[PATCH bpf-next RFC v1 1/5] bpf: Implement file local storage
Kumar Kartikeya Dwivedi
memxor at gmail.com
Sat Aug 21 18:48:20 UTC 2021
This map is useful in general to tie data associated with a open file
(not fd) from eBPF programs, such that data is released when the file
goes away (e.g. checkpoint/restore usecase).
Another usecase is implementing Capsicum [0] style capability sandbox in
userspace using eBPF LSM, enforcing rights at the file level using this
mechanism.
The implementation is exactly similar to bpf_inode_storage, with some
minor changes where required.
[0]: https://www.usenix.org/legacy/event/sec10/tech/full_papers/Watson.pdf
Signed-off-by: Kumar Kartikeya Dwivedi <memxor at gmail.com>
---
include/linux/bpf_lsm.h | 21 +++
include/linux/bpf_types.h | 1 +
include/uapi/linux/bpf.h | 39 ++++++
kernel/bpf/Makefile | 2 +-
kernel/bpf/bpf_file_storage.c | 244 ++++++++++++++++++++++++++++++++++
kernel/bpf/bpf_lsm.c | 4 +
kernel/bpf/syscall.c | 3 +-
kernel/bpf/verifier.c | 10 ++
security/bpf/hooks.c | 2 +
9 files changed, 324 insertions(+), 2 deletions(-)
create mode 100644 kernel/bpf/bpf_file_storage.c
diff --git a/include/linux/bpf_lsm.h b/include/linux/bpf_lsm.h
index 479c101546ad..5901a39cd5ac 100644
--- a/include/linux/bpf_lsm.h
+++ b/include/linux/bpf_lsm.h
@@ -42,6 +42,18 @@ extern const struct bpf_func_proto bpf_inode_storage_get_proto;
extern const struct bpf_func_proto bpf_inode_storage_delete_proto;
void bpf_inode_storage_free(struct inode *inode);
+static inline struct bpf_storage_blob *bpf_file(const struct file *file)
+{
+ if (unlikely(!file->f_security))
+ return NULL;
+
+ return file->f_security + bpf_lsm_blob_sizes.lbs_file;
+}
+
+extern const struct bpf_func_proto bpf_file_storage_get_proto;
+extern const struct bpf_func_proto bpf_file_storage_delete_proto;
+void bpf_file_storage_free(struct file *file);
+
#else /* !CONFIG_BPF_LSM */
static inline bool bpf_lsm_is_sleepable_hook(u32 btf_id)
@@ -65,6 +77,15 @@ static inline void bpf_inode_storage_free(struct inode *inode)
{
}
+static inline struct bpf_storage_blob *bpf_file(const struct file *file)
+{
+ return NULL;
+}
+
+static inline void bpf_file_storage_free(struct file *file)
+{
+}
+
#endif /* CONFIG_BPF_LSM */
#endif /* _LINUX_BPF_LSM_H */
diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h
index 9c81724e4b98..c68cc6d9e7da 100644
--- a/include/linux/bpf_types.h
+++ b/include/linux/bpf_types.h
@@ -107,6 +107,7 @@ BPF_MAP_TYPE(BPF_MAP_TYPE_DEVMAP_HASH, dev_map_hash_ops)
BPF_MAP_TYPE(BPF_MAP_TYPE_SK_STORAGE, sk_storage_map_ops)
#ifdef CONFIG_BPF_LSM
BPF_MAP_TYPE(BPF_MAP_TYPE_INODE_STORAGE, inode_storage_map_ops)
+BPF_MAP_TYPE(BPF_MAP_TYPE_FILE_STORAGE, file_storage_map_ops)
#endif
BPF_MAP_TYPE(BPF_MAP_TYPE_TASK_STORAGE, task_storage_map_ops)
BPF_MAP_TYPE(BPF_MAP_TYPE_CPUMAP, cpu_map_ops)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index c4f7892edb2b..d4bf4e4d56b5 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -906,6 +906,7 @@ enum bpf_map_type {
BPF_MAP_TYPE_RINGBUF,
BPF_MAP_TYPE_INODE_STORAGE,
BPF_MAP_TYPE_TASK_STORAGE,
+ BPF_MAP_TYPE_FILE_STORAGE,
};
/* Note that tracing related programs such as
@@ -4871,6 +4872,42 @@ union bpf_attr {
* Return
* Value specified by user at BPF link creation/attachment time
* or 0, if it was not specified.
+ *
+ * void *bpf_file_storage_get(struct bpf_map *map, void *file, void *value, u64 flags)
+ * Description
+ * Get a bpf_local_storage from a *file*.
+ *
+ * Logically, it could be thought of as getting the value from
+ * a *map* with *file* as the **key**. From this
+ * perspective, the usage is not much different from
+ * **bpf_map_lookup_elem**\ (*map*, **&**\ *file*) except this
+ * helper enforces the key must be an file and the map must also
+ * be a **BPF_MAP_TYPE_FILE_STORAGE**.
+ *
+ * Underneath, the value is stored locally at *file* instead of
+ * the *map*. The *map* is used as the bpf-local-storage
+ * "type". The bpf-local-storage "type" (i.e. the *map*) is
+ * searched against all bpf_local_storage residing at *file*.
+ *
+ * An optional *flags* (**BPF_LOCAL_STORAGE_GET_F_CREATE**) can be
+ * used such that a new bpf_local_storage will be
+ * created if one does not exist. *value* can be used
+ * together with **BPF_LOCAL_STORAGE_GET_F_CREATE** to specify
+ * the initial value of a bpf_local_storage. If *value* is
+ * **NULL**, the new bpf_local_storage will be zero initialized.
+ * Return
+ * A bpf_local_storage pointer is returned on success.
+ *
+ * **NULL** if not found or there was an error in adding
+ * a new bpf_local_storage.
+ *
+ * int bpf_file_storage_delete(struct bpf_map *map, void *file)
+ * Description
+ * Delete a bpf_local_storage from a *file*.
+ * Return
+ * 0 on success.
+ *
+ * **-ENOENT** if the bpf_local_storage cannot be found.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -5048,6 +5085,8 @@ union bpf_attr {
FN(timer_cancel), \
FN(get_func_ip), \
FN(get_attach_cookie), \
+ FN(file_storage_get), \
+ FN(file_storage_delete), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile
index 7f33098ca63f..98a18e402a0a 100644
--- a/kernel/bpf/Makefile
+++ b/kernel/bpf/Makefile
@@ -10,7 +10,7 @@ obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o tnum.o bpf_i
obj-$(CONFIG_BPF_SYSCALL) += hashtab.o arraymap.o percpu_freelist.o bpf_lru_list.o lpm_trie.o map_in_map.o
obj-$(CONFIG_BPF_SYSCALL) += local_storage.o queue_stack_maps.o ringbuf.o
obj-$(CONFIG_BPF_SYSCALL) += bpf_local_storage.o bpf_task_storage.o
-obj-${CONFIG_BPF_LSM} += bpf_inode_storage.o
+obj-${CONFIG_BPF_LSM} += bpf_inode_storage.o bpf_file_storage.o
obj-$(CONFIG_BPF_SYSCALL) += disasm.o
obj-$(CONFIG_BPF_JIT) += trampoline.o
obj-$(CONFIG_BPF_SYSCALL) += btf.o
diff --git a/kernel/bpf/bpf_file_storage.c b/kernel/bpf/bpf_file_storage.c
new file mode 100644
index 000000000000..c826bc0405c4
--- /dev/null
+++ b/kernel/bpf/bpf_file_storage.c
@@ -0,0 +1,244 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/rculist.h>
+#include <linux/list.h>
+#include <linux/hash.h>
+#include <linux/types.h>
+#include <linux/filter.h>
+#include <linux/spinlock.h>
+#include <linux/bpf.h>
+#include <linux/bpf_local_storage.h>
+#include <uapi/linux/btf.h>
+#include <linux/bpf_lsm.h>
+#include <linux/btf_ids.h>
+
+DEFINE_BPF_STORAGE_CACHE(file_cache);
+
+static struct bpf_local_storage __rcu **file_storage_ptr(void *owner)
+{
+ struct bpf_storage_blob *bsb;
+ struct file *file = owner;
+
+ bsb = bpf_file(file);
+ if (!bsb)
+ return NULL;
+ return &bsb->storage;
+}
+
+static struct bpf_local_storage_data *
+file_storage_lookup(struct file *file, struct bpf_map *map, bool cacheit_lockit)
+{
+ struct bpf_local_storage *file_storage;
+ struct bpf_local_storage_map *smap;
+ struct bpf_storage_blob *bsb;
+
+ bsb = bpf_file(file);
+ if (!bsb)
+ return NULL;
+
+ file_storage = rcu_dereference(bsb->storage);
+ if (!file_storage)
+ return NULL;
+
+ smap = (struct bpf_local_storage_map *)map;
+ return bpf_local_storage_lookup(file_storage, smap, cacheit_lockit);
+}
+
+void bpf_file_storage_free(struct file *file)
+{
+ struct bpf_local_storage *local_storage;
+ struct bpf_local_storage_elem *selem;
+ bool free_file_storage = false;
+ struct bpf_storage_blob *bsb;
+ struct hlist_node *n;
+
+ bsb = bpf_file(file);
+ if (!bsb)
+ return;
+
+ rcu_read_lock();
+
+ local_storage = rcu_dereference(bsb->storage);
+ if (!local_storage) {
+ rcu_read_unlock();
+ return;
+ }
+
+ raw_spin_lock_bh(&local_storage->lock);
+ hlist_for_each_entry_safe(selem, n, &local_storage->list, snode) {
+ bpf_selem_unlink_map(selem);
+ free_file_storage = bpf_selem_unlink_storage_nolock(local_storage,
+ selem, false);
+ }
+ raw_spin_unlock_bh(&local_storage->lock);
+ rcu_read_unlock();
+
+ if (free_file_storage)
+ kfree_rcu(local_storage, rcu);
+}
+
+static void *bpf_fd_file_storage_lookup_elem(struct bpf_map *map, void *key)
+{
+ struct bpf_local_storage_data *sdata;
+ struct file *file;
+ int fd;
+
+ fd = *(int *)key;
+ file = fget_raw(fd);
+ if (!file)
+ return ERR_PTR(-EBADF);
+
+ sdata = file_storage_lookup(file, map, true);
+ fput(file);
+ return sdata ? sdata->data : NULL;
+}
+
+static int bpf_fd_file_storage_update_elem(struct bpf_map *map, void *key,
+ void *value, u64 map_flags)
+{
+ struct bpf_local_storage_data *sdata;
+ struct file *file;
+ int fd;
+
+ fd = *(int *)key;
+ file = fget_raw(fd);
+ if (!file)
+ return -EBADF;
+ if (!file_storage_ptr(file)) {
+ fput(file);
+ return -EBADF;
+ }
+
+ sdata = bpf_local_storage_update(file,
+ (struct bpf_local_storage_map *)map,
+ value, map_flags);
+ fput(file);
+ return PTR_ERR_OR_ZERO(sdata);
+}
+
+static int file_storage_delete(struct file *file, struct bpf_map *map)
+{
+ struct bpf_local_storage_data *sdata;
+
+ sdata = file_storage_lookup(file, map, false);
+ if (!sdata)
+ return -ENOENT;
+
+ bpf_selem_unlink(SELEM(sdata));
+
+ return 0;
+}
+
+static int bpf_fd_file_storage_delete_elem(struct bpf_map *map, void *key)
+{
+ struct file *file;
+ int fd, err;
+
+ fd = *(int *)key;
+ file = fget_raw(fd);
+ if (!file)
+ return -EBADF;
+
+ err = file_storage_delete(file, map);
+ fput(file);
+ return err;
+}
+
+BPF_CALL_4(bpf_file_storage_get, struct bpf_map *, map, struct file *, file,
+ void *, value, u64, flags)
+{
+ struct bpf_local_storage_data *sdata;
+
+ if (flags & ~(BPF_LOCAL_STORAGE_GET_F_CREATE))
+ return (unsigned long)NULL;
+
+ if (!file || !file_storage_ptr(file))
+ return (unsigned long)NULL;
+
+ sdata = file_storage_lookup(file, map, true);
+ if (sdata)
+ return (unsigned long)sdata->data;
+
+ if (flags & BPF_LOCAL_STORAGE_GET_F_CREATE) {
+ sdata = bpf_local_storage_update(
+ file, (struct bpf_local_storage_map *)map, value,
+ BPF_NOEXIST);
+ return IS_ERR(sdata) ? (unsigned long)NULL :
+ (unsigned long)sdata->data;
+ }
+
+ return (unsigned long)NULL;
+}
+
+BPF_CALL_2(bpf_file_storage_delete, struct bpf_map *, map, struct file *, file)
+{
+ if (!file)
+ return -EINVAL;
+
+ return file_storage_delete(file, map);
+}
+
+static int notsupp_get_next_key(struct bpf_map *map, void *key, void *next_key)
+{
+ return -ENOTSUPP;
+}
+
+static struct bpf_map *file_storage_map_alloc(union bpf_attr *attr)
+{
+ struct bpf_local_storage_map *smap;
+
+ smap = bpf_local_storage_map_alloc(attr);
+ if (IS_ERR(smap))
+ return ERR_CAST(smap);
+
+ smap->cache_idx = bpf_local_storage_cache_idx_get(&file_cache);
+ return &smap->map;
+}
+
+static void file_storage_map_free(struct bpf_map *map)
+{
+ struct bpf_local_storage_map *smap;
+
+ smap = (struct bpf_local_storage_map *)map;
+ bpf_local_storage_cache_idx_free(&file_cache, smap->cache_idx);
+ bpf_local_storage_map_free(smap, NULL);
+}
+
+static int file_storage_map_btf_id;
+
+const struct bpf_map_ops file_storage_map_ops = {
+ .map_meta_equal = bpf_map_meta_equal,
+ .map_alloc_check = bpf_local_storage_map_alloc_check,
+ .map_alloc = file_storage_map_alloc,
+ .map_free = file_storage_map_free,
+ .map_get_next_key = notsupp_get_next_key,
+ .map_lookup_elem = bpf_fd_file_storage_lookup_elem,
+ .map_update_elem = bpf_fd_file_storage_update_elem,
+ .map_delete_elem = bpf_fd_file_storage_delete_elem,
+ .map_check_btf = bpf_local_storage_map_check_btf,
+ .map_btf_name = "bpf_local_storage_map",
+ .map_btf_id = &file_storage_map_btf_id,
+ .map_owner_storage_ptr = file_storage_ptr,
+};
+
+BTF_ID_LIST_SINGLE(bpf_file_storage_btf_ids, struct, file)
+
+const struct bpf_func_proto bpf_file_storage_get_proto = {
+ .func = bpf_file_storage_get,
+ .gpl_only = false,
+ .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL,
+ .arg1_type = ARG_CONST_MAP_PTR,
+ .arg2_type = ARG_PTR_TO_BTF_ID,
+ .arg2_btf_id = &bpf_file_storage_btf_ids[0],
+ .arg3_type = ARG_PTR_TO_MAP_VALUE_OR_NULL,
+ .arg4_type = ARG_ANYTHING,
+};
+
+const struct bpf_func_proto bpf_file_storage_delete_proto = {
+ .func = bpf_file_storage_delete,
+ .gpl_only = false,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_CONST_MAP_PTR,
+ .arg2_type = ARG_PTR_TO_BTF_ID,
+ .arg2_btf_id = &bpf_file_storage_btf_ids[0],
+};
diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c
index 06062370c3b8..48c2022fd958 100644
--- a/kernel/bpf/bpf_lsm.c
+++ b/kernel/bpf/bpf_lsm.c
@@ -121,6 +121,10 @@ bpf_lsm_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
return &bpf_bprm_opts_set_proto;
case BPF_FUNC_ima_inode_hash:
return prog->aux->sleepable ? &bpf_ima_inode_hash_proto : NULL;
+ case BPF_FUNC_file_storage_get:
+ return &bpf_file_storage_get_proto;
+ case BPF_FUNC_file_storage_delete:
+ return &bpf_file_storage_delete_proto;
default:
return tracing_prog_func_proto(func_id, prog);
}
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 4e50c0bfdb7d..946a85945776 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -783,7 +783,8 @@ static int map_check_btf(struct bpf_map *map, const struct btf *btf,
map->map_type != BPF_MAP_TYPE_CGROUP_STORAGE &&
map->map_type != BPF_MAP_TYPE_SK_STORAGE &&
map->map_type != BPF_MAP_TYPE_INODE_STORAGE &&
- map->map_type != BPF_MAP_TYPE_TASK_STORAGE)
+ map->map_type != BPF_MAP_TYPE_TASK_STORAGE &&
+ map->map_type != BPF_MAP_TYPE_FILE_STORAGE)
return -ENOTSUPP;
if (map->spin_lock_off + sizeof(struct bpf_spin_lock) >
map->value_size) {
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index f5a0077c9981..dc615658c92d 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5390,6 +5390,11 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env,
func_id != BPF_FUNC_task_storage_delete)
goto error;
break;
+ case BPF_MAP_TYPE_FILE_STORAGE:
+ if (func_id != BPF_FUNC_file_storage_get &&
+ func_id != BPF_FUNC_file_storage_delete)
+ goto error;
+ break;
default:
break;
}
@@ -5473,6 +5478,11 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env,
if (map->map_type != BPF_MAP_TYPE_TASK_STORAGE)
goto error;
break;
+ case BPF_FUNC_file_storage_get:
+ case BPF_FUNC_file_storage_delete:
+ if (map->map_type != BPF_MAP_TYPE_FILE_STORAGE)
+ goto error;
+ break;
default:
break;
}
diff --git a/security/bpf/hooks.c b/security/bpf/hooks.c
index e5971fa74fd7..faa70467db4d 100644
--- a/security/bpf/hooks.c
+++ b/security/bpf/hooks.c
@@ -13,6 +13,7 @@ static struct security_hook_list bpf_lsm_hooks[] __lsm_ro_after_init = {
#undef LSM_HOOK
LSM_HOOK_INIT(inode_free_security, bpf_inode_storage_free),
LSM_HOOK_INIT(task_free, bpf_task_storage_free),
+ LSM_HOOK_INIT(file_free_security, bpf_file_storage_free),
};
static int __init bpf_lsm_init(void)
@@ -25,6 +26,7 @@ static int __init bpf_lsm_init(void)
struct lsm_blob_sizes bpf_lsm_blob_sizes __lsm_ro_after_init = {
.lbs_inode = sizeof(struct bpf_storage_blob),
.lbs_task = sizeof(struct bpf_storage_blob),
+ .lbs_file = sizeof(struct bpf_storage_blob),
};
DEFINE_LSM(bpf) = {
--
2.33.0
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