[PATCH v3 6/7] bpf: Fix dtor CFI

[Peter Zijlstra <peterz@xxxxxxxxxxxxx>]

Ensure the various dtor functions match their prototype and retain
their CFI signatures, since they don't have their address taken, they
are prone to not getting CFI, making them impossible to call
indirectly.

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
 kernel/bpf/cpumask.c |    8 +++++++-
 kernel/bpf/helpers.c |   16 ++++++++++++++--
 net/bpf/test_run.c   |   15 +++++++++++++--
 3 files changed, 34 insertions(+), 5 deletions(-)

--- a/kernel/bpf/cpumask.c
+++ b/kernel/bpf/cpumask.c
@@ -96,6 +96,12 @@ __bpf_kfunc void bpf_cpumask_release(str
 	migrate_enable();
 }
 
+__bpf_kfunc void bpf_cpumask_release_dtor(void *cpumask)
+{
+	bpf_cpumask_release(cpumask);
+}
+CFI_NOSEAL(bpf_cpumask_release_dtor);
+
 /**
  * bpf_cpumask_first() - Get the index of the first nonzero bit in the cpumask.
  * @cpumask: The cpumask being queried.
@@ -441,7 +447,7 @@ static const struct btf_kfunc_id_set cpu
 
 BTF_ID_LIST(cpumask_dtor_ids)
 BTF_ID(struct, bpf_cpumask)
-BTF_ID(func, bpf_cpumask_release)
+BTF_ID(func, bpf_cpumask_release_dtor)
 
 static int __init cpumask_kfunc_init(void)
 {
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2150,6 +2150,12 @@ __bpf_kfunc void bpf_task_release(struct
 	put_task_struct_rcu_user(p);
 }
 
+__bpf_kfunc void bpf_task_release_dtor(void *p)
+{
+	put_task_struct_rcu_user(p);
+}
+CFI_NOSEAL(bpf_task_release_dtor);
+
 #ifdef CONFIG_CGROUPS
 /**
  * bpf_cgroup_acquire - Acquire a reference to a cgroup. A cgroup acquired by
@@ -2174,6 +2180,12 @@ __bpf_kfunc void bpf_cgroup_release(stru
 	cgroup_put(cgrp);
 }
 
+__bpf_kfunc void bpf_cgroup_release_dtor(void *cgrp)
+{
+	cgroup_put(cgrp);
+}
+CFI_NOSEAL(bpf_cgroup_release_dtor);
+
 /**
  * bpf_cgroup_ancestor - Perform a lookup on an entry in a cgroup's ancestor
  * array. A cgroup returned by this kfunc which is not subsequently stored in a
@@ -2570,10 +2582,10 @@ static const struct btf_kfunc_id_set gen
 
 BTF_ID_LIST(generic_dtor_ids)
 BTF_ID(struct, task_struct)
-BTF_ID(func, bpf_task_release)
+BTF_ID(func, bpf_task_release_dtor)
 #ifdef CONFIG_CGROUPS
 BTF_ID(struct, cgroup)
-BTF_ID(func, bpf_cgroup_release)
+BTF_ID(func, bpf_cgroup_release_dtor)
 #endif
 
 BTF_SET8_START(common_btf_ids)
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -600,10 +600,21 @@ __bpf_kfunc void bpf_kfunc_call_test_rel
 	refcount_dec(&p->cnt);
 }
 
+__bpf_kfunc void bpf_kfunc_call_test_release_dtor(void *p)
+{
+	bpf_kfunc_call_test_release(p);
+}
+CFI_NOSEAL(bpf_kfunc_call_test_release_dtor);
+
 __bpf_kfunc void bpf_kfunc_call_memb_release(struct prog_test_member *p)
 {
 }
 
+__bpf_kfunc void bpf_kfunc_call_memb_release_dtor(void *p)
+{
+}
+CFI_NOSEAL(bpf_kfunc_call_memb_release_dtor);
+
 __bpf_kfunc_end_defs();
 
 BTF_SET8_START(bpf_test_modify_return_ids)
@@ -1671,9 +1682,9 @@ static const struct btf_kfunc_id_set bpf
 
 BTF_ID_LIST(bpf_prog_test_dtor_kfunc_ids)
 BTF_ID(struct, prog_test_ref_kfunc)
-BTF_ID(func, bpf_kfunc_call_test_release)
+BTF_ID(func, bpf_kfunc_call_test_release_dtor)
 BTF_ID(struct, prog_test_member)
-BTF_ID(func, bpf_kfunc_call_memb_release)
+BTF_ID(func, bpf_kfunc_call_memb_release_dtor)
 
 static int __init bpf_prog_test_run_init(void)
 {