1 files changed, 66 insertions, 28 deletions

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index a57db4b2803c..fe9a513e2314 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3990,6 +3990,12 @@ static int __check_ptr_off_reg(struct bpf_verifier_env *env,
 	 * is only allowed in its original, unmodified form.
 	 */
 
+	if (reg->off < 0) {
+		verbose(env, "negative offset %s ptr R%d off=%d disallowed\n",
+			reg_type_str(env, reg->type), regno, reg->off);
+		return -EACCES;
+	}
+
 	if (!fixed_off_ok && reg->off) {
 		verbose(env, "dereference of modified %s ptr R%d off=%d disallowed\n",
 			reg_type_str(env, reg->type), regno, reg->off);
@@ -5359,6 +5365,60 @@ found:
 	return 0;
 }
 
+int check_func_arg_reg_off(struct bpf_verifier_env *env,
+			   const struct bpf_reg_state *reg, int regno,
+			   enum bpf_arg_type arg_type,
+			   bool is_release_func)
+{
+	bool fixed_off_ok = false, release_reg;
+	enum bpf_reg_type type = reg->type;
+
+	switch ((u32)type) {
+	case SCALAR_VALUE:
+	/* Pointer types where reg offset is explicitly allowed: */
+	case PTR_TO_PACKET:
+	case PTR_TO_PACKET_META:
+	case PTR_TO_MAP_KEY:
+	case PTR_TO_MAP_VALUE:
+	case PTR_TO_MEM:
+	case PTR_TO_MEM | MEM_RDONLY:
+	case PTR_TO_MEM | MEM_ALLOC:
+	case PTR_TO_BUF:
+	case PTR_TO_BUF | MEM_RDONLY:
+	case PTR_TO_STACK:
+		/* Some of the argument types nevertheless require a
+		 * zero register offset.
+		 */
+		if (arg_type != ARG_PTR_TO_ALLOC_MEM)
+			return 0;
+		break;
+	/* All the rest must be rejected, except PTR_TO_BTF_ID which allows
+	 * fixed offset.
+	 */
+	case PTR_TO_BTF_ID:
+		/* When referenced PTR_TO_BTF_ID is passed to release function,
+		 * it's fixed offset must be 0. We rely on the property that
+		 * only one referenced register can be passed to BPF helpers and
+		 * kfuncs. In the other cases, fixed offset can be non-zero.
+		 */
+		release_reg = is_release_func && reg->ref_obj_id;
+		if (release_reg && reg->off) {
+			verbose(env, "R%d must have zero offset when passed to release func\n",
+				regno);
+			return -EINVAL;
+		}
+		/* For release_reg == true, fixed_off_ok must be false, but we
+		 * already checked and rejected reg->off != 0 above, so set to
+		 * true to allow fixed offset for all other cases.
+		 */
+		fixed_off_ok = true;
+		break;
+	default:
+		break;
+	}
+	return __check_ptr_off_reg(env, reg, regno, fixed_off_ok);
+}
+
 static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 			  struct bpf_call_arg_meta *meta,
 			  const struct bpf_func_proto *fn)
@@ -5408,36 +5468,14 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 	if (err)
 		return err;
 
-	switch ((u32)type) {
-	case SCALAR_VALUE:
-	/* Pointer types where reg offset is explicitly allowed: */
-	case PTR_TO_PACKET:
-	case PTR_TO_PACKET_META:
-	case PTR_TO_MAP_KEY:
-	case PTR_TO_MAP_VALUE:
-	case PTR_TO_MEM:
-	case PTR_TO_MEM | MEM_RDONLY:
-	case PTR_TO_MEM | MEM_ALLOC:
-	case PTR_TO_BUF:
-	case PTR_TO_BUF | MEM_RDONLY:
-	case PTR_TO_STACK:
-		/* Some of the argument types nevertheless require a
-		 * zero register offset.
-		 */
-		if (arg_type == ARG_PTR_TO_ALLOC_MEM)
-			goto force_off_check;
-		break;
-	/* All the rest must be rejected: */
-	default:
-force_off_check:
-		err = __check_ptr_off_reg(env, reg, regno,
-					  type == PTR_TO_BTF_ID);
-		if (err < 0)
-			return err;
-		break;
-	}
+	err = check_func_arg_reg_off(env, reg, regno, arg_type, is_release_function(meta->func_id));
+	if (err)
+		return err;
 
 skip_type_check:
+	/* check_func_arg_reg_off relies on only one referenced register being
+	 * allowed for BPF helpers.
+	 */
 	if (reg->ref_obj_id) {
 		if (meta->ref_obj_id) {
 			verbose(env, "verifier internal error: more than one arg with ref_obj_id R%d %u %u\n",