Similarly to other protected fields which might be in a map value -
bpf_spin_lock and bpf_timer - keep track of existence and offset of
struct rb_node within map value struct. This will allow later patches in
this series to prevent writes to rb_node field.
Allowing bpf programs to modify the rbtree node struct's rb_node field
would allow parent and children node pointers to be changed, which could
corrupt an otherwise-valid rbtree.
Signed-off-by: Dave Marchevsky <davemarchevsky@xxxxxx>
---
include/linux/bpf.h | 6 ++++++
include/linux/btf.h | 1 +
kernel/bpf/btf.c | 21 +++++++++++++++++++++
kernel/bpf/syscall.c | 3 +++
4 files changed, 31 insertions(+)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index a627a02cf8ab..b4a44ffb0d6c 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -215,6 +215,7 @@ struct bpf_map {
int spin_lock_off; /* >=0 valid offset, <0 error */
struct bpf_map_value_off *kptr_off_tab;
int timer_off; /* >=0 valid offset, <0 error */
+ int rb_node_off; /* >=0 valid offset, <0 error */
u32 id;
int numa_node;
u32 btf_key_type_id;
@@ -264,6 +265,11 @@ static inline bool map_value_has_kptrs(const struct bpf_map *map)
return !IS_ERR_OR_NULL(map->kptr_off_tab);
}
+static inline bool map_value_has_rb_node(const struct bpf_map *map)
+{
+ return map->rb_node_off >= 0;
+}
+
static inline void check_and_init_map_value(struct bpf_map *map, void *dst)
{
if (unlikely(map_value_has_spin_lock(map)))
diff --git a/include/linux/btf.h b/include/linux/btf.h
index ad93c2d9cc1c..cbf10b6b4ada 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -154,6 +154,7 @@ bool btf_member_is_reg_int(const struct btf *btf, const struct btf_type *s,
u32 expected_offset, u32 expected_size);
int btf_find_spin_lock(const struct btf *btf, const struct btf_type *t);
int btf_find_timer(const struct btf *btf, const struct btf_type *t);
+int btf_find_rb_node(const struct btf *btf, const struct btf_type *t);
struct bpf_map_value_off *btf_parse_kptrs(const struct btf *btf,
const struct btf_type *t);
bool btf_type_is_void(const struct btf_type *t);
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 903719b89238..f020efad8d9b 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -3195,6 +3195,7 @@ enum btf_field_type {
BTF_FIELD_SPIN_LOCK,
BTF_FIELD_TIMER,
BTF_FIELD_KPTR,
+ BTF_FIELD_RB_NODE,
};
enum {
@@ -3282,6 +3283,7 @@ static int btf_find_struct_field(const struct btf *btf, const struct btf_type *t
switch (field_type) {
case BTF_FIELD_SPIN_LOCK:
case BTF_FIELD_TIMER:
+ case BTF_FIELD_RB_NODE:
ret = btf_find_struct(btf, member_type, off, sz,
idx < info_cnt ? &info[idx] : &tmp);
if (ret < 0)
@@ -3332,6 +3334,7 @@ static int btf_find_datasec_var(const struct btf *btf, const struct btf_type *t,
switch (field_type) {
case BTF_FIELD_SPIN_LOCK:
case BTF_FIELD_TIMER:
+ case BTF_FIELD_RB_NODE:
ret = btf_find_struct(btf, var_type, off, sz,
idx < info_cnt ? &info[idx] : &tmp);
if (ret < 0)
@@ -3374,6 +3377,11 @@ static int btf_find_field(const struct btf *btf, const struct btf_type *t,
sz = sizeof(struct bpf_timer);
align = __alignof__(struct bpf_timer);
break;
+ case BTF_FIELD_RB_NODE:
+ name = "rb_node";
+ sz = sizeof(struct rb_node);
+ align = __alignof__(struct rb_node);
+ break;
case BTF_FIELD_KPTR:
name = NULL;
sz = sizeof(u64);
@@ -3420,6 +3428,19 @@ int btf_find_timer(const struct btf *btf, const struct btf_type *t)
return info.off;
}
+int btf_find_rb_node(const struct btf *btf, const struct btf_type *t)
+{
+ struct btf_field_info info;
+ int ret;
+
+ ret = btf_find_field(btf, t, BTF_FIELD_RB_NODE, &info, 1);
+ if (ret < 0)
+ return ret;
+ if (!ret)
+ return -ENOENT;
+ return info.off;
+}
+
struct bpf_map_value_off *btf_parse_kptrs(const struct btf *btf,
const struct btf_type *t)
{
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 83c7136c5788..3947fbd137af 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1052,6 +1052,8 @@ static int map_check_btf(struct bpf_map *map, const struct btf *btf,
}
}
+ map->rb_node_off = btf_find_rb_node(btf, value_type);
+
if (map->ops->map_check_btf) {
ret = map->ops->map_check_btf(map, btf, key_type, value_type);
if (ret < 0)
@@ -1115,6 +1117,7 @@ static int map_create(union bpf_attr *attr)
map->spin_lock_off = -EINVAL;
map->timer_off = -EINVAL;
+ map->rb_node_off = -EINVAL;
if (attr->btf_key_type_id || attr->btf_value_type_id ||
/* Even the map's value is a kernel's struct,
* the bpf_prog.o must have BTF to begin with
--
2.30.2
