[PATCH bpf-next 7/9] bpf: Add new bpf_task_storage_delete proto with no deadlock detection

Martin KaFai Lau
2022-10-25T18:46:24Z

The bpf_lsm and bpf_iter do not recur that will cause a deadlock.
The situation is similar to the bpf_pid_task_storage_delete_elem()
which is called from the syscall map_delete_elem. It does not need
deadlock detection. Otherwise, it will cause unnecessary failure
when calling the bpf_task_storage_delete() helper.

This patch adds bpf_task_storage_delete proto that does not do deadlock
detection. It will be used by bpf_lsm and bpf_iter program.

Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
---
include/linux/bpf.h | 1 +
kernel/bpf/bpf_task_storage.c | 28 ++++++++++++++++++++++++++++
kernel/trace/bpf_trace.c | 4 +++-
3 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index ef3f98afa45d..a5dbac8f5aba 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2522,6 +2522,7 @@ extern const struct bpf_func_proto bpf_get_socket_ptr_cookie_proto;
extern const struct bpf_func_proto bpf_task_storage_get_recur_proto;
extern const struct bpf_func_proto bpf_task_storage_get_proto;
extern const struct bpf_func_proto bpf_task_storage_delete_recur_proto;
+extern const struct bpf_func_proto bpf_task_storage_delete_proto;
extern const struct bpf_func_proto bpf_for_each_map_elem_proto;
extern const struct bpf_func_proto bpf_btf_find_by_name_kind_proto;
extern const struct bpf_func_proto bpf_sk_setsockopt_proto;
diff --git a/kernel/bpf/bpf_task_storage.c b/kernel/bpf/bpf_task_storage.c
index f3f79b618a68..ba3fe72d1fa5 100644
--- a/kernel/bpf/bpf_task_storage.c
+++ b/kernel/bpf/bpf_task_storage.c
@@ -311,6 +311,25 @@ BPF_CALL_2(bpf_task_storage_delete_recur, struct bpf_map *, map, struct task_str
return ret;
}

+BPF_CALL_2(bpf_task_storage_delete, struct bpf_map *, map, struct task_struct *,
+ task)
+{
+ int ret;
+
+ WARN_ON_ONCE(!bpf_rcu_lock_held());
+ if (!task)
+ return -EINVAL;
+
+ bpf_task_storage_lock();
+ /* This helper must only be called from places where the lifetime of the task
+ * is guaranteed. Either by being refcounted or by being protected
+ * by an RCU read-side critical section.
+ */
+ ret = task_storage_delete(task, map, true);
+ bpf_task_storage_unlock();
+ return ret;
+}
+
static int notsupp_get_next_key(struct bpf_map *map, void *key, void *next_key)
{
return -ENOTSUPP;
@@ -382,3 +401,12 @@ const struct bpf_func_proto bpf_task_storage_delete_recur_proto = {
.arg2_type = ARG_PTR_TO_BTF_ID,
.arg2_btf_id = &btf_tracing_ids[BTF_TRACING_TYPE_TASK],
};
+
+const struct bpf_func_proto bpf_task_storage_delete_proto = {
+ .func = bpf_task_storage_delete,
+ .gpl_only = false,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_CONST_MAP_PTR,
+ .arg2_type = ARG_PTR_TO_BTF_ID,
+ .arg2_btf_id = &btf_tracing_ids[BTF_TRACING_TYPE_TASK],
+};
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 0986c1f0b8fc..139966c74a5a 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1493,7 +1493,9 @@ bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
return &bpf_task_storage_get_recur_proto;
return &bpf_task_storage_get_proto;
case BPF_FUNC_task_storage_delete:
- return &bpf_task_storage_delete_recur_proto;
+ if (bpf_prog_check_recur(prog))
+ return &bpf_task_storage_delete_recur_proto;
+ return &bpf_task_storage_delete_proto;
case BPF_FUNC_for_each_map_elem:
return &bpf_for_each_map_elem_proto;
case BPF_FUNC_snprintf:
--
2.30.2