From: Kaitao Cheng Date: Sat, 14 Feb 2026 12:40:41 +0000 (+0800) Subject: bpf: allow using bpf_kptr_xchg even if the MEM_RCU flag is set X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=fb1590448ff7e79e304f9bbe662fc20334038b50;p=thirdparty%2Flinux.git bpf: allow using bpf_kptr_xchg even if the MEM_RCU flag is set For the following scenario: struct tree_node { struct bpf_refcount ref; struct bpf_rb_node node; struct node_data __kptr * node_data; u64 key; }; This means node_data would have the type PTR_TO_BTF_ID | MEM_ALLOC | NON_OWN_REF | MEM_RCU. When traversing an rbtree using bpf_rbtree_left/right, if we need to use bpf_kptr_xchg to read the __kptr pointer, we still need to follow the remove-read-add sequence. This patch allows us to use bpf_kptr_xchg to directly read the __kptr pointer without any prior operations. Signed-off-by: Kaitao Cheng Signed-off-by: Feng Yang Link: https://lore.kernel.org/r/20260214124042.62229-5-pilgrimtao@gmail.com Signed-off-by: Alexei Starovoitov --- diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 7426dba5e5d1c..1153a828ce8df 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -9311,6 +9311,7 @@ static const struct bpf_reg_types kptr_xchg_dest_types = { PTR_TO_MAP_VALUE, PTR_TO_BTF_ID | MEM_ALLOC, PTR_TO_BTF_ID | MEM_ALLOC | NON_OWN_REF, + PTR_TO_BTF_ID | MEM_ALLOC | NON_OWN_REF | MEM_RCU, } }; static const struct bpf_reg_types dynptr_types = { @@ -9475,6 +9476,7 @@ found: 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: + case PTR_TO_BTF_ID | MEM_ALLOC | NON_OWN_REF | MEM_RCU: 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");