In verifier.c, fixup_kfunc_call uses struct bpf_insn_aux_data's
kptr_struct_meta field to pass information about local kptr types to
various helpers and kfuncs at runtime. The recent bpf_refcount series
added a few functions to the set that need this information:
* bpf_refcount_acquire
* Needs to know where the refcount field is in order to increment
* Graph collection insert kfuncs: bpf_rbtree_add, bpf_list_push_{front,back}
* Were migrated to possibly fail by the bpf_refcount series. If
insert fails, the input node is bpf_obj_drop'd. bpf_obj_drop needs
the kptr_struct_meta in order to decr refcount and properly free
special fields.
Unfortunately the verifier handling of collection insert kfuncs was not
modified to actually populate kptr_struct_meta. Accordingly, when the
node input to those kfuncs is passed to bpf_obj_drop, it is done so
without the information necessary to decr refcount.
This patch fixes the issue by populating kptr_struct_meta for those
kfuncs.
Fixes: d2dcc67df910 ("bpf: Migrate bpf_rbtree_add and bpf_list_push_{front,back} to possibly fail")
Signed-off-by: Dave Marchevsky <davemarchevsky@xxxxxx>
---
kernel/bpf/verifier.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 6f39534ded2e..26c072e34834 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -299,6 +299,7 @@ struct bpf_kfunc_call_arg_meta {
union {
struct btf_and_id arg_obj_drop;
struct btf_and_id arg_refcount_acquire;
+ struct btf_and_id arg_graph_node;
};
struct {
struct btf_field *field;
@@ -10158,6 +10159,8 @@ __process_kf_arg_ptr_to_graph_node(struct bpf_verifier_env *env,
node_off, btf_name_by_offset(reg->btf, t->name_off));
return -EINVAL;
}
+ meta->arg_graph_node.btf = reg->btf;
+ meta->arg_graph_node.btf_id = reg->btf_id;
if (node_off != field->graph_root.node_offset) {
verbose(env, "arg#1 offset=%d, but expected %s at offset=%d in struct %s\n",
@@ -10720,6 +10723,8 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
meta.func_id == special_kfunc_list[KF_bpf_rbtree_add_impl]) {
release_ref_obj_id = regs[BPF_REG_2].ref_obj_id;
insn_aux->insert_off = regs[BPF_REG_2].off;
+ insn_aux->kptr_struct_meta = btf_find_struct_meta(meta.arg_graph_node.btf,
+ meta.arg_graph_node.btf_id);
err = ref_convert_owning_non_owning(env, release_ref_obj_id);
if (err) {
verbose(env, "kfunc %s#%d conversion of owning ref to non-owning failed\n",
--
2.34.1
