On 11/28/22 6:37 PM, Yonghong Song wrote:
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index c05aa6e1f6f5..6f192dd9025e 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -683,7 +683,7 @@ static inline bool bpf_prog_check_recur(const struct bpf_prog *prog)
}
}
-#define BPF_REG_TRUSTED_MODIFIERS (MEM_ALLOC | MEM_RCU | PTR_TRUSTED)
+#define BPF_REG_TRUSTED_MODIFIERS (MEM_ALLOC | PTR_TRUSTED)
[ ... ]
+static bool is_rcu_reg(const struct bpf_reg_state *reg)
+{
+ return reg->type & MEM_RCU;
+}
+
static int check_pkt_ptr_alignment(struct bpf_verifier_env *env,
const struct bpf_reg_state *reg,
int off, int size, bool strict)
@@ -4775,12 +4780,10 @@ static int check_ptr_to_btf_access(struct bpf_verifier_env *env,
/* Mark value register as MEM_RCU only if it is protected by
* bpf_rcu_read_lock() and the ptr reg is trusted. MEM_RCU
* itself can already indicate trustedness inside the rcu
- * read lock region. Also mark it as PTR_TRUSTED.
+ * read lock region.
*/
if (!env->cur_state->active_rcu_lock || !is_trusted_reg(reg))
flag &= ~MEM_RCU;
How about dereferencing a PTR_TO_BTF_ID | MEM_RCU, like:
/* parent: PTR_TO_BTF_ID | MEM_RCU */
parent = current->real_parent;
/* gparent: PTR_TO_BTF_ID */
gparent = parent->real_parent;
Should "gparent" have MEM_RCU also?
Also, should PTR_MAYBE_NULL be added to "parent"?
- else
- flag |= PTR_TRUSTED;
} else if (reg->type & MEM_RCU) {
/* ptr (reg) is marked as MEM_RCU, but the struct field is not tagged
* with __rcu. Mark the flag as PTR_UNTRUSTED conservatively.
@@ -5945,7 +5948,7 @@ static const struct bpf_reg_types btf_ptr_types = {
.types = {
PTR_TO_BTF_ID,
PTR_TO_BTF_ID | PTR_TRUSTED,
- PTR_TO_BTF_ID | MEM_RCU | PTR_TRUSTED,
+ PTR_TO_BTF_ID | MEM_RCU,
},
};
static const struct bpf_reg_types percpu_btf_ptr_types = {
@@ -6124,7 +6127,7 @@ int check_func_arg_reg_off(struct bpf_verifier_env *env,
case PTR_TO_BTF_ID:
case PTR_TO_BTF_ID | MEM_ALLOC:
case PTR_TO_BTF_ID | PTR_TRUSTED:
- case PTR_TO_BTF_ID | MEM_RCU | PTR_TRUSTED:
+ case PTR_TO_BTF_ID | MEM_RCU:
case PTR_TO_BTF_ID | MEM_ALLOC | PTR_TRUSTED:
/* When referenced PTR_TO_BTF_ID is passed to release function,
* it's fixed offset must be 0. In the other cases, fixed offset
@@ -8022,6 +8025,11 @@ static bool is_kfunc_destructive(struct bpf_kfunc_call_arg_meta *meta)
return meta->kfunc_flags & KF_DESTRUCTIVE;
}
+static bool is_kfunc_rcu(struct bpf_kfunc_call_arg_meta *meta)
+{
+ return meta->kfunc_flags & KF_RCU;
+}
+
static bool is_kfunc_arg_kptr_get(struct bpf_kfunc_call_arg_meta *meta, int arg)
{
return arg == 0 && (meta->kfunc_flags & KF_KPTR_GET);
@@ -8706,13 +8714,19 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
switch (kf_arg_type) {
case KF_ARG_PTR_TO_ALLOC_BTF_ID:
case KF_ARG_PTR_TO_BTF_ID:
- if (!is_kfunc_trusted_args(meta))
+ if (!is_kfunc_trusted_args(meta) && !is_kfunc_rcu(meta))
break;
- if (!is_trusted_reg(reg)) {
- verbose(env, "R%d must be referenced or trusted\n", regno);
+ if (!is_trusted_reg(reg) && !is_rcu_reg(reg)) {
+ verbose(env, "R%d must be referenced, trusted or rcu\n", regno);
return -EINVAL;
}
+
+ if (is_kfunc_rcu(meta) != is_rcu_reg(reg)) {
I think is_trusted_reg(reg) should also be acceptable to bpf_task_acquire_rcu().
nit. bpf_task_acquire_not_zero() may be a better kfunc name.
+ verbose(env, "R%d does not match kf arg rcu tagging\n", regno);
+ return -EINVAL;
+ }
+
fallthrough;
case KF_ARG_PTR_TO_CTX:
/* Trusted arguments have the same offset checks as release arguments */
@@ -8823,7 +8837,7 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
case KF_ARG_PTR_TO_BTF_ID:
/* Only base_type is checked, further checks are done here */
if ((base_type(reg->type) != PTR_TO_BTF_ID ||
- bpf_type_has_unsafe_modifiers(reg->type)) &&
+ (bpf_type_has_unsafe_modifiers(reg->type) && !is_rcu_reg(reg))) &&
!reg2btf_ids[base_type(reg->type)]) {
verbose(env, "arg#%d is %s ", i, reg_type_str(env, reg->type));
verbose(env, "expected %s or socket\n",
@@ -8938,7 +8952,7 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
} else if (rcu_unlock) {
bpf_for_each_reg_in_vstate(env->cur_state, state, reg, ({
if (reg->type & MEM_RCU) {
- reg->type &= ~(MEM_RCU | PTR_TRUSTED);
+ reg->type &= ~MEM_RCU;
reg->type |= PTR_UNTRUSTED;
}
}));
diff --git a/tools/testing/selftests/bpf/prog_tests/cgrp_kfunc.c b/tools/testing/selftests/bpf/prog_tests/cgrp_kfunc.c
index 973f0c5af965..5fbd9edd2c4c 100644
--- a/tools/testing/selftests/bpf/prog_tests/cgrp_kfunc.c
+++ b/tools/testing/selftests/bpf/prog_tests/cgrp_kfunc.c
@@ -93,10 +93,10 @@ static struct {
const char *prog_name;
const char *expected_err_msg;
} failure_tests[] = {
- {"cgrp_kfunc_acquire_untrusted", "R1 must be referenced or trusted"},
+ {"cgrp_kfunc_acquire_untrusted", "R1 must be referenced, trusted or rcu"},
{"cgrp_kfunc_acquire_fp", "arg#0 pointer type STRUCT cgroup must point"},
{"cgrp_kfunc_acquire_unsafe_kretprobe", "reg type unsupported for arg#0 function"},
- {"cgrp_kfunc_acquire_trusted_walked", "R1 must be referenced or trusted"},
+ {"cgrp_kfunc_acquire_trusted_walked", "R1 must be referenced, trusted or rcu"},
{"cgrp_kfunc_acquire_null", "arg#0 pointer type STRUCT cgroup must point"},
{"cgrp_kfunc_acquire_unreleased", "Unreleased reference"},
{"cgrp_kfunc_get_non_kptr_param", "arg#0 expected pointer to map value"},
diff --git a/tools/testing/selftests/bpf/prog_tests/task_kfunc.c b/tools/testing/selftests/bpf/prog_tests/task_kfunc.c
index ffd8ef4303c8..80708c073de6 100644
--- a/tools/testing/selftests/bpf/prog_tests/task_kfunc.c
+++ b/tools/testing/selftests/bpf/prog_tests/task_kfunc.c
@@ -87,10 +87,10 @@ static struct {
const char *prog_name;
const char *expected_err_msg;
} failure_tests[] = {
- {"task_kfunc_acquire_untrusted", "R1 must be referenced or trusted"},
+ {"task_kfunc_acquire_untrusted", "R1 must be referenced, trusted or rcu"},
{"task_kfunc_acquire_fp", "arg#0 pointer type STRUCT task_struct must point"},
{"task_kfunc_acquire_unsafe_kretprobe", "reg type unsupported for arg#0 function"},
- {"task_kfunc_acquire_trusted_walked", "R1 must be referenced or trusted"},
+ {"task_kfunc_acquire_trusted_walked", "R1 must be referenced, trusted or rcu"},
hmm... why this description is changed here? The bpf_task_acquire kfunc-flags
has not changed.
