This commit allows for map operations to be loaded by an lkm, rather than
needing to be baked into the kernel at compile time.
Signed-off-by: Aaron Conole <aconole@xxxxxxxxxx>
---
include/linux/bpf.h | 6 +++++
init/Kconfig | 8 +++++++
kernel/bpf/syscall.c | 57 +++++++++++++++++++++++++++++++++++++++++++-
3 files changed, 70 insertions(+), 1 deletion(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 33014ae73103..bf4531f076ca 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -553,6 +553,7 @@ static inline int bpf_map_attr_numa_node(const union bpf_attr *attr)
struct bpf_prog *bpf_prog_get_type_path(const char *name, enum bpf_prog_type type);
int array_map_alloc_check(union bpf_attr *attr);
+void bpf_map_insert_ops(size_t id, const struct bpf_map_ops *ops);
#else /* !CONFIG_BPF_SYSCALL */
static inline struct bpf_prog *bpf_prog_get(u32 ufd)
@@ -665,6 +666,11 @@ static inline struct bpf_prog *bpf_prog_get_type_path(const char *name,
{
return ERR_PTR(-EOPNOTSUPP);
}
+
+static inline void bpf_map_insert_ops(size_t id,
+ const struct bpf_map_ops *ops)
+{
+}
#endif /* CONFIG_BPF_SYSCALL */
static inline struct bpf_prog *bpf_prog_get_type(u32 ufd,
diff --git a/init/Kconfig b/init/Kconfig
index a4112e95724a..aa4eb98af656 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1489,6 +1489,14 @@ config BPF_JIT_ALWAYS_ON
Enables BPF JIT and removes BPF interpreter to avoid
speculative execution of BPF instructions by the interpreter
+config BPF_LOADABLE_MAPS
+ bool "Allow map types to be loaded with modules"
+ depends on BPF_SYSCALL && MODULES
+ help
+ Enables BPF map types to be provided by loadable modules
+ instead of always compiled in. Maps provided dynamically
+ may only be used by super users.
+
config USERFAULTFD
bool "Enable userfaultfd() system call"
select ANON_INODES
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index cf5040fd5434..fa1db9ab81e1 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -49,6 +49,8 @@ static DEFINE_SPINLOCK(map_idr_lock);
int sysctl_unprivileged_bpf_disabled __read_mostly;
+const struct bpf_map_ops loadable_map = {};
+
static const struct bpf_map_ops * const bpf_map_types[] = {
#define BPF_PROG_TYPE(_id, _ops)
#define BPF_MAP_TYPE(_id, _ops) \
@@ -58,6 +60,15 @@ static const struct bpf_map_ops * const bpf_map_types[] = {
#undef BPF_MAP_TYPE
};
+static const struct bpf_map_ops * bpf_loadable_map_types[] = {
+#define BPF_PROG_TYPE(_id, _ops)
+#define BPF_MAP_TYPE(_id, _ops) \
+ [_id] = NULL,
+#include <linux/bpf_types.h>
+#undef BPF_PROG_TYPE
+#undef BPF_MAP_TYPE
+};
+
/*
* If we're handed a bigger struct than we know of, ensure all the unknown bits
* are 0 - i.e. new user-space does not rely on any kernel feature extensions
@@ -105,6 +116,48 @@ const struct bpf_map_ops bpf_map_offload_ops = {
.map_check_btf = map_check_no_btf,
};
+/*
+ * Fills in the modular ops map, provided that the entry is not already
+ * filled, and that the caller has CAP_SYS_ADMIN. */
+void bpf_map_insert_ops(size_t id, const struct bpf_map_ops *ops)
+{
+#ifdef CONFIG_BPF_LOADABLE_MAPS
+ if (!capable(CAP_SYS_ADMIN))
+ return;
+
+ if (id >= ARRAY_SIZE(bpf_loadable_map_types))
+ return;
+
+ id = array_index_nospec(id, ARRAY_SIZE(bpf_loadable_map_types));
+ if (bpf_loadable_map_types[id] == NULL)
+ bpf_loadable_map_types[id] = ops;
+#endif
+}
+EXPORT_SYMBOL_GPL(bpf_map_insert_ops);
+
+static const struct bpf_map_ops *find_loadable_ops(u32 type)
+{
+ struct user_struct *user = get_current_user();
+ const struct bpf_map_ops *ops = NULL;
+
+ if (user->uid.val)
+ goto done;
+
+#ifdef CONFIG_BPF_LOADABLE_MAPS
+ if (!capable(CAP_SYS_ADMIN))
+ goto done;
+
+ if (type >= ARRAY_SIZE(bpf_loadable_map_types))
+ goto done;
+ type = array_index_nospec(type, ARRAY_SIZE(bpf_loadable_map_types));
+ ops = bpf_loadable_map_types[type];
+#endif
+
+done:
+ free_uid(user);
+ return ops;
+}
+
static struct bpf_map *find_and_alloc_map(union bpf_attr *attr)
{
const struct bpf_map_ops *ops;
@@ -115,7 +168,8 @@ static struct bpf_map *find_and_alloc_map(union bpf_attr *attr)
if (type >= ARRAY_SIZE(bpf_map_types))
return ERR_PTR(-EINVAL);
type = array_index_nospec(type, ARRAY_SIZE(bpf_map_types));
- ops = bpf_map_types[type];
+ ops = (bpf_map_types[type] != &loadable_map) ? bpf_map_types[type] :
+ find_loadable_ops(type);
if (!ops)
return ERR_PTR(-EINVAL);
@@ -180,6 +234,7 @@ int bpf_map_precharge_memlock(u32 pages)
return -EPERM;
return 0;
}
+EXPORT_SYMBOL_GPL(bpf_map_precharge_memlock);
static int bpf_charge_memlock(struct user_struct *user, u32 pages)
{
--
2.19.1
