fix: additional checks for class signature

jadx-core/src/main/java/jadx/core/dex/nodes/ClassNode.java

@@ -7,6 +7,7 @@ import java.util.HashMap;
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.Set;
 
 import org.jetbrains.annotations.Nullable;
@@ -194,6 +195,10 @@ public class ClassNode extends NotificationAttrNode implements ILoadable, ICodeN
 		root().getConstValues().processConstFields(this, staticFields);
 	}
 
+	/**
+	 * Class signature format:
+	 * https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.7.9.1
+	 */
 	private void parseClassSignature() {
 		SignatureParser sp = SignatureParser.fromNode(this);
 		if (sp == null) {
@@ -203,7 +208,7 @@ public class ClassNode extends NotificationAttrNode implements ILoadable, ICodeN
 			// parse class generic map
 			generics = sp.consumeGenericTypeParameters();
 			// parse super class signature
-			superClass = sp.consumeType();
+			superClass = validateSuperCls(sp.consumeType(), superClass);
 			// parse interfaces signatures
 			for (int i = 0; i < interfaces.size(); i++) {
 				ArgType type = sp.consumeType();
@@ -218,6 +223,18 @@ public class ClassNode extends NotificationAttrNode implements ILoadable, ICodeN
 		}
 	}
 
+	private ArgType validateSuperCls(ArgType candidateType, ArgType currentType) {
+		if (!candidateType.isObject()) {
+			this.addComment("Incorrect class signature, super class is not object: " + SignatureParser.getSignature(this));
+			return currentType;
+		}
+		if (Objects.equals(candidateType.getObject(), this.getClassInfo().getType().getObject())) {
+			this.addComment("Incorrect class signature, super class is equals to this class: " + SignatureParser.getSignature(this));
+			return currentType;
+		}
+		return candidateType;
+	}
+
 	private void setFieldsTypesFromSignature() {
 		for (FieldNode field : fields) {
 			try {

jadx-core/src/main/java/jadx/core/dex/nodes/parser/SignatureParser.java

@@ -33,14 +33,23 @@ public class SignatureParser {
 		mark = 0;
 	}
 
-	@SuppressWarnings("unchecked")
+	@Nullable
 	public static SignatureParser fromNode(IAttributeNode node) {
+		String signature = getSignature(node);
+		if (signature == null) {
+			return null;
+		}
+		return new SignatureParser(signature);
+	}
+
+	@SuppressWarnings("unchecked")
+	@Nullable
+	public static String getSignature(IAttributeNode node) {
 		Annotation a = node.getAnnotation(Consts.DALVIK_SIGNATURE);
 		if (a == null) {
 			return null;
 		}
-		String signature = mergeSignature((List<String>) a.getDefaultValue());
-		return new SignatureParser(signature);
+		return mergeSignature((List<String>) a.getDefaultValue());
 	}
 
 	private char next() {

jadx-core/src/test/java/jadx/tests/integration/generics/TestClassSignature.java

@@ -0,0 +1,23 @@
+package jadx.tests.integration.generics;
+
+import org.junit.jupiter.api.Test;
+
+import jadx.tests.api.SmaliTest;
+
+import static jadx.tests.api.utils.assertj.JadxAssertions.assertThat;
+
+public class TestClassSignature extends SmaliTest {
+	// @formatter:off
+	/*
+		Incorrect class signature, super class is equals to this class: <T:Ljava/lang/Object;>Lgenerics/TestClassSignature<TT;>;
+	*/
+	// @formatter:on
+
+	@Test
+	public void test() {
+		assertThat(getClassNodeFromSmali())
+				.code()
+				.containsOne("Incorrect class signature")
+				.doesNotContain("StackOverflowError");
+	}
+}

jadx-core/src/test/smali/generics/TestClassSignature.smali

@@ -0,0 +1,115 @@
+.class public abstract Lgenerics/TestClassSignature;
+.super Ljava/lang/Object;
+.source "SourceFile"
+
+# interfaces
+.implements Ljava/util/Iterator;
+
+
+# annotations
+.annotation system Ldalvik/annotation/Signature;
+    value = {
+        "<T:",
+        "Ljava/lang/Object;",
+        ">",
+        "Lgenerics/TestClassSignature<",
+        "TT;>;"
+    }
+.end annotation
+
+
+# instance fields
+.field public f:Ljava/lang/Object;
+    .annotation system Ldalvik/annotation/Signature;
+        value = {
+            "TT;"
+        }
+    .end annotation
+.end field
+
+
+# direct methods
+.method public constructor <init>(Ljava/lang/Object;)V
+    .registers 2
+    .annotation system Ldalvik/annotation/Signature;
+        value = {
+            "(TT;)V"
+        }
+    .end annotation
+
+    invoke-direct {p0}, Ljava/lang/Object;-><init>()V
+    iput-object p1, p0, Lgenerics/TestClassSignature;->f:Ljava/lang/Object;
+    return-void
+.end method
+
+
+# virtual methods
+.method public abstract a(Ljava/lang/Object;)Ljava/lang/Object;
+    .annotation system Ldalvik/annotation/Signature;
+        value = {
+            "(TT;)TT;"
+        }
+    .end annotation
+.end method
+
+.method public final hasNext()Z
+    .registers 2
+
+    .line 1
+    iget-object v0, p0, Lgenerics/TestClassSignature;->f:Ljava/lang/Object;
+    if-eqz v0, :cond_6
+    const/4 v0, 0x1
+    goto :goto_7
+
+    :cond_6
+    const/4 v0, 0x0
+
+    :goto_7
+    return v0
+.end method
+
+.method public final next()Ljava/lang/Object;
+    .registers 3
+    .annotation system Ldalvik/annotation/Signature;
+        value = {
+            "()TT;"
+        }
+    .end annotation
+
+    invoke-virtual {p0}, Lgenerics/TestClassSignature;->hasNext()Z
+    move-result v0
+    if-eqz v0, :cond_1b
+
+    :try_start_6
+    iget-object v0, p0, Lgenerics/TestClassSignature;->f:Ljava/lang/Object;
+    :try_end_8
+    .catchall {:try_start_6 .. :try_end_8} :catchall_11
+
+    iget-object v1, p0, Lgenerics/TestClassSignature;->f:Ljava/lang/Object;
+    invoke-virtual {p0, v1}, Lgenerics/TestClassSignature;->a(Ljava/lang/Object;)Ljava/lang/Object;
+    move-result-object v1
+    iput-object v1, p0, Lgenerics/TestClassSignature;->f:Ljava/lang/Object;
+    return-object v0
+
+    :catchall_11
+    move-exception v0
+
+    iget-object v1, p0, Lgenerics/TestClassSignature;->f:Ljava/lang/Object;
+    invoke-virtual {p0, v1}, Lgenerics/TestClassSignature;->a(Ljava/lang/Object;)Ljava/lang/Object;
+    move-result-object v1
+    iput-object v1, p0, Lgenerics/TestClassSignature;->f:Ljava/lang/Object;
+    throw v0
+
+    :cond_1b
+    new-instance v0, Ljava/util/NoSuchElementException;
+    invoke-direct {v0}, Ljava/util/NoSuchElementException;-><init>()V
+    throw v0
+.end method
+
+.method public final remove()V
+    .registers 2
+
+    new-instance v0, Ljava/lang/UnsupportedOperationException;
+    invoke-direct {v0}, Ljava/lang/UnsupportedOperationException;-><init>()V
+    throw v0
+.end method