bpf: export bpf_map_inc_not_zero

Rename existing bpf_map_inc_not_zero to __bpf_map_inc_not_zero to
indicate that it's caller's responsibility to do proper locking.
Create and export bpf_map_inc_not_zero wrapper that properly
locks map_idr_lock. Will be used in the next commit to
hold a map while cloning a socket.

Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Yonghong Song <yhs@fb.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

1 files changed, 13 insertions, 3 deletions

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 5d141f16f6fa..cf8052b016e7 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -683,8 +683,8 @@ struct bpf_map *bpf_map_get_with_uref(u32 ufd)
 }
 
 /* map_idr_lock should have been held */
-static struct bpf_map *bpf_map_inc_not_zero(struct bpf_map *map,
-                                            bool uref)
+static struct bpf_map *__bpf_map_inc_not_zero(struct bpf_map *map,
+                                              bool uref)
 {
         int refold;
 
@@ -704,6 +704,16 @@ static struct bpf_map *bpf_map_inc_not_zero(struct bpf_map *map,
         return map;
 }
 
+struct bpf_map *bpf_map_inc_not_zero(struct bpf_map *map, bool uref)
+{
+        spin_lock_bh(&map_idr_lock);
+        map = __bpf_map_inc_not_zero(map, uref);
+        spin_unlock_bh(&map_idr_lock);
+
+        return map;
+}
+EXPORT_SYMBOL_GPL(bpf_map_inc_not_zero);
+
 int __weak bpf_stackmap_copy(struct bpf_map *map, void *key, void *value)
 {
         return -ENOTSUPP;
@@ -2177,7 +2187,7 @@ static int bpf_map_get_fd_by_id(const union bpf_attr *attr)
         spin_lock_bh(&map_idr_lock);
         map = idr_find(&map_idr, id);
         if (map)
-                map = bpf_map_inc_not_zero(map, true);
+                map = __bpf_map_inc_not_zero(map, true);
         else
                 map = ERR_PTR(-ENOENT);
         spin_unlock_bh(&map_idr_lock);