bpf: switch maps to CLASS(fd, ...)

        Calling conventions for __bpf_map_get() would be more convenient
if it left fpdut() on failure to callers.  Makes for simpler logics
in the callers.

	Among other things, the proof of memory safety no longer has to
rely upon file->private_data never being ERR_PTR(...) for bpffs files.
Original calling conventions made it impossible for the caller to tell
whether __bpf_map_get() has returned ERR_PTR(-EINVAL) because it has found
the file not be a bpf map one (in which case it would've done fdput())
or because it found that ERR_PTR(-EINVAL) in file->private_data of a
bpf map file (in which case fdput() would _not_ have been done).

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

3 files changed, 42 insertions, 121 deletions

diff --git a/kernel/bpf/map_in_map.c b/kernel/bpf/map_in_map.c
index b4f18c85d7bc..645bd30bc9a9 100644
--- a/kernel/bpf/map_in_map.c
+++ b/kernel/bpf/map_in_map.c
@@ -11,24 +11,18 @@ struct bpf_map *bpf_map_meta_alloc(int inner_map_ufd)
 {
 	struct bpf_map *inner_map, *inner_map_meta;
 	u32 inner_map_meta_size;
-	struct fd f;
-	int ret;
+	CLASS(fd, f)(inner_map_ufd);
 
-	f = fdget(inner_map_ufd);
 	inner_map = __bpf_map_get(f);
 	if (IS_ERR(inner_map))
 		return inner_map;
 
 	/* Does not support >1 level map-in-map */
-	if (inner_map->inner_map_meta) {
-		ret = -EINVAL;
-		goto put;
-	}
+	if (inner_map->inner_map_meta)
+		return ERR_PTR(-EINVAL);
 
-	if (!inner_map->ops->map_meta_equal) {
-		ret = -ENOTSUPP;
-		goto put;
-	}
+	if (!inner_map->ops->map_meta_equal)
+		return ERR_PTR(-ENOTSUPP);
 
 	inner_map_meta_size = sizeof(*inner_map_meta);
 	/* In some cases verifier needs to access beyond just base map. */
@@ -36,10 +30,8 @@ struct bpf_map *bpf_map_meta_alloc(int inner_map_ufd)
 		inner_map_meta_size = sizeof(struct bpf_array);
 
 	inner_map_meta = kzalloc(inner_map_meta_size, GFP_USER);
-	if (!inner_map_meta) {
-		ret = -ENOMEM;
-		goto put;
-	}
+	if (!inner_map_meta)
+		return ERR_PTR(-ENOMEM);
 
 	inner_map_meta->map_type = inner_map->map_type;
 	inner_map_meta->key_size = inner_map->key_size;
@@ -53,8 +45,9 @@ struct bpf_map *bpf_map_meta_alloc(int inner_map_ufd)
 		 * invalid/empty/valid, but ERR_PTR in case of errors. During
 		 * equality NULL or IS_ERR is equivalent.
 		 */
-		ret = PTR_ERR(inner_map_meta->record);
-		goto free;
+		struct bpf_map *ret = ERR_CAST(inner_map_meta->record);
+		kfree(inner_map_meta);
+		return ret;
 	}
 	/* Note: We must use the same BTF, as we also used btf_record_dup above
 	 * which relies on BTF being same for both maps, as some members like
@@ -77,14 +70,7 @@ struct bpf_map *bpf_map_meta_alloc(int inner_map_ufd)
 		inner_array_meta->elem_size = inner_array->elem_size;
 		inner_map_meta->bypass_spec_v1 = inner_map->bypass_spec_v1;
 	}
-
-	fdput(f);
 	return inner_map_meta;
-free:
-	kfree(inner_map_meta);
-put:
-	fdput(f);
-	return ERR_PTR(ret);
 }
 
 void bpf_map_meta_free(struct bpf_map *map_meta)
@@ -110,9 +96,8 @@ void *bpf_map_fd_get_ptr(struct bpf_map *map,
 			 int ufd)
 {
 	struct bpf_map *inner_map, *inner_map_meta;
-	struct fd f;
+	CLASS(fd, f)(ufd);
 
-	f = fdget(ufd);
 	inner_map = __bpf_map_get(f);
 	if (IS_ERR(inner_map))
 		return inner_map;
@@ -123,7 +108,6 @@ void *bpf_map_fd_get_ptr(struct bpf_map *map,
 	else
 		inner_map = ERR_PTR(-EINVAL);
 
-	fdput(f);
 	return inner_map;
 }
 
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 4909e3f23065..ab0d94f41c48 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1418,21 +1418,6 @@ put_token:
 	return err;
 }
 
-/* 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)
-{
-	if (!fd_file(f))
-		return ERR_PTR(-EBADF);
-	if (fd_file(f)->f_op != &bpf_map_fops) {
-		fdput(f);
-		return ERR_PTR(-EINVAL);
-	}
-
-	return fd_file(f)->private_data;
-}
-
 void bpf_map_inc(struct bpf_map *map)
 {
 	atomic64_inc(&map->refcnt);
@@ -1448,15 +1433,11 @@ EXPORT_SYMBOL_GPL(bpf_map_inc_with_uref);
 
 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;
+	CLASS(fd, f)(ufd);
+	struct bpf_map *map = __bpf_map_get(f);
 
-	bpf_map_inc(map);
-	fdput(f);
+	if (!IS_ERR(map))
+		bpf_map_inc(map);
 
 	return map;
 }
@@ -1464,15 +1445,11 @@ EXPORT_SYMBOL(bpf_map_get);
 
 struct bpf_map *bpf_map_get_with_uref(u32 ufd)
 {
-	struct fd f = fdget(ufd);
-	struct bpf_map *map;
-
-	map = __bpf_map_get(f);
-	if (IS_ERR(map))
-		return map;
+	CLASS(fd, f)(ufd);
+	struct bpf_map *map = __bpf_map_get(f);
 
-	bpf_map_inc_with_uref(map);
-	fdput(f);
+	if (!IS_ERR(map))
+		bpf_map_inc_with_uref(map);
 
 	return map;
 }
@@ -1537,11 +1514,9 @@ static int map_lookup_elem(union bpf_attr *attr)
 {
 	void __user *ukey = u64_to_user_ptr(attr->key);
 	void __user *uvalue = u64_to_user_ptr(attr->value);
-	int ufd = attr->map_fd;
 	struct bpf_map *map;
 	void *key, *value;
 	u32 value_size;
-	struct fd f;
 	int err;
 
 	if (CHECK_ATTR(BPF_MAP_LOOKUP_ELEM))
@@ -1550,26 +1525,20 @@ static int map_lookup_elem(union bpf_attr *attr)
 	if (attr->flags & ~BPF_F_LOCK)
 		return -EINVAL;
 
-	f = fdget(ufd);
+	CLASS(fd, f)(attr->map_fd);
 	map = __bpf_map_get(f);
 	if (IS_ERR(map))
 		return PTR_ERR(map);
-	if (!(map_get_sys_perms(map, f) & FMODE_CAN_READ)) {
-		err = -EPERM;
-		goto err_put;
-	}
+	if (!(map_get_sys_perms(map, f) & FMODE_CAN_READ))
+		return -EPERM;
 
 	if ((attr->flags & BPF_F_LOCK) &&
-	    !btf_record_has_field(map->record, BPF_SPIN_LOCK)) {
-		err = -EINVAL;
-		goto err_put;
-	}
+	    !btf_record_has_field(map->record, BPF_SPIN_LOCK))
+		return -EINVAL;
 
 	key = __bpf_copy_key(ukey, map->key_size);
-	if (IS_ERR(key)) {
-		err = PTR_ERR(key);
-		goto err_put;
-	}
+	if (IS_ERR(key))
+		return PTR_ERR(key);
 
 	value_size = bpf_map_value_size(map);
 
@@ -1600,8 +1569,6 @@ free_value:
 	kvfree(value);
 free_key:
 	kvfree(key);
-err_put:
-	fdput(f);
 	return err;
 }
 
@@ -1612,17 +1579,15 @@ static int map_update_elem(union bpf_attr *attr, bpfptr_t uattr)
 {
 	bpfptr_t ukey = make_bpfptr(attr->key, uattr.is_kernel);
 	bpfptr_t uvalue = make_bpfptr(attr->value, uattr.is_kernel);
-	int ufd = attr->map_fd;
 	struct bpf_map *map;
 	void *key, *value;
 	u32 value_size;
-	struct fd f;
 	int err;
 
 	if (CHECK_ATTR(BPF_MAP_UPDATE_ELEM))
 		return -EINVAL;
 
-	f = fdget(ufd);
+	CLASS(fd, f)(attr->map_fd);
 	map = __bpf_map_get(f);
 	if (IS_ERR(map))
 		return PTR_ERR(map);
@@ -1660,7 +1625,6 @@ free_key:
 	kvfree(key);
 err_put:
 	bpf_map_write_active_dec(map);
-	fdput(f);
 	return err;
 }
 
@@ -1669,16 +1633,14 @@ err_put:
 static int map_delete_elem(union bpf_attr *attr, bpfptr_t uattr)
 {
 	bpfptr_t ukey = make_bpfptr(attr->key, uattr.is_kernel);
-	int ufd = attr->map_fd;
 	struct bpf_map *map;
-	struct fd f;
 	void *key;
 	int err;
 
 	if (CHECK_ATTR(BPF_MAP_DELETE_ELEM))
 		return -EINVAL;
 
-	f = fdget(ufd);
+	CLASS(fd, f)(attr->map_fd);
 	map = __bpf_map_get(f);
 	if (IS_ERR(map))
 		return PTR_ERR(map);
@@ -1715,7 +1677,6 @@ out:
 	kvfree(key);
 err_put:
 	bpf_map_write_active_dec(map);
-	fdput(f);
 	return err;
 }
 
@@ -1726,30 +1687,24 @@ static int map_get_next_key(union bpf_attr *attr)
 {
 	void __user *ukey = u64_to_user_ptr(attr->key);
 	void __user *unext_key = u64_to_user_ptr(attr->next_key);
-	int ufd = attr->map_fd;
 	struct bpf_map *map;
 	void *key, *next_key;
-	struct fd f;
 	int err;
 
 	if (CHECK_ATTR(BPF_MAP_GET_NEXT_KEY))
 		return -EINVAL;
 
-	f = fdget(ufd);
+	CLASS(fd, f)(attr->map_fd);
 	map = __bpf_map_get(f);
 	if (IS_ERR(map))
 		return PTR_ERR(map);
-	if (!(map_get_sys_perms(map, f) & FMODE_CAN_READ)) {
-		err = -EPERM;
-		goto err_put;
-	}
+	if (!(map_get_sys_perms(map, f) & FMODE_CAN_READ))
+		return -EPERM;
 
 	if (ukey) {
 		key = __bpf_copy_key(ukey, map->key_size);
-		if (IS_ERR(key)) {
-			err = PTR_ERR(key);
-			goto err_put;
-		}
+		if (IS_ERR(key))
+			return PTR_ERR(key);
 	} else {
 		key = NULL;
 	}
@@ -1781,8 +1736,6 @@ free_next_key:
 	kvfree(next_key);
 free_key:
 	kvfree(key);
-err_put:
-	fdput(f);
 	return err;
 }
 
@@ -2011,11 +1964,9 @@ static int map_lookup_and_delete_elem(union bpf_attr *attr)
 {
 	void __user *ukey = u64_to_user_ptr(attr->key);
 	void __user *uvalue = u64_to_user_ptr(attr->value);
-	int ufd = attr->map_fd;
 	struct bpf_map *map;
 	void *key, *value;
 	u32 value_size;
-	struct fd f;
 	int err;
 
 	if (CHECK_ATTR(BPF_MAP_LOOKUP_AND_DELETE_ELEM))
@@ -2024,7 +1975,7 @@ static int map_lookup_and_delete_elem(union bpf_attr *attr)
 	if (attr->flags & ~BPF_F_LOCK)
 		return -EINVAL;
 
-	f = fdget(ufd);
+	CLASS(fd, f)(attr->map_fd);
 	map = __bpf_map_get(f);
 	if (IS_ERR(map))
 		return PTR_ERR(map);
@@ -2094,7 +2045,6 @@ free_key:
 	kvfree(key);
 err_put:
 	bpf_map_write_active_dec(map);
-	fdput(f);
 	return err;
 }
 
@@ -2102,27 +2052,22 @@ err_put:
 
 static int map_freeze(const union bpf_attr *attr)
 {
-	int err = 0, ufd = attr->map_fd;
+	int err = 0;
 	struct bpf_map *map;
-	struct fd f;
 
 	if (CHECK_ATTR(BPF_MAP_FREEZE))
 		return -EINVAL;
 
-	f = fdget(ufd);
+	CLASS(fd, f)(attr->map_fd);
 	map = __bpf_map_get(f);
 	if (IS_ERR(map))
 		return PTR_ERR(map);
 
-	if (map->map_type == BPF_MAP_TYPE_STRUCT_OPS || !IS_ERR_OR_NULL(map->record)) {
-		fdput(f);
+	if (map->map_type == BPF_MAP_TYPE_STRUCT_OPS || !IS_ERR_OR_NULL(map->record))
 		return -ENOTSUPP;
-	}
 
-	if (!(map_get_sys_perms(map, f) & FMODE_CAN_WRITE)) {
-		fdput(f);
+	if (!(map_get_sys_perms(map, f) & FMODE_CAN_WRITE))
 		return -EPERM;
-	}
 
 	mutex_lock(&map->freeze_mutex);
 	if (bpf_map_write_active(map)) {
@@ -2137,7 +2082,6 @@ static int map_freeze(const union bpf_attr *attr)
 	WRITE_ONCE(map->frozen, true);
 err_put:
 	mutex_unlock(&map->freeze_mutex);
-	fdput(f);
 	return err;
 }
 
@@ -5175,14 +5119,13 @@ static int bpf_map_do_batch(const union bpf_attr *attr,
 			 cmd == BPF_MAP_LOOKUP_AND_DELETE_BATCH;
 	bool has_write = cmd != BPF_MAP_LOOKUP_BATCH;
 	struct bpf_map *map;
-	int err, ufd;
-	struct fd f;
+	int err;
 
 	if (CHECK_ATTR(BPF_MAP_BATCH))
 		return -EINVAL;
 
-	ufd = attr->batch.map_fd;
-	f = fdget(ufd);
+	CLASS(fd, f)(attr->batch.map_fd);
+
 	map = __bpf_map_get(f);
 	if (IS_ERR(map))
 		return PTR_ERR(map);
@@ -5210,7 +5153,6 @@ err_put:
 		maybe_wait_bpf_programs(map);
 		bpf_map_write_active_dec(map);
 	}
-	fdput(f);
 	return err;
 }
 
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 14e4ef687a59..e3932f8ce10a 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -18872,7 +18872,7 @@ static bool bpf_map_is_cgroup_storage(struct bpf_map *map)
  */
 static int add_used_map_from_fd(struct bpf_verifier_env *env, int fd, bool *reused)
 {
-	struct fd f = fdget(fd);
+	CLASS(fd, f)(fd);
 	struct bpf_map *map;
 	int i;
 
@@ -18886,7 +18886,6 @@ static int add_used_map_from_fd(struct bpf_verifier_env *env, int fd, bool *reus
 	for (i = 0; i < env->used_map_cnt; i++) {
 		if (env->used_maps[i] == map) {
 			*reused = true;
-			fdput(f);
 			return i;
 		}
 	}
@@ -18894,7 +18893,6 @@ static int add_used_map_from_fd(struct bpf_verifier_env *env, int fd, bool *reus
 	if (env->used_map_cnt >= MAX_USED_MAPS) {
 		verbose(env, "The total number of maps per program has reached the limit of %u\n",
 			MAX_USED_MAPS);
-		fdput(f);
 		return -E2BIG;
 	}
 
@@ -18911,10 +18909,7 @@ static int add_used_map_from_fd(struct bpf_verifier_env *env, int fd, bool *reus
 	*reused = false;
 	env->used_maps[env->used_map_cnt++] = map;
 
-	fdput(f);
-
 	return env->used_map_cnt - 1;
-
 }
 
 /* find and rewrite pseudo imm in ld_imm64 instructions: