From: Kaitao Cheng <[email protected]> If a user holds ownership of a node in the middle of a list, they can directly remove it from the list without strictly adhering to deletion rules from the head or tail.
We have added an additional parameter bpf_list_head *head to bpf_list_del, as the verifier requires the head parameter to check whether the lock is being held. This is typically paired with bpf_refcount. After calling bpf_list_del, it is generally necessary to drop the reference to the list node twice to prevent reference count leaks. Signed-off-by: Kaitao Cheng <[email protected]> --- kernel/bpf/helpers.c | 11 +++++++++++ kernel/bpf/verifier.c | 4 ++++ 2 files changed, 15 insertions(+) diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index e87b263c5fe6..dac346eb1e2f 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -2437,6 +2437,8 @@ static struct bpf_list_node *__bpf_list_del(struct bpf_list_head *head, */ if (unlikely(!h->next)) INIT_LIST_HEAD(h); + + /* verifier to guarantee n is a list node rather than the head */ if (list_empty(h)) return NULL; @@ -2463,6 +2465,14 @@ __bpf_kfunc struct bpf_list_node *bpf_list_pop_back(struct bpf_list_head *head) return __bpf_list_del(head, h->prev); } +__bpf_kfunc struct bpf_list_node *bpf_list_del(struct bpf_list_head *head, + struct bpf_list_node *node) +{ + struct bpf_list_node_kern *kn = (void *)node; + + return __bpf_list_del(head, &kn->list_head); +} + __bpf_kfunc struct bpf_list_node *bpf_list_front(struct bpf_list_head *head) { struct list_head *h = (struct list_head *)head; @@ -4549,6 +4559,7 @@ BTF_ID_FLAGS(func, bpf_list_push_front_impl) BTF_ID_FLAGS(func, bpf_list_push_back_impl) BTF_ID_FLAGS(func, bpf_list_pop_front, KF_ACQUIRE | KF_RET_NULL) BTF_ID_FLAGS(func, bpf_list_pop_back, KF_ACQUIRE | KF_RET_NULL) +BTF_ID_FLAGS(func, bpf_list_del, KF_ACQUIRE | KF_RET_NULL) BTF_ID_FLAGS(func, bpf_list_front, KF_RET_NULL) BTF_ID_FLAGS(func, bpf_list_back, KF_RET_NULL) BTF_ID_FLAGS(func, bpf_task_acquire, KF_ACQUIRE | KF_RCU | KF_RET_NULL) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 64c1f8343dfa..e928ad4290c7 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -12508,6 +12508,7 @@ enum special_kfunc_type { KF_bpf_list_push_back_impl, KF_bpf_list_pop_front, KF_bpf_list_pop_back, + KF_bpf_list_del, KF_bpf_list_front, KF_bpf_list_back, KF_bpf_cast_to_kern_ctx, @@ -12568,6 +12569,7 @@ BTF_ID(func, bpf_list_push_front_impl) BTF_ID(func, bpf_list_push_back_impl) BTF_ID(func, bpf_list_pop_front) BTF_ID(func, bpf_list_pop_back) +BTF_ID(func, bpf_list_del) BTF_ID(func, bpf_list_front) BTF_ID(func, bpf_list_back) BTF_ID(func, bpf_cast_to_kern_ctx) @@ -12644,6 +12646,7 @@ static const enum special_kfunc_type bpf_list_api_kfuncs[] = { KF_bpf_list_push_back_impl, KF_bpf_list_pop_front, KF_bpf_list_pop_back, + KF_bpf_list_del, KF_bpf_list_front, KF_bpf_list_back, }; @@ -12652,6 +12655,7 @@ static const enum special_kfunc_type bpf_list_api_kfuncs[] = { static const enum special_kfunc_type bpf_list_node_api_kfuncs[] = { KF_bpf_list_push_front_impl, KF_bpf_list_push_back_impl, + KF_bpf_list_del, }; /* Kfuncs that take an rbtree node argument (bpf_rb_node *). */ -- 2.50.1 (Apple Git-155)
