[PATCH RESEND v3 2/3] bpf/verifier: allow using bpf_kptr_xchg even if the NON_OWN_REF flag is set

[Chengkaitao <pilgrimtao@gmail.com>]

From: Chengkaitao <chengkaitao@kylinos.cn>

When traversing an rbtree using bpf_rbtree_left/right, if bpf_kptr_xchg
is used to access the __kptr pointer contained in a node, it currently
requires first removing the node with bpf_rbtree_remove and clearing the
NON_OWN_REF flag, then re-adding the node to the original rbtree with
bpf_rbtree_add after usage. This process significantly degrades rbtree
traversal performance. The patch enables accessing __kptr pointers with
the NON_OWN_REF flag set while holding the lock, eliminating the need
for this remove-read-readd sequence.

Signed-off-by: Chengkaitao <chengkaitao@kylinos.cn>
Signed-off-by: Feng Yang <yangfeng@kylinos.cn>
---
 kernel/bpf/verifier.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 05a6a6606b6c..bb3ff4bbb3a2 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -9260,7 +9260,8 @@ static const struct bpf_reg_types timer_types = { .types = { PTR_TO_MAP_VALUE }
 static const struct bpf_reg_types kptr_xchg_dest_types = {
 	.types = {
 		PTR_TO_MAP_VALUE,
-		PTR_TO_BTF_ID | MEM_ALLOC
+		PTR_TO_BTF_ID | MEM_ALLOC,
+		PTR_TO_BTF_ID | MEM_ALLOC | NON_OWN_REF
 	}
 };
 static const struct bpf_reg_types dynptr_types = {
@@ -9420,6 +9421,7 @@ static int check_reg_type(struct bpf_verifier_env *env, u32 regno,
 	}
 	case PTR_TO_BTF_ID | MEM_ALLOC:
 	case PTR_TO_BTF_ID | MEM_PERCPU | MEM_ALLOC:
+	case PTR_TO_BTF_ID | MEM_ALLOC | NON_OWN_REF:
 		if (meta->func_id != BPF_FUNC_spin_lock && meta->func_id != BPF_FUNC_spin_unlock &&
 		    meta->func_id != BPF_FUNC_kptr_xchg) {
 			verifier_bug(env, "unimplemented handling of MEM_ALLOC");
-- 
2.50.1 (Apple Git-155)