Introduce support for KF_ARG_PTR_TO_WORKQUEUE. The kfuncs will use bpf_wq as argument and that will be recognized as workqueue argument by verifier. bpf_wq_kern casting can happen inside kfunc, but using bpf_wq in argument makes life easier for users who work with non-kern type in BPF progs.
Duplicate process_timer_func into process_wq_func. meta argument is only needed to ensure bpf_wq_init's workqueue and map arguments are coming from the same map (map_uid logic is necessary for correct inner-map handling), so also amend check_kfunc_args() to match what helpers functions check is doing.
Signed-off-by: Benjamin Tissoires bentiss@kernel.org
---
changes in v2: - clean up already done checks in process_wq_func() - adjust comment - gate check_kfunc_args check with map->record->wq_off. --- kernel/bpf/verifier.c | 65 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 65 insertions(+)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index b95fd63864f1..5ff7b52d9032 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -332,6 +332,10 @@ struct bpf_kfunc_call_arg_meta { u8 spi; u8 frameno; } iter; + struct { + struct bpf_map *ptr; + int uid; + } map; u64 mem_size; };
@@ -7598,6 +7602,23 @@ static int process_timer_func(struct bpf_verifier_env *env, int regno, return 0; }
+static int process_wq_func(struct bpf_verifier_env *env, int regno, + struct bpf_kfunc_call_arg_meta *meta) +{ + struct bpf_reg_state *regs = cur_regs(env), *reg = ®s[regno]; + struct bpf_map *map = reg->map_ptr; + u64 val = reg->var_off.value; + + if (map->record->wq_off != val + reg->off) { + verbose(env, "off %lld doesn't point to 'struct bpf_wq' that is at %d\n", + val + reg->off, map->record->wq_off); + return -EINVAL; + } + meta->map.uid = reg->map_uid; + meta->map.ptr = map; + return 0; +} + static int process_kptr_func(struct bpf_verifier_env *env, int regno, struct bpf_call_arg_meta *meta) { @@ -10843,6 +10864,7 @@ enum { KF_ARG_LIST_NODE_ID, KF_ARG_RB_ROOT_ID, KF_ARG_RB_NODE_ID, + KF_ARG_WORKQUEUE_ID, };
BTF_ID_LIST(kf_arg_btf_ids) @@ -10851,6 +10873,7 @@ BTF_ID(struct, bpf_list_head) BTF_ID(struct, bpf_list_node) BTF_ID(struct, bpf_rb_root) BTF_ID(struct, bpf_rb_node) +BTF_ID(struct, bpf_wq)
static bool __is_kfunc_ptr_arg_type(const struct btf *btf, const struct btf_param *arg, int type) @@ -10894,6 +10917,11 @@ static bool is_kfunc_arg_rbtree_node(const struct btf *btf, const struct btf_par return __is_kfunc_ptr_arg_type(btf, arg, KF_ARG_RB_NODE_ID); }
+static bool is_kfunc_arg_wq(const struct btf *btf, const struct btf_param *arg) +{ + return __is_kfunc_ptr_arg_type(btf, arg, KF_ARG_WORKQUEUE_ID); +} + static bool is_kfunc_arg_callback(struct bpf_verifier_env *env, const struct btf *btf, const struct btf_param *arg) { @@ -10963,6 +10991,7 @@ enum kfunc_ptr_arg_type { KF_ARG_PTR_TO_NULL, KF_ARG_PTR_TO_CONST_STR, KF_ARG_PTR_TO_MAP, + KF_ARG_PTR_TO_WORKQUEUE, };
enum special_kfunc_type { @@ -11119,6 +11148,9 @@ get_kfunc_ptr_arg_type(struct bpf_verifier_env *env, if (is_kfunc_arg_map(meta->btf, &args[argno])) return KF_ARG_PTR_TO_MAP;
+ if (is_kfunc_arg_wq(meta->btf, &args[argno])) + return KF_ARG_PTR_TO_WORKQUEUE; + if ((base_type(reg->type) == PTR_TO_BTF_ID || reg2btf_ids[base_type(reg->type)])) { if (!btf_type_is_struct(ref_t)) { verbose(env, "kernel function %s args#%d pointer type %s %s is not supported\n", @@ -11724,6 +11756,29 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_ verbose(env, "pointer in R%d isn't map pointer\n", regno); return -EINVAL; } + if (meta->map.ptr && reg->map_ptr->record->wq_off >= 0) { + /* Use map_uid (which is unique id of inner map) to reject: + * inner_map1 = bpf_map_lookup_elem(outer_map, key1) + * inner_map2 = bpf_map_lookup_elem(outer_map, key2) + * if (inner_map1 && inner_map2) { + * wq = bpf_map_lookup_elem(inner_map1); + * if (wq) + * // mismatch would have been allowed + * bpf_wq_init(wq, inner_map2); + * } + * + * Comparing map_ptr is enough to distinguish normal and outer maps. + */ + if (meta->map.ptr != reg->map_ptr || + meta->map.uid != reg->map_uid) { + verbose(env, + "workqueue pointer in R1 map_uid=%d doesn't match map pointer in R2 map_uid=%d\n", + meta->map.uid, reg->map_uid); + return -EINVAL; + } + } + meta->map.ptr = reg->map_ptr; + meta->map.uid = reg->map_uid; fallthrough; case KF_ARG_PTR_TO_ALLOC_BTF_ID: case KF_ARG_PTR_TO_BTF_ID: @@ -11757,6 +11812,7 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_ case KF_ARG_PTR_TO_CALLBACK: case KF_ARG_PTR_TO_REFCOUNTED_KPTR: case KF_ARG_PTR_TO_CONST_STR: + case KF_ARG_PTR_TO_WORKQUEUE: /* Trusted by default */ break; default: @@ -12043,6 +12099,15 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_ if (ret) return ret; break; + case KF_ARG_PTR_TO_WORKQUEUE: + if (reg->type != PTR_TO_MAP_VALUE) { + verbose(env, "arg#%d doesn't point to a map value\n", i); + return -EINVAL; + } + ret = process_wq_func(env, regno, meta); + if (ret < 0) + return ret; + break; } }