On 7/22/22 11:34 AM, Dave Marchevsky wrote:
+
+static struct rb_node *rbtree_map_alloc_node(struct bpf_map *map, size_t sz)
+{
+ struct rb_node *node;
+
+ node = bpf_map_kmalloc_node(map, sz, GFP_KERNEL, map->numa_node);
As Yonghong pointed out this should be GFP_NOWAIT for now.
Later we can convert this to bpf_mem_alloc to make sure it's safe from
any context.
+ if (!node)
+ return NULL;
+ RB_CLEAR_NODE(node);
+ return node;
+}
+
+BPF_CALL_2(bpf_rbtree_alloc_node, struct bpf_map *, map, u32, sz)
+{
+ struct rb_node *node;
+
+ if (map->map_type != BPF_MAP_TYPE_RBTREE)
+ return (u64)NULL;
+
+ if (sz < sizeof(*node))
+ return (u64)NULL;
+
+ node = rbtree_map_alloc_node(map, (size_t)sz);
+ if (!node)
+ return (u64)NULL;
+
+ return (u64)node;
+}
+
+const struct bpf_func_proto bpf_rbtree_alloc_node_proto = {
+ .func = bpf_rbtree_alloc_node,
+ .gpl_only = true,
+ .ret_type = RET_PTR_TO_BTF_ID_OR_NULL,
+ .ret_btf_id = &bpf_rbtree_btf_ids[0],
since the btf_id is unused please use
.ret_btf_id = BPF_PTR_POISON
as bpf_kptr_xchg_proto() is doing.
+
+BPF_CALL_2(bpf_rbtree_remove, struct bpf_map *, map, void *, value)
+{
+ struct bpf_rbtree *tree = container_of(map, struct bpf_rbtree, map);
+ struct rb_node *node = (struct rb_node *)value;
+
+ if (WARN_ON_ONCE(RB_EMPTY_NODE(node)))
+ return (u64)NULL;
+
+ rb_erase_cached(node, &tree->root);
+ RB_CLEAR_NODE(node);
+ return (u64)node;
+}
+
+const struct bpf_func_proto bpf_rbtree_remove_proto = {
+ .func = bpf_rbtree_remove,
+ .gpl_only = true,
+ .ret_type = RET_PTR_TO_BTF_ID_OR_NULL,
+ .ret_btf_id = &bpf_rbtree_btf_ids[0],
+ .arg1_type = ARG_CONST_MAP_PTR,
+ .arg2_type = ARG_PTR_TO_BTF_ID,
+ .arg2_btf_id = &bpf_rbtree_btf_ids[0],
same for args.
+
+BTF_ID_LIST_SINGLE(bpf_rbtree_map_btf_ids, struct, bpf_rbtree)
can be removed?
+const struct bpf_map_ops rbtree_map_ops = {
+ .map_meta_equal = bpf_map_meta_equal,
+ .map_alloc_check = rbtree_map_alloc_check,
+ .map_alloc = rbtree_map_alloc,
+ .map_free = rbtree_map_free,
+ .map_get_next_key = rbtree_map_get_next_key,
+ .map_push_elem = rbtree_map_push_elem,
+ .map_peek_elem = rbtree_map_peek_elem,
+ .map_pop_elem = rbtree_map_pop_elem,
+ .map_lookup_elem = rbtree_map_lookup_elem,
+ .map_update_elem = rbtree_map_update_elem,
+ .map_delete_elem = rbtree_map_delete_elem,
+ .map_check_btf = rbtree_map_check_btf,
+ .map_btf_id = &bpf_rbtree_map_btf_ids[0],
+};
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 1f50becce141..535f673882cd 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -481,7 +481,9 @@ static bool is_acquire_function(enum bpf_func_id func_id,
func_id == BPF_FUNC_sk_lookup_udp ||
func_id == BPF_FUNC_skc_lookup_tcp ||
func_id == BPF_FUNC_ringbuf_reserve ||
- func_id == BPF_FUNC_kptr_xchg)
+ func_id == BPF_FUNC_kptr_xchg ||
+ func_id == BPF_FUNC_rbtree_alloc_node ||
+ func_id == BPF_FUNC_rbtree_remove)
return true;
if (func_id == BPF_FUNC_map_lookup_elem &&
@@ -531,6 +533,20 @@ static bool is_cmpxchg_insn(const struct bpf_insn *insn)
insn->imm == BPF_CMPXCHG;
}
+static bool function_manipulates_rbtree_node(enum bpf_func_id func_id)
+{
+ return func_id == BPF_FUNC_rbtree_add ||
+ func_id == BPF_FUNC_rbtree_remove ||
+ func_id == BPF_FUNC_rbtree_free_node;
+}
+
+static bool function_returns_rbtree_node(enum bpf_func_id func_id)
+{
+ return func_id == BPF_FUNC_rbtree_alloc_node ||
+ func_id == BPF_FUNC_rbtree_add ||
+ func_id == BPF_FUNC_rbtree_remove;
+}
+
/* string representation of 'enum bpf_reg_type'
*
* Note that reg_type_str() can not appear more than once in a single verbose()
@@ -3784,6 +3800,13 @@ static int check_map_kptr_access(struct bpf_verifier_env *env, u32 regno,
return 0;
}
> * [ TODO: Existing logic prevents any writes to PTR_TO_BTF_ID. This
> broadly turned off in this patch and replaced with "no writes to
> struct rb_node is PTR_TO_BTF_ID struct has one". This is a hack and
> needs to be replaced. ]
..
+static bool access_may_touch_field(u32 access_off, size_t access_sz,
can_write is more accurate.
There is no ambiguity here. atype == BPF_WRITE.
+ u32 field_off, size_t field_sz)
+{
+ return access_off < field_off + field_sz &&
+ field_off < access_off + access_sz;
+}
+
/* if any part of struct field can be touched by
* load/store reject this program.
* To check that [x1, x2) overlaps with [y1, y2)
@@ -4490,7 +4513,7 @@ static int check_ptr_to_btf_access(struct bpf_verifier_env *env,
const char *tname = btf_name_by_offset(reg->btf, t->name_off);
enum bpf_type_flag flag = 0;
u32 btf_id;
- int ret;
+ int ret, rb_node_off;
if (off < 0) {
verbose(env,
@@ -4527,8 +4550,13 @@ static int check_ptr_to_btf_access(struct bpf_verifier_env *env,
off, size, atype, &btf_id, &flag);
} else {
if (atype != BPF_READ) {
- verbose(env, "only read is supported\n");
- return -EACCES;
+ rb_node_off = btf_find_rb_node(reg->btf, t);
+ if (rb_node_off < 0 ||
+ access_may_touch_field(off, size, rb_node_off,
+ sizeof(struct rb_node))) {
+ verbose(env, "only read is supported\n");
+ return -EACCES;
+ }
Allowing writes into ptr_to_btf_id probably should be a separate patch.
It's a big change.
btf_find_rb_node() alone is not enough.
Otherwise bpf progs will be able to write into any struct that has
'rb_node'.
Maybe check that reg->btf == this prog's btf ?
Also allow writes into scalars only?
All pointers in prog's struct should be __kptr anyway to be safe.
}
ret = btf_struct_access(&env->log, reg->btf, t, off, size,
@@ -5764,6 +5792,17 @@ static int check_reg_type(struct bpf_verifier_env *env, u32 regno,
if (meta->func_id == BPF_FUNC_kptr_xchg) {
if (map_kptr_match_type(env, meta->kptr_off_desc, reg, regno))
return -EACCES;
+ } else if (function_manipulates_rbtree_node(meta->func_id)) {
+ if (!btf_struct_ids_match(&env->log, reg->btf, reg->btf_id, reg->off,
+ meta->map_ptr->btf,
+ meta->map_ptr->btf_value_type_id,
+ strict_type_match)) {
+ verbose(env, "rbtree: R%d is of type %s but %s is expected\n",
+ regno, kernel_type_name(reg->btf, reg->btf_id),
+ kernel_type_name(meta->map_ptr->btf,
+ meta->map_ptr->btf_value_type_id));
+ return -EACCES;
+ }
} else if (!btf_struct_ids_match(&env->log, reg->btf, reg->btf_id, reg->off,
btf_vmlinux, *arg_btf_id,
strict_type_match)) {
@@ -6369,10 +6408,17 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env,
break;
case BPF_FUNC_map_pop_elem:
if (map->map_type != BPF_MAP_TYPE_QUEUE &&
+ map->map_type != BPF_MAP_TYPE_RBTREE &&
map->map_type != BPF_MAP_TYPE_STACK)
goto error;
break;
case BPF_FUNC_map_peek_elem:
+ if (map->map_type != BPF_MAP_TYPE_QUEUE &&
+ map->map_type != BPF_MAP_TYPE_STACK &&
+ map->map_type != BPF_MAP_TYPE_RBTREE &&
+ map->map_type != BPF_MAP_TYPE_BLOOM_FILTER)
+ goto error;
+ break;
case BPF_FUNC_map_push_elem:
if (map->map_type != BPF_MAP_TYPE_QUEUE &&
map->map_type != BPF_MAP_TYPE_STACK &&
@@ -6828,6 +6874,57 @@ static int set_loop_callback_state(struct bpf_verifier_env *env,
return 0;
}
+static int set_rbtree_add_callback_state(struct bpf_verifier_env *env,
+ struct bpf_func_state *caller,
+ struct bpf_func_state *callee,
+ int insn_idx)
+{
+ struct bpf_map *map_ptr = caller->regs[BPF_REG_1].map_ptr;
+
+ /* bpf_rbtree_add(struct bpf_map *map, void *value, void *cb)
+ * cb(struct rb_node *a, const struct rb_node *b);
+ */
+ callee->regs[BPF_REG_1].type = PTR_TO_MAP_VALUE;
+ __mark_reg_known_zero(&callee->regs[BPF_REG_1]);
+ callee->regs[BPF_REG_1].map_ptr = map_ptr;
+
+ callee->regs[BPF_REG_2].type = PTR_TO_MAP_VALUE;
+ __mark_reg_known_zero(&callee->regs[BPF_REG_2]);
+ callee->regs[BPF_REG_2].map_ptr = map_ptr;
+
+ __mark_reg_not_init(env, &callee->regs[BPF_REG_3]);
+ __mark_reg_not_init(env, &callee->regs[BPF_REG_4]);
+ __mark_reg_not_init(env, &callee->regs[BPF_REG_5]);
+ callee->in_callback_fn = true;
+ return 0;
+}
+
+static int set_rbtree_find_callback_state(struct bpf_verifier_env *env,
+ struct bpf_func_state *caller,
+ struct bpf_func_state *callee,
+ int insn_idx)
+{
+ struct bpf_map *map_ptr = caller->regs[BPF_REG_1].map_ptr;
+
+ /* bpf_rbtree_find(struct bpf_map *map, void *key, void *cb)
+ * cb(void *key, const struct rb_node *b);
+ */
+ callee->regs[BPF_REG_1].type = PTR_TO_MAP_VALUE;
+ __mark_reg_known_zero(&callee->regs[BPF_REG_1]);
+ callee->regs[BPF_REG_1].map_ptr = map_ptr;
+
+ callee->regs[BPF_REG_2].type = PTR_TO_MAP_VALUE;
+ __mark_reg_known_zero(&callee->regs[BPF_REG_2]);
+ callee->regs[BPF_REG_2].map_ptr = map_ptr;
+
+ __mark_reg_not_init(env, &callee->regs[BPF_REG_3]);
+ __mark_reg_not_init(env, &callee->regs[BPF_REG_4]);
+ __mark_reg_not_init(env, &callee->regs[BPF_REG_5]);
+ callee->in_callback_fn = true;
add and find looks the same until this point.
Reuse set_rbtree_add_callback_state here?
+ callee->callback_ret_range = tnum_range(0, U64_MAX);
that's to enforce that add's cb can only return 0 or 1 ?
But that would require bpf prog to have different cb-s for add and find.
Is this ok?
+ return 0;
+}
+
static int set_timer_callback_state(struct bpf_verifier_env *env,
struct bpf_func_state *caller,
struct bpf_func_state *callee,
@@ -7310,6 +7407,14 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
err = __check_func_call(env, insn, insn_idx_p, meta.subprogno,
set_loop_callback_state);
break;
+ case BPF_FUNC_rbtree_add:
+ err = __check_func_call(env, insn, insn_idx_p, meta.subprogno,
+ set_rbtree_add_callback_state);
+ break;
+ case BPF_FUNC_rbtree_find:
+ err = __check_func_call(env, insn, insn_idx_p, meta.subprogno,
+ set_rbtree_find_callback_state);
+ break;
case BPF_FUNC_dynptr_from_mem:
if (regs[BPF_REG_1].type != PTR_TO_MAP_VALUE) {
verbose(env, "Unsupported reg type %s for bpf_dynptr_from_mem data\n",
@@ -7424,6 +7529,9 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
if (func_id == BPF_FUNC_kptr_xchg) {
ret_btf = meta.kptr_off_desc->kptr.btf;
ret_btf_id = meta.kptr_off_desc->kptr.btf_id;
+ } else if (function_returns_rbtree_node(func_id)) {
+ ret_btf = meta.map_ptr->btf;
+ ret_btf_id = meta.map_ptr->btf_value_type_id;
} else {
ret_btf = btf_vmlinux;
ret_btf_id = *fn->ret_btf_id;
@@ -13462,8 +13570,10 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env)
BPF_SIZE((insn)->code);
env->prog->aux->num_exentries++;
} else if (resolve_prog_type(env->prog) != BPF_PROG_TYPE_STRUCT_OPS) {
+ /*TODO: Not sure what to do here
verbose(env, "Writes through BTF pointers are not allowed\n");
return -EINVAL;
+ */
Not sure whether it's worth defining PTR_TO_BTF_ID | PROGS_BTF
for writeable ptr_to_btf_id as return value from rb_alloc/find/add.
It may help here and earlier ?
All ptr_to_btf_id were kernel's or module's BTF so far.
With this change the verifier will see prog's ptr_to_btf_id that point
to prog's BTF.
PROGS_BTF might be a useful flag to have ?
Then instead of
> + } else if (function_returns_rbtree_node(func_id)) {
> + ret_btf = meta.map_ptr->btf;
> + ret_btf_id = meta.map_ptr->btf_value_type_id;
it will check PROGS_BTF flag in proto->ret_type ?
Still not fully generic, since it takes btf and btf_id from the map.
But a bit cleaner than switch() by func_id ?
