bpf: Move off_reg into sanitize_ptr_alu

mainline inclusion
from mainline-v5.12-rc8
commit 6f55b2f2
category: bugfix
bugzilla: NA
CVE: CVE-2021-29155

--------------------------------

Small refactor to drag off_reg into sanitize_ptr_alu(), so we later on can
use off_reg for generalizing some of the checks for all pointer types.
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>
Reviewed-by: NJohn Fastabend <john.fastabend@gmail.com>
Acked-by: NAlexei Starovoitov <ast@kernel.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
Reviewed-by: NKuohai Xu <xukuohai@huawei.com>
Reviewed-by: NXiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

kernel/bpf/verifier.c

@@ -2799,11 +2799,12 @@ static int sanitize_val_alu(struct bpf_verifier_env *env,
 static int sanitize_ptr_alu(struct bpf_verifier_env *env,
 			    struct bpf_insn *insn,
 			    const struct bpf_reg_state *ptr_reg,
-			    struct bpf_reg_state *dst_reg,
-			    bool off_is_neg)
+			    const struct bpf_reg_state *off_reg,
+			    struct bpf_reg_state *dst_reg)
 {
 	struct bpf_verifier_state *vstate = env->cur_state;
 	struct bpf_insn_aux_data *aux = cur_aux(env);
+	bool off_is_neg = off_reg->smin_value < 0;
 	bool ptr_is_dst_reg = ptr_reg == dst_reg;
 	u8 opcode = BPF_OP(insn->code);
 	u32 alu_state, alu_limit;
@@ -2927,7 +2928,7 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
 
 	switch (opcode) {
 	case BPF_ADD:
-		ret = sanitize_ptr_alu(env, insn, ptr_reg, dst_reg, smin_val < 0);
+		ret = sanitize_ptr_alu(env, insn, ptr_reg, off_reg, dst_reg);
 		if (ret < 0) {
 			verbose(env, "R%d tried to add from different maps, paths, or prohibited types\n", dst);
 			return ret;
@@ -2982,7 +2983,7 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
 		}
 		break;
 	case BPF_SUB:
-		ret = sanitize_ptr_alu(env, insn, ptr_reg, dst_reg, smin_val < 0);
+		ret = sanitize_ptr_alu(env, insn, ptr_reg, off_reg, dst_reg);
 		if (ret < 0) {
 			verbose(env, "R%d tried to sub from different maps, paths, or prohibited types\n", dst);
 			return ret;