bpf: Factor out atomic_ptr_type_ok()

JIRA: https://issues.redhat.com/browse/RHEL-78202

commit 66faaea
Author: Peilin Ye <yepeilin@google.com>
Date:   Mon Mar 3 05:37:07 2025 +0000

    bpf: Factor out atomic_ptr_type_ok()
    
    Factor out atomic_ptr_type_ok() as a helper function to be used later.
    
    Signed-off-by: Peilin Ye <yepeilin@google.com>
    Link: https://lore.kernel.org/r/e5ef8b3116f3fffce78117a14060ddce05eba52a.1740978603.git.yepeilin@google.com
    Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Signed-off-by: Gregory Bell <grbell@redhat.com>

Author: Gbell26

kernel/bpf/verifier.c

@@ -6195,6 +6195,26 @@ static bool is_arena_reg(struct bpf_verifier_env *env, int regno)
 	return reg->type == PTR_TO_ARENA;
 }
 
+/* Return false if @regno contains a pointer whose type isn't supported for
+ * atomic instruction @insn.
+ */
+static bool atomic_ptr_type_ok(struct bpf_verifier_env *env, int regno,
+			       struct bpf_insn *insn)
+{
+	if (is_ctx_reg(env, regno))
+		return false;
+	if (is_pkt_reg(env, regno))
+		return false;
+	if (is_flow_key_reg(env, regno))
+		return false;
+	if (is_sk_reg(env, regno))
+		return false;
+	if (is_arena_reg(env, regno))
+		return bpf_jit_supports_insn(insn, true);
+
+	return true;
+}
+
 static u32 *reg2btf_ids[__BPF_REG_TYPE_MAX] = {
 #ifdef CONFIG_NET
 	[PTR_TO_SOCKET] = &btf_sock_ids[BTF_SOCK_TYPE_SOCK],
@@ -7652,11 +7672,7 @@ static int check_atomic(struct bpf_verifier_env *env, int insn_idx, struct bpf_i
 		return -EACCES;
 	}
 
-	if (is_ctx_reg(env, insn->dst_reg) ||
-	    is_pkt_reg(env, insn->dst_reg) ||
-	    is_flow_key_reg(env, insn->dst_reg) ||
-	    is_sk_reg(env, insn->dst_reg) ||
-	    (is_arena_reg(env, insn->dst_reg) && !bpf_jit_supports_insn(insn, true))) {
+	if (!atomic_ptr_type_ok(env, insn->dst_reg, insn)) {
 		verbose(env, "BPF_ATOMIC stores into R%d %s is not allowed\n",
 			insn->dst_reg,
 			reg_type_str(env, reg_state(env, insn->dst_reg)->type));