1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright (c) 2019 Facebook
4  * Copyright 2020 Google LLC.
5  */
6 
7 #include <linux/rculist.h>
8 #include <linux/list.h>
9 #include <linux/hash.h>
10 #include <linux/types.h>
11 #include <linux/spinlock.h>
12 #include <linux/bpf.h>
13 #include <linux/bpf_local_storage.h>
14 #include <net/sock.h>
15 #include <uapi/linux/sock_diag.h>
16 #include <uapi/linux/btf.h>
17 #include <linux/bpf_lsm.h>
18 #include <linux/btf_ids.h>
19 #include <linux/fdtable.h>
20 
21 DEFINE_BPF_STORAGE_CACHE(inode_cache);
22 
23 static struct bpf_local_storage __rcu **
24 inode_storage_ptr(void *owner)
25 {
26 	struct inode *inode = owner;
27 	struct bpf_storage_blob *bsb;
28 
29 	bsb = bpf_inode(inode);
30 	if (!bsb)
31 		return NULL;
32 	return &bsb->storage;
33 }
34 
35 static struct bpf_local_storage_data *inode_storage_lookup(struct inode *inode,
36 							   struct bpf_map *map,
37 							   bool cacheit_lockit)
38 {
39 	struct bpf_local_storage *inode_storage;
40 	struct bpf_local_storage_map *smap;
41 	struct bpf_storage_blob *bsb;
42 
43 	bsb = bpf_inode(inode);
44 	if (!bsb)
45 		return NULL;
46 
47 	inode_storage = rcu_dereference(bsb->storage);
48 	if (!inode_storage)
49 		return NULL;
50 
51 	smap = (struct bpf_local_storage_map *)map;
52 	return bpf_local_storage_lookup(inode_storage, smap, cacheit_lockit);
53 }
54 
55 void bpf_inode_storage_free(struct inode *inode)
56 {
57 	struct bpf_local_storage_elem *selem;
58 	struct bpf_local_storage *local_storage;
59 	bool free_inode_storage = false;
60 	struct bpf_storage_blob *bsb;
61 	struct hlist_node *n;
62 
63 	bsb = bpf_inode(inode);
64 	if (!bsb)
65 		return;
66 
67 	rcu_read_lock();
68 
69 	local_storage = rcu_dereference(bsb->storage);
70 	if (!local_storage) {
71 		rcu_read_unlock();
72 		return;
73 	}
74 
75 	/* Neither the bpf_prog nor the bpf-map's syscall
76 	 * could be modifying the local_storage->list now.
77 	 * Thus, no elem can be added-to or deleted-from the
78 	 * local_storage->list by the bpf_prog or by the bpf-map's syscall.
79 	 *
80 	 * It is racing with bpf_local_storage_map_free() alone
81 	 * when unlinking elem from the local_storage->list and
82 	 * the map's bucket->list.
83 	 */
84 	raw_spin_lock_bh(&local_storage->lock);
85 	hlist_for_each_entry_safe(selem, n, &local_storage->list, snode) {
86 		/* Always unlink from map before unlinking from
87 		 * local_storage.
88 		 */
89 		bpf_selem_unlink_map(selem);
90 		free_inode_storage = bpf_selem_unlink_storage_nolock(
91 			local_storage, selem, false);
92 	}
93 	raw_spin_unlock_bh(&local_storage->lock);
94 	rcu_read_unlock();
95 
96 	/* free_inoode_storage should always be true as long as
97 	 * local_storage->list was non-empty.
98 	 */
99 	if (free_inode_storage)
100 		kfree_rcu(local_storage, rcu);
101 }
102 
103 static void *bpf_fd_inode_storage_lookup_elem(struct bpf_map *map, void *key)
104 {
105 	struct bpf_local_storage_data *sdata;
106 	struct file *f;
107 	int fd;
108 
109 	fd = *(int *)key;
110 	f = fget_raw(fd);
111 	if (!f)
112 		return ERR_PTR(-EBADF);
113 
114 	sdata = inode_storage_lookup(f->f_inode, map, true);
115 	fput(f);
116 	return sdata ? sdata->data : NULL;
117 }
118 
119 static int bpf_fd_inode_storage_update_elem(struct bpf_map *map, void *key,
120 					 void *value, u64 map_flags)
121 {
122 	struct bpf_local_storage_data *sdata;
123 	struct file *f;
124 	int fd;
125 
126 	fd = *(int *)key;
127 	f = fget_raw(fd);
128 	if (!f)
129 		return -EBADF;
130 	if (!inode_storage_ptr(f->f_inode)) {
131 		fput(f);
132 		return -EBADF;
133 	}
134 
135 	sdata = bpf_local_storage_update(f->f_inode,
136 					 (struct bpf_local_storage_map *)map,
137 					 value, map_flags);
138 	fput(f);
139 	return PTR_ERR_OR_ZERO(sdata);
140 }
141 
142 static int inode_storage_delete(struct inode *inode, struct bpf_map *map)
143 {
144 	struct bpf_local_storage_data *sdata;
145 
146 	sdata = inode_storage_lookup(inode, map, false);
147 	if (!sdata)
148 		return -ENOENT;
149 
150 	bpf_selem_unlink(SELEM(sdata));
151 
152 	return 0;
153 }
154 
155 static int bpf_fd_inode_storage_delete_elem(struct bpf_map *map, void *key)
156 {
157 	struct file *f;
158 	int fd, err;
159 
160 	fd = *(int *)key;
161 	f = fget_raw(fd);
162 	if (!f)
163 		return -EBADF;
164 
165 	err = inode_storage_delete(f->f_inode, map);
166 	fput(f);
167 	return err;
168 }
169 
170 BPF_CALL_4(bpf_inode_storage_get, struct bpf_map *, map, struct inode *, inode,
171 	   void *, value, u64, flags)
172 {
173 	struct bpf_local_storage_data *sdata;
174 
175 	if (flags & ~(BPF_LOCAL_STORAGE_GET_F_CREATE))
176 		return (unsigned long)NULL;
177 
178 	/* explicitly check that the inode_storage_ptr is not
179 	 * NULL as inode_storage_lookup returns NULL in this case and
180 	 * bpf_local_storage_update expects the owner to have a
181 	 * valid storage pointer.
182 	 */
183 	if (!inode || !inode_storage_ptr(inode))
184 		return (unsigned long)NULL;
185 
186 	sdata = inode_storage_lookup(inode, map, true);
187 	if (sdata)
188 		return (unsigned long)sdata->data;
189 
190 	/* This helper must only called from where the inode is guaranteed
191 	 * to have a refcount and cannot be freed.
192 	 */
193 	if (flags & BPF_LOCAL_STORAGE_GET_F_CREATE) {
194 		sdata = bpf_local_storage_update(
195 			inode, (struct bpf_local_storage_map *)map, value,
196 			BPF_NOEXIST);
197 		return IS_ERR(sdata) ? (unsigned long)NULL :
198 					     (unsigned long)sdata->data;
199 	}
200 
201 	return (unsigned long)NULL;
202 }
203 
204 BPF_CALL_2(bpf_inode_storage_delete,
205 	   struct bpf_map *, map, struct inode *, inode)
206 {
207 	if (!inode)
208 		return -EINVAL;
209 
210 	/* This helper must only called from where the inode is guaranteed
211 	 * to have a refcount and cannot be freed.
212 	 */
213 	return inode_storage_delete(inode, map);
214 }
215 
216 static int notsupp_get_next_key(struct bpf_map *map, void *key,
217 				void *next_key)
218 {
219 	return -ENOTSUPP;
220 }
221 
222 static struct bpf_map *inode_storage_map_alloc(union bpf_attr *attr)
223 {
224 	struct bpf_local_storage_map *smap;
225 
226 	smap = bpf_local_storage_map_alloc(attr);
227 	if (IS_ERR(smap))
228 		return ERR_CAST(smap);
229 
230 	smap->cache_idx = bpf_local_storage_cache_idx_get(&inode_cache);
231 	return &smap->map;
232 }
233 
234 static void inode_storage_map_free(struct bpf_map *map)
235 {
236 	struct bpf_local_storage_map *smap;
237 
238 	smap = (struct bpf_local_storage_map *)map;
239 	bpf_local_storage_cache_idx_free(&inode_cache, smap->cache_idx);
240 	bpf_local_storage_map_free(smap, NULL);
241 }
242 
243 static int inode_storage_map_btf_id;
244 const struct bpf_map_ops inode_storage_map_ops = {
245 	.map_meta_equal = bpf_map_meta_equal,
246 	.map_alloc_check = bpf_local_storage_map_alloc_check,
247 	.map_alloc = inode_storage_map_alloc,
248 	.map_free = inode_storage_map_free,
249 	.map_get_next_key = notsupp_get_next_key,
250 	.map_lookup_elem = bpf_fd_inode_storage_lookup_elem,
251 	.map_update_elem = bpf_fd_inode_storage_update_elem,
252 	.map_delete_elem = bpf_fd_inode_storage_delete_elem,
253 	.map_check_btf = bpf_local_storage_map_check_btf,
254 	.map_btf_name = "bpf_local_storage_map",
255 	.map_btf_id = &inode_storage_map_btf_id,
256 	.map_owner_storage_ptr = inode_storage_ptr,
257 };
258 
259 BTF_ID_LIST_SINGLE(bpf_inode_storage_btf_ids, struct, inode)
260 
261 const struct bpf_func_proto bpf_inode_storage_get_proto = {
262 	.func		= bpf_inode_storage_get,
263 	.gpl_only	= false,
264 	.ret_type	= RET_PTR_TO_MAP_VALUE_OR_NULL,
265 	.arg1_type	= ARG_CONST_MAP_PTR,
266 	.arg2_type	= ARG_PTR_TO_BTF_ID,
267 	.arg2_btf_id	= &bpf_inode_storage_btf_ids[0],
268 	.arg3_type	= ARG_PTR_TO_MAP_VALUE_OR_NULL,
269 	.arg4_type	= ARG_ANYTHING,
270 };
271 
272 const struct bpf_func_proto bpf_inode_storage_delete_proto = {
273 	.func		= bpf_inode_storage_delete,
274 	.gpl_only	= false,
275 	.ret_type	= RET_INTEGER,
276 	.arg1_type	= ARG_CONST_MAP_PTR,
277 	.arg2_type	= ARG_PTR_TO_BTF_ID,
278 	.arg2_btf_id	= &bpf_inode_storage_btf_ids[0],
279 };
280