bpf: align and clean bpf_{map,prog}_get helpers

Add a bpf_map_get() function that we're going to use later on and
align/clean the remaining helpers a bit so that we have them a bit
more consistent:

  - __bpf_map_get() and __bpf_prog_get() that both work on the fd
    struct, check whether the descriptor is eBPF and return the
    pointer to the map/prog stored in the private data.

    Also, we can return f.file->private_data directly, the function
    signature is enough of a documentation already.

  - bpf_map_get() and bpf_prog_get() that both work on u32 user fd,
    call their respective __bpf_map_get()/__bpf_prog_get() variants,
    and take a reference.

Signed-off-by: Daniel Borkmann <[email protected]>
Acked-by: Alexei Starovoitov <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

Author: borkmann

include/linux/bpf.h

@@ -167,7 +167,7 @@ struct bpf_prog *bpf_prog_get(u32 ufd);
 void bpf_prog_put(struct bpf_prog *prog);
 void bpf_prog_put_rcu(struct bpf_prog *prog);
 
-struct bpf_map *bpf_map_get(struct fd f);
+struct bpf_map *__bpf_map_get(struct fd f);
 void bpf_map_put(struct bpf_map *map);
 
 extern int sysctl_unprivileged_bpf_disabled;

kernel/bpf/syscall.c

@@ -162,19 +162,29 @@ static int map_create(union bpf_attr *attr)
 /* if error is returned, fd is released.
  * On success caller should complete fd access with matching fdput()
  */
-struct bpf_map *bpf_map_get(struct fd f)
+struct bpf_map *__bpf_map_get(struct fd f)
 {
-	struct bpf_map *map;
-
 	if (!f.file)
 		return ERR_PTR(-EBADF);
-
 	if (f.file->f_op != &bpf_map_fops) {
 		fdput(f);
 		return ERR_PTR(-EINVAL);
 	}
 
-	map = f.file->private_data;
+	return f.file->private_data;
+}
+
+static struct bpf_map *bpf_map_get(u32 ufd)
+{
+	struct fd f = fdget(ufd);
+	struct bpf_map *map;
+
+	map = __bpf_map_get(f);
+	if (IS_ERR(map))
+		return map;
+
+	atomic_inc(&map->refcnt);
+	fdput(f);
 
 	return map;
 }
@@ -202,7 +212,7 @@ static int map_lookup_elem(union bpf_attr *attr)
 		return -EINVAL;
 
 	f = fdget(ufd);
-	map = bpf_map_get(f);
+	map = __bpf_map_get(f);
 	if (IS_ERR(map))
 		return PTR_ERR(map);
 
@@ -261,7 +271,7 @@ static int map_update_elem(union bpf_attr *attr)
 		return -EINVAL;
 
 	f = fdget(ufd);
-	map = bpf_map_get(f);
+	map = __bpf_map_get(f);
 	if (IS_ERR(map))
 		return PTR_ERR(map);
 
@@ -314,7 +324,7 @@ static int map_delete_elem(union bpf_attr *attr)
 		return -EINVAL;
 
 	f = fdget(ufd);
-	map = bpf_map_get(f);
+	map = __bpf_map_get(f);
 	if (IS_ERR(map))
 		return PTR_ERR(map);
 
@@ -355,7 +365,7 @@ static int map_get_next_key(union bpf_attr *attr)
 		return -EINVAL;
 
 	f = fdget(ufd);
-	map = bpf_map_get(f);
+	map = __bpf_map_get(f);
 	if (IS_ERR(map))
 		return PTR_ERR(map);
 
@@ -549,21 +559,16 @@ static int bpf_prog_new_fd(struct bpf_prog *prog)
 				O_RDWR | O_CLOEXEC);
 }
 
-static struct bpf_prog *get_prog(struct fd f)
+static struct bpf_prog *__bpf_prog_get(struct fd f)
 {
-	struct bpf_prog *prog;
-
 	if (!f.file)
 		return ERR_PTR(-EBADF);
-
 	if (f.file->f_op != &bpf_prog_fops) {
 		fdput(f);
 		return ERR_PTR(-EINVAL);
 	}
 
-	prog = f.file->private_data;
-
-	return prog;
+	return f.file->private_data;
 }
 
 /* called by sockets/tracing/seccomp before attaching program to an event
@@ -574,13 +579,13 @@ struct bpf_prog *bpf_prog_get(u32 ufd)
 	struct fd f = fdget(ufd);
 	struct bpf_prog *prog;
 
-	prog = get_prog(f);
-
+	prog = __bpf_prog_get(f);
 	if (IS_ERR(prog))
 		return prog;
 
 	atomic_inc(&prog->aux->refcnt);
 	fdput(f);
+
 	return prog;
 }
 EXPORT_SYMBOL_GPL(bpf_prog_get);

kernel/bpf/verifier.c

@@ -1989,8 +1989,7 @@ static int replace_map_fd_with_map_ptr(struct verifier_env *env)
 			}
 
 			f = fdget(insn->imm);
-
-			map = bpf_map_get(f);
+			map = __bpf_map_get(f);
 			if (IS_ERR(map)) {
 				verbose("fd %d is not pointing to valid bpf_map\n",
 					insn->imm);