bpf: Do register range validation early

Instead of checking src/dst range multiple times during
the main verifier pass do them once.

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260403024422.87231-2-alexei.starovoitov@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

2 files changed, 10 insertions, 28 deletions

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 5434b162c930..9de49d43c21d 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2256,13 +2256,6 @@ static void __mark_reg_const_zero(const struct bpf_verifier_env *env, struct bpf
 static void mark_reg_known_zero(struct bpf_verifier_env *env,
 				struct bpf_reg_state *regs, u32 regno)
 {
-	if (WARN_ON(regno >= MAX_BPF_REG)) {
-		verbose(env, "mark_reg_known_zero(regs, %u)\n", regno);
-		/* Something bad happened, let's kill all regs */
-		for (regno = 0; regno < MAX_BPF_REG; regno++)
-			__mark_reg_not_init(env, regs + regno);
-		return;
-	}
 	__mark_reg_known_zero(regs + regno);
 }
 
@@ -2936,13 +2929,6 @@ static void __mark_reg_unknown(const struct bpf_verifier_env *env,
 static void mark_reg_unknown(struct bpf_verifier_env *env,
 			     struct bpf_reg_state *regs, u32 regno)
 {
-	if (WARN_ON(regno >= MAX_BPF_REG)) {
-		verbose(env, "mark_reg_unknown(regs, %u)\n", regno);
-		/* Something bad happened, let's kill all regs except FP */
-		for (regno = 0; regno < BPF_REG_FP; regno++)
-			__mark_reg_not_init(env, regs + regno);
-		return;
-	}
 	__mark_reg_unknown(env, regs + regno);
 }
 
@@ -2975,13 +2961,6 @@ static void __mark_reg_not_init(const struct bpf_verifier_env *env,
 static void mark_reg_not_init(struct bpf_verifier_env *env,
 			      struct bpf_reg_state *regs, u32 regno)
 {
-	if (WARN_ON(regno >= MAX_BPF_REG)) {
-		verbose(env, "mark_reg_not_init(regs, %u)\n", regno);
-		/* Something bad happened, let's kill all regs except FP */
-		for (regno = 0; regno < BPF_REG_FP; regno++)
-			__mark_reg_not_init(env, regs + regno);
-		return;
-	}
 	__mark_reg_not_init(env, regs + regno);
 }
 
@@ -3986,11 +3965,6 @@ static int __check_reg_arg(struct bpf_verifier_env *env, struct bpf_reg_state *r
 	struct bpf_reg_state *reg;
 	bool rw64;
 
-	if (regno >= MAX_BPF_REG) {
-		verbose(env, "R%d is invalid\n", regno);
-		return -EINVAL;
-	}
-
 	mark_reg_scratched(env, regno);
 
 	reg = &regs[regno];
@@ -21999,6 +21973,14 @@ static int resolve_pseudo_ldimm64(struct bpf_verifier_env *env)
 		return err;
 
 	for (i = 0; i < insn_cnt; i++, insn++) {
+		if (insn->dst_reg >= MAX_BPF_REG) {
+			verbose(env, "R%d is invalid\n", insn->dst_reg);
+			return -EINVAL;
+		}
+		if (insn->src_reg >= MAX_BPF_REG) {
+			verbose(env, "R%d is invalid\n", insn->src_reg);
+			return -EINVAL;
+		}
 		if (BPF_CLASS(insn->code) == BPF_LDX &&
 		    ((BPF_MODE(insn->code) != BPF_MEM && BPF_MODE(insn->code) != BPF_MEMSX) ||
 		    insn->imm != 0)) {
diff --git a/tools/testing/selftests/bpf/verifier/junk_insn.c b/tools/testing/selftests/bpf/verifier/junk_insn.c
index 89d690f1992a..7d10b0a48f51 100644
--- a/tools/testing/selftests/bpf/verifier/junk_insn.c
+++ b/tools/testing/selftests/bpf/verifier/junk_insn.c
@@ -28,7 +28,7 @@
 {
 	"junk insn4",
 	.insns = {
-	BPF_RAW_INSN(-1, -1, -1, -1, -1),
+	BPF_RAW_INSN(-1, 0, 0, -1, -1),
 	BPF_EXIT_INSN(),
 	},
 	.errstr = "unknown opcode ff",
@@ -37,7 +37,7 @@
 {
 	"junk insn5",
 	.insns = {
-	BPF_RAW_INSN(0x7f, -1, -1, -1, -1),
+	BPF_RAW_INSN(0x7f, 0, 0, -1, -1),
 	BPF_EXIT_INSN(),
 	},
 	.errstr = "BPF_ALU uses reserved fields",