 0 : id;
+}
+
+static void bpf_map_free_id(struct bpf_map *map)
+{
+        spin_lock_bh(&map_idr_lock);
+        idr_remove(&map_idr, map->id);
+        spin_unlock_bh(&map_idr_lock);
+}
+
 /* called from workqueue */
 static void bpf_map_free_deferred(struct work_struct *work)
 {
@@ -141,6 +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(map);
                 INIT_WORK(&map->work, bpf_map_free_deferred);
                 schedule_work(&map->work);
         }
@@ -239,14 +265,20 @@ static int map_create(union bpf_attr *attr)
         if (err)
                 goto free_map_nouncharge;
 
+        err = bpf_map_alloc_id(map);
+        if (err)
+                goto free_map;
+
         err = bpf_map_new_fd(map);
         if (err < 0)
                 /* failed to allocate fd */
-                goto free_map;
+                goto free_id;
 
         trace_bpf_map_create(map, err);
         return err;
 
+free_id:
+        bpf_map_free_id(map);
 free_map:
         bpf_map_uncharge_memlock(map);
 free_map_nouncharge: