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

Commit Message

Martin KaFai Lau Oct. 25, 2022, 6:45 p.m. UTC

From: Martin KaFai Lau <[e-mail]>

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 <[e-mail]>
---
 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(-)

Patch

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: