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Message-Id: <20240416-bpf_wq-v1-8-c9e66092f842@kernel.org>
Date: Tue, 16 Apr 2024 16:08:21 +0200
From: Benjamin Tissoires <bentiss@...nel.org>
To: Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>,
Martin KaFai Lau <martin.lau@...ux.dev>,
Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>,
Yonghong Song <yonghong.song@...ux.dev>,
John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>,
Stanislav Fomichev <sdf@...gle.com>, Hao Luo <haoluo@...gle.com>,
Jiri Olsa <jolsa@...nel.org>, Mykola Lysenko <mykolal@...com>,
Shuah Khan <shuah@...nel.org>
Cc: bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-kselftest@...r.kernel.org, Benjamin Tissoires <bentiss@...nel.org>
Subject: [PATCH bpf-next 08/18] bpf: add support for
KF_ARG_PTR_TO_WORKQUEUE
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@...nel.org>
---
kernel/bpf/verifier.c | 86 +++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 86 insertions(+)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index deaf2e1ab690..112faf2cd7e9 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 +7602,43 @@ 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];
+ bool is_const = tnum_is_const(reg->var_off);
+ struct bpf_map *map = reg->map_ptr;
+ u64 val = reg->var_off.value;
+
+ if (!is_const) {
+ verbose(env,
+ "R%d doesn't have constant offset. bpf_wq has to be at the constant offset\n",
+ regno);
+ return -EINVAL;
+ }
+ if (!map->btf) {
+ verbose(env, "map '%s' has to have BTF in order to use bpf_wq\n",
+ map->name);
+ return -EINVAL;
+ }
+ if (!btf_record_has_field(map->record, BPF_WORKQUEUE)) {
+ verbose(env, "map '%s' has no valid bpf_wq\n", map->name);
+ return -EINVAL;
+ }
+ 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;
+ }
+ if (meta->map.ptr) {
+ verbose(env, "verifier bug. Two map pointers in a workqueue helper\n");
+ return -EFAULT;
+ }
+ 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 +10884,7 @@ 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 +10893,7 @@ 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 +10937,11 @@ 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 +11011,7 @@ 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 +11168,9 @@ 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",
@@ -11720,6 +11772,30 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
case KF_ARG_PTR_TO_NULL:
continue;
case KF_ARG_PTR_TO_MAP:
+ if (meta->map.ptr) {
+ /* 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) {
+ * timer = bpf_map_lookup_elem(inner_map1);
+ * if (timer)
+ * // mismatch would have been allowed
+ * bpf_timer_init(timer, 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:
if (!is_kfunc_trusted_args(meta) && !is_kfunc_rcu(meta))
@@ -11752,6 +11828,7 @@ 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:
@@ -12038,6 +12115,15 @@ 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;
}
}
--
2.44.0
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