[PATCH bpf-next 5/9] bpf: Add new bpf_task_storage_get proto with no deadlock detection

Martin KaFai Lau
2022-10-25T18:46:21Z

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

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

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 | 5 ++++-
3 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index b04fe3f4342e..ef3f98afa45d 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2520,6 +2520,7 @@ extern const struct bpf_func_proto bpf_ktime_get_coarse_ns_proto;
extern const struct bpf_func_proto bpf_sock_from_file_proto;
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_for_each_map_elem_proto;
extern const struct bpf_func_proto bpf_btf_find_by_name_kind_proto;
diff --git a/kernel/bpf/bpf_task_storage.c b/kernel/bpf/bpf_task_storage.c
index bc52bc8b59f7..c3a841be438f 100644
--- a/kernel/bpf/bpf_task_storage.c
+++ b/kernel/bpf/bpf_task_storage.c
@@ -269,6 +269,23 @@ BPF_CALL_5(bpf_task_storage_get_recur, struct bpf_map *, map, struct task_struct
return (unsigned long)data;
}

+/* *gfp_flags* is a hidden argument provided by the verifier */
+BPF_CALL_5(bpf_task_storage_get, struct bpf_map *, map, struct task_struct *,
+ task, void *, value, u64, flags, gfp_t, gfp_flags)
+{
+ void *data;
+
+ WARN_ON_ONCE(!bpf_rcu_lock_held());
+ if (flags & ~BPF_LOCAL_STORAGE_GET_F_CREATE || !task)
+ return (unsigned long)NULL;
+
+ bpf_task_storage_lock();
+ data = __bpf_task_storage_get(map, task, value, flags,
+ gfp_flags, true);
+ bpf_task_storage_unlock();
+ return (unsigned long)data;
+}
+
BPF_CALL_2(bpf_task_storage_delete_recur, struct bpf_map *, map, struct task_struct *,
task)
{
@@ -342,6 +359,17 @@ const struct bpf_func_proto bpf_task_storage_get_recur_proto = {
.arg4_type = ARG_ANYTHING,
};

+const struct bpf_func_proto bpf_task_storage_get_proto = {
+ .func = bpf_task_storage_get,
+ .gpl_only = false,
+ .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL,
+ .arg1_type = ARG_CONST_MAP_PTR,
+ .arg2_type = ARG_PTR_TO_BTF_ID,
+ .arg2_btf_id = &btf_tracing_ids[BTF_TRACING_TYPE_TASK],
+ .arg3_type = ARG_PTR_TO_MAP_VALUE_OR_NULL,
+ .arg4_type = ARG_ANYTHING,
+};
+
const struct bpf_func_proto bpf_task_storage_delete_recur_proto = {
.func = bpf_task_storage_delete_recur,
.gpl_only = false,
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 591caf0eb973..0986c1f0b8fc 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -6,6 +6,7 @@
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/bpf.h>
+#include <linux/bpf_verifier.h>
#include <linux/bpf_perf_event.h>
#include <linux/btf.h>
#include <linux/filter.h>
@@ -1488,7 +1489,9 @@ bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
case BPF_FUNC_this_cpu_ptr:
return &bpf_this_cpu_ptr_proto;
case BPF_FUNC_task_storage_get:
- return &bpf_task_storage_get_recur_proto;
+ if (bpf_prog_check_recur(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;
case BPF_FUNC_for_each_map_elem:
--
2.30.2