| Message ID | 20230403200027.2271029-1-davemarchevsky@fb.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | f6a6a5a976288e4d0d94eb1c6c9e983e8e5cdb31 |
| Delegated to: | BPF |
| Headers | show |
| Series | [bpf-next] bpf: Fix struct_meta lookup for bpf_obj_free_fields kfunc call | expand |
Hello: This patch was applied to bpf/bpf-next.git (master) by Alexei Starovoitov <ast@kernel.org>: On Mon, 3 Apr 2023 13:00:27 -0700 you wrote: > bpf_obj_drop_impl has a void return type. In check_kfunc_call, the "else > if" which sets insn_aux->kptr_struct_meta for bpf_obj_drop_impl is > surrounded by a larger if statement which checks btf_type_is_ptr. As a > result: > > * The bpf_obj_drop_impl-specific code will never execute > * The btf_struct_meta input to bpf_obj_drop is always NULL > * __bpf_obj_drop_impl will always see a NULL btf_record when called > from BPF program, and won't call bpf_obj_free_fields > * program-allocated kptrs which have fields that should be cleaned up > by bpf_obj_free_fields may instead leak resources > > [...] Here is the summary with links: - [bpf-next] bpf: Fix struct_meta lookup for bpf_obj_free_fields kfunc call https://git.kernel.org/bpf/bpf-next/c/f6a6a5a97628 You are awesome, thank you!
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 92ae4e8ab87b..eaf9c5291cf0 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -10743,10 +10743,6 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, insn_aux->obj_new_size = ret_t->size; insn_aux->kptr_struct_meta = btf_find_struct_meta(ret_btf, ret_btf_id); - } else if (meta.func_id == special_kfunc_list[KF_bpf_obj_drop_impl]) { - insn_aux->kptr_struct_meta = - btf_find_struct_meta(meta.arg_obj_drop.btf, - meta.arg_obj_drop.btf_id); } else if (meta.func_id == special_kfunc_list[KF_bpf_list_pop_front] || meta.func_id == special_kfunc_list[KF_bpf_list_pop_back]) { struct btf_field *field = meta.arg_list_head.field; @@ -10875,7 +10871,15 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, if (reg_may_point_to_spin_lock(®s[BPF_REG_0]) && !regs[BPF_REG_0].id) regs[BPF_REG_0].id = ++env->id_gen; - } /* else { add_kfunc_call() ensures it is btf_type_is_void(t) } */ + } else if (btf_type_is_void(t)) { + if (meta.btf == btf_vmlinux && btf_id_set_contains(&special_kfunc_set, meta.func_id)) { + if (meta.func_id == special_kfunc_list[KF_bpf_obj_drop_impl]) { + insn_aux->kptr_struct_meta = + btf_find_struct_meta(meta.arg_obj_drop.btf, + meta.arg_obj_drop.btf_id); + } + } + } nargs = btf_type_vlen(meta.func_proto); args = (const struct btf_param *)(meta.func_proto + 1);
bpf_obj_drop_impl has a void return type. In check_kfunc_call, the "else if" which sets insn_aux->kptr_struct_meta for bpf_obj_drop_impl is surrounded by a larger if statement which checks btf_type_is_ptr. As a result: * The bpf_obj_drop_impl-specific code will never execute * The btf_struct_meta input to bpf_obj_drop is always NULL * __bpf_obj_drop_impl will always see a NULL btf_record when called from BPF program, and won't call bpf_obj_free_fields * program-allocated kptrs which have fields that should be cleaned up by bpf_obj_free_fields may instead leak resources This patch adds a btf_type_is_void branch to the larger if and moves special handling for bpf_obj_drop_impl there, fixing the issue. Fixes: ac9f06050a35 ("bpf: Introduce bpf_obj_drop") Cc: Kumar Kartikeya Dwivedi <memxor@gmail.com> Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com> --- This was previously sent to apply against bpf tree (https://lore.kernel.org/bpf/20230403173125.1056883-1-davemarchevsky@fb.com/), but we decided to go through bpf-next instead. kernel/bpf/verifier.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-)