From: Kui-Feng Lee <thinker.li@xxxxxxxxx>
To ensure that a module remains accessible whenever a struct_ops object of
a struct_ops type provided by the module is still in use.
Signed-off-by: Kui-Feng Lee <thinker.li@xxxxxxxxx>
---
include/linux/bpf.h | 1 +
include/linux/btf.h | 2 +-
kernel/bpf/bpf_struct_ops.c | 70 ++++++++++++++++++++++++++++++-------
3 files changed, 60 insertions(+), 13 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 4f3b67932ded..26feb8a2da4f 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1626,6 +1626,7 @@ struct bpf_struct_ops {
void (*unreg)(void *kdata);
int (*update)(void *kdata, void *old_kdata);
int (*validate)(void *kdata);
+ struct module *owner;
const char *name;
struct btf_func_model func_models[BPF_STRUCT_OPS_MAX_NR_MEMBERS];
};
diff --git a/include/linux/btf.h b/include/linux/btf.h
index 8e37f7eb02c7..6a64b372b7a0 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -575,7 +575,7 @@ struct bpf_struct_ops;
struct bpf_struct_ops_desc;
struct bpf_struct_ops_desc *
-btf_add_struct_ops(struct bpf_struct_ops *st_ops);
+btf_add_struct_ops(struct btf *btf, struct bpf_struct_ops *st_ops);
const struct bpf_struct_ops_desc *
btf_get_struct_ops(struct btf *btf, u32 *ret_cnt);
diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
index 0bc21a39257d..413a3f8b26ba 100644
--- a/kernel/bpf/bpf_struct_ops.c
+++ b/kernel/bpf/bpf_struct_ops.c
@@ -388,6 +388,7 @@ static long bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
const struct btf_member *member;
const struct btf_type *t = st_ops_desc->type;
struct bpf_tramp_links *tlinks;
+ struct module *mod = NULL;
void *udata, *kdata;
int prog_fd, err;
void *image, *image_end;
@@ -425,6 +426,14 @@ static long bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
goto unlock;
}
+ if (st_ops_desc->btf != btf_vmlinux) {
+ mod = btf_try_get_module(st_ops_desc->btf);
+ if (!mod) {
+ err = -EBUSY;
+ goto unlock;
+ }
+ }
+
memcpy(uvalue, value, map->value_size);
udata = &uvalue->data;
@@ -552,6 +561,10 @@ static long bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
* can be seen once BPF_STRUCT_OPS_STATE_INUSE is set.
*/
smp_store_release(&kvalue->state, BPF_STRUCT_OPS_STATE_INUSE);
+ /* Hold the owner module until the struct_ops is
+ * unregistered
+ */
+ mod = NULL;
goto unlock;
}
@@ -568,6 +581,7 @@ static long bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
memset(uvalue, 0, map->value_size);
memset(kvalue, 0, map->value_size);
unlock:
+ module_put(mod);
kfree(tlinks);
mutex_unlock(&st_map->lock);
return err;
@@ -588,6 +602,7 @@ static long bpf_struct_ops_map_delete_elem(struct bpf_map *map, void *key)
switch (prev_state) {
case BPF_STRUCT_OPS_STATE_INUSE:
st_map->st_ops_desc->st_ops->unreg(&st_map->kvalue.data);
+ module_put(st_map->st_ops_desc->st_ops->owner);
bpf_map_put(map);
return 0;
case BPF_STRUCT_OPS_STATE_TOBEFREE:
@@ -674,6 +689,7 @@ static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr)
size_t st_map_size;
struct bpf_struct_ops_map *st_map;
const struct btf_type *t, *vt;
+ struct module *mod = NULL;
struct bpf_map *map;
int ret;
@@ -681,9 +697,17 @@ static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr)
if (!st_ops_desc)
return ERR_PTR(-ENOTSUPP);
+ if (st_ops_desc->btf != btf_vmlinux) {
+ mod = btf_try_get_module(st_ops_desc->btf);
+ if (!mod)
+ return ERR_PTR(-EINVAL);
+ }
+
vt = st_ops_desc->value_type;
- if (attr->value_size != vt->size)
- return ERR_PTR(-EINVAL);
+ if (attr->value_size != vt->size) {
+ ret = -EINVAL;
+ goto errout;
+ }
t = st_ops_desc->type;
@@ -694,17 +718,17 @@ static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr)
(vt->size - sizeof(struct bpf_struct_ops_value));
st_map = bpf_map_area_alloc(st_map_size, NUMA_NO_NODE);
- if (!st_map)
- return ERR_PTR(-ENOMEM);
+ if (!st_map) {
+ ret = -ENOMEM;
+ goto errout;
+ }
st_map->st_ops_desc = st_ops_desc;
map = &st_map->map;
ret = bpf_jit_charge_modmem(PAGE_SIZE);
- if (ret) {
- __bpf_struct_ops_map_free(map);
- return ERR_PTR(ret);
- }
+ if (ret)
+ goto errout_free;
st_map->image = bpf_jit_alloc_exec(PAGE_SIZE);
if (!st_map->image) {
@@ -713,23 +737,32 @@ static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr)
* here.
*/
bpf_jit_uncharge_modmem(PAGE_SIZE);
- __bpf_struct_ops_map_free(map);
- return ERR_PTR(-ENOMEM);
+ ret = -ENOMEM;
+ goto errout_free;
}
st_map->uvalue = bpf_map_area_alloc(vt->size, NUMA_NO_NODE);
st_map->links =
bpf_map_area_alloc(btf_type_vlen(t) * sizeof(struct bpf_links *),
NUMA_NO_NODE);
if (!st_map->uvalue || !st_map->links) {
- __bpf_struct_ops_map_free(map);
- return ERR_PTR(-ENOMEM);
+ ret = -ENOMEM;
+ goto errout_free;
}
mutex_init(&st_map->lock);
set_vm_flush_reset_perms(st_map->image);
bpf_map_init_from_attr(map, attr);
+ module_put(mod);
+
return map;
+
+errout_free:
+ __bpf_struct_ops_map_free(map);
+ btf = NULL; /* has been released */
+errout:
+ module_put(mod);
+ return ERR_PTR(ret);
}
static u64 bpf_struct_ops_map_mem_usage(const struct bpf_map *map)
@@ -811,6 +844,7 @@ static void bpf_struct_ops_map_link_dealloc(struct bpf_link *link)
* bpf_struct_ops_link_create() fails to register.
*/
st_map->st_ops_desc->st_ops->unreg(&st_map->kvalue.data);
+ module_put(st_map->st_ops_desc->st_ops->owner);
bpf_map_put(&st_map->map);
}
kfree(st_link);
@@ -857,6 +891,10 @@ static int bpf_struct_ops_map_link_update(struct bpf_link *link, struct bpf_map
if (!bpf_struct_ops_valid_to_reg(new_map))
return -EINVAL;
+ /* The old map is holding the refcount for the owner module. The
+ * ownership of the owner module refcount is going to be
+ * transferred from the old map to the new map.
+ */
if (!st_map->st_ops_desc->st_ops->update)
return -EOPNOTSUPP;
@@ -902,6 +940,7 @@ int bpf_struct_ops_link_create(union bpf_attr *attr)
struct bpf_link_primer link_primer;
struct bpf_struct_ops_map *st_map;
struct bpf_map *map;
+ struct btf *btf;
int err;
map = bpf_map_get(attr->link_create.map_fd);
@@ -926,8 +965,15 @@ int bpf_struct_ops_link_create(union bpf_attr *attr)
if (err)
goto err_out;
+ /* Hold the owner module until the struct_ops is unregistered. */
+ btf = st_map->st_ops_desc->btf;
+ if (btf != btf_vmlinux && !btf_try_get_module(btf)) {
+ err = -EINVAL;
+ goto err_out;
+ }
err = st_map->st_ops_desc->st_ops->reg(st_map->kvalue.data);
if (err) {
+ module_put(st_map->st_ops_desc->st_ops->owner);
bpf_link_cleanup(&link_primer);
link = NULL;
goto err_out;
--
2.34.1
