Fix infinite loop with bad section ends in TastyHeaderUnpickler

compiler/src/dotty/tools/dotc/core/tasty/PositionPickler.scala

@@ -3,15 +3,15 @@ package dotc
 package core
 package tasty
 
-import dotty.tools.tasty.TastyFormat.{SOURCE, PositionsSection}
-import dotty.tools.tasty.TastyBuffer
+import dotty.tools.tasty.TastyFormat.{PositionsSection, SOURCE}
+import dotty.tools.tasty.{PickleException, TastyBuffer}
 import TastyBuffer.*
-
 import ast.*
 import Trees.WithLazyFields
-import util.{SourceFile, NoSource}
+import util.{NoSource, SourceFile}
 import core.*
-import Annotations.*, Decorators.*
+import Annotations.*
+import Decorators.*
 import collection.mutable
 import util.Spans.*
 import reporting.Message
@@ -48,6 +48,9 @@ object PositionPickler:
       val content = source.content()
       buf.writeNat(content.count(_ == '\n') + 1) // number of lines
       var lastIndex = content.indexOf('\n', 0)
+      if (lastIndex == -1) {
+        lastIndex = 0
+      }
       buf.writeNat(lastIndex) // size of first line
       while lastIndex != -1 do
         val nextIndex = content.indexOf('\n', lastIndex + 1)

compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala

@@ -188,7 +188,7 @@ class TreeUnpickler(reader: TastyReader,
       if (tag >= firstLengthTreeTag) goto(readEnd())
       else if (tag >= firstNatASTTreeTag) { readNat(); skipTree() }
       else if (tag >= firstASTTreeTag) skipTree()
-      else if (tag >= firstNatTreeTag) readNat()
+      else if (tag >= firstNatTreeTag) readLongInt()
     }
     def skipTree(): Unit = skipTree(readByte())
 
@@ -225,7 +225,7 @@ class TreeUnpickler(reader: TastyReader,
           if (mode == MemberDefsOnly) skipTree(tag)
           else if (tag >= firstLengthTreeTag) {
             val end = readEnd()
-            var nrefs = numRefs(tag)
+            val nrefs = numRefs(tag)
             if (nrefs < 0) {
               for (i <- nrefs until 0) scanTree(buf)
               goto(end)
@@ -241,7 +241,7 @@ class TreeUnpickler(reader: TastyReader,
           }
           else if (tag >= firstNatASTTreeTag) { readNat(); scanTree(buf) }
           else if (tag >= firstASTTreeTag) scanTree(buf)
-          else if (tag >= firstNatTreeTag) readNat()
+          else if (tag >= firstNatTreeTag) readLongInt()
       }
     }
 

compiler/test/dotty/tools/dotc/core/tasty/TastyUnpickerTest.scala

@@ -0,0 +1,59 @@
+package dotty.tools.dotc.core.tasty
+
+import dotty.tools.io.VirtualFile
+import dotty.tools.dotc.core.Contexts.*
+import dotty.tools.dotc.ast.*
+import dotty.tools.dotc.ast.tpd.*
+import dotty.tools.tasty.UnpickleException
+import org.junit.Test
+import org.junit.Assert.*
+
+class TastyUnpickerTest {
+  private def test(bytes: Int*): Unit =
+    val base = new ContextBase
+    given Context = base.initialCtx.fresh
+    val bytesArray = bytes.map(_.toByte).toArray
+    val dotty = new DottyUnpickler(
+      tastyFile = new VirtualFile("bytes.tasty", bytesArray),
+      bytes = bytesArray,
+      isBestEffortTasty = false
+    )
+    dotty.enter(roots = Set.empty)
+    dotty.rootTrees.foreach(t => t.foreachSubTree(identity))
+
+  // this used to go into an infinite loop as we could 'goto' a negative number when looking for a section end
+  @Test def regressionInfiniteLoop(): Unit =
+    assertThrows(classOf[UnpickleException], () => test(
+      0x5c, 0xa1, 0xab, 0x1f, 0x9c, 0x88, 0x80, 0xb8, 0x53, 0x63, 0x61, 0x6c, 0x61, 0x20, 0x33, 0x2e, 0x38, 0x2e, 0x32, 0x2d,
+      0x52, 0x43, 0x31, 0x2d, 0x62, 0x69, 0x6e, 0x2d, 0x53, 0x4e, 0x41, 0xb0, 0xac, 0xb7, 0xa9, 0x54, 0x2d, 0x6e, 0x6f, 0x6e,
+      0x62, 0x9a, 0x90, 0x8b, 0x8c, 0x74, 0x72, 0x0a, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x6f, 0x6f, 0x6c, 0x77, 0x2e,
+      0x64, 0x6f, 0x74, 0x3c, 0x00, 0xd5, 0x86, 0x0a, 0xd0, 0x5b, 0x65, 0xe8, 0x00, 0xd4, 0x9d, 0xda, 0xab, 0x1f, 0x3b, 0x18,
+      0x02, 0xb6, 0x01, 0x84, 0x41, 0x53, 0x54, 0x73, 0x01, 0x85, 0x7a, 0x63, 0x61, 0x6c, 0x61, 0x01, 0x8a, 0x61, 0x6e, 0x6e,
+      0x6f, 0x74, 0x61, 0x74, 0x69, 0x6f, 0x6e, 0x02, 0x82, 0x81, 0x82, 0x01, 0x8c, 0x65, 0x78, 0x70, 0x65, 0x72, 0x69, 0x93,
+      0x9a, 0x91, 0x8b, 0x61, 0x6c, 0x01, 0x88, 0x6c, 0x5d, 0x6e, 0x67, 0x75, 0x61, 0x67, 0x65, 0x01, 0x8f, 0x63, 0x61, 0x70,
+      0x74, 0x75, 0x72, 0x65, 0x43, 0x68, 0x65, 0x63, 0x6b, 0x69, 0x6e, 0x67, 0x01, 0x86, 0x75, 0x6e, 0x72, 0x6f, 0x6c, 0x6c,
+      0x01, 0x86, 0x3c, 0x69, 0x6e, 0x69, 0x74, 0x3e, 0x01, 0x8a, 0x41, 0x6e, 0x6e, 0x6f, 0x69, 0x61, 0x74, 0x74, 0x6f, 0x6e,
+      0x02, 0x82, 0x83, 0x89, 0x3f, 0x82, 0x88, 0x8a, 0x01, 0x90, 0x53, 0x74, 0x61, 0x74, 0x69, 0x63, 0x41, 0x6e, 0x6e, 0x6e,
+      0x69, 0x0b, 0x00, 0x6f, 0x6f, 0x61, 0x01, 0x84, 0x55, 0x6e, 0x69, 0x74, 0x01, 0x8a, 0x53, 0x6f, 0x75, 0x72, 0x63, 0x65,
+      0x46, 0x69, 0x6c, 0x65, 0x01, 0x88, 0x69, 0x6e, 0x74, 0x65, 0x72, 0x6e, 0x61, 0x6c, 0x02, 0x82, 0x83, 0x8f, 0x02, 0x82,
+      0x90, 0x8e, 0x01, 0x84, 0x6a, 0x61, 0x76, 0x61, 0x01, 0x84, 0x6c, 0x61, 0x6e, 0x67, 0x02, 0x82, 0x92, 0x93, 0x01, 0x86,
+      0x53, 0x5d, 0x72, 0x69, 0x6c, 0x67, 0x02, 0x82, 0x94, 0x95, 0x3f, 0x83, 0x88, 0x91, 0x96, 0x01, 0xa9, 0x6c, 0x69, 0x62,
+      0x72, 0x61, 0x72, 0x79, 0x2f, 0x73, 0x72, 0x63, 0x2f, 0x73, 0x63, 0x61, 0x6c, 0x61, 0x2f, 0x61, 0x6e, 0x6e, 0x6f, 0x74,
+      0x61, 0x74, 0x69, 0x6f, 0x6e, 0x2f, 0x75, 0x6e, 0x72, 0x6f, 0x6c, 0x6c, 0x2e, 0x73, 0x63, 0x61, 0x6c, 0x61, 0x02, 0x82,
+      0x83, 0x84, 0x3f, 0x83, 0x88, 0x99, 0x96, 0x01, 0x9e, 0x75, 0x6e, 0x64, 0xa3, 0x8d, 0xdf, 0x8d, 0x9a, 0x89, 0x96, 0x9a,
+      0x77, 0x20, 0x61, 0x73, 0x20, 0x70, 0x61, 0x72, 0x74, 0x20, 0x6f, 0x66, 0x20, 0x53, 0x49, 0x50, 0x2d, 0x34, 0x36, 0x01,
+      0x89, 0x50, 0x6f, 0xd7, 0x69, 0x74, 0x69, 0x6f, 0x6e, 0x73, 0x01, 0x88, 0x41, 0x6f, 0x6d, 0x6d, 0x65, 0x6e, 0x74, 0x73,
+      0x01, 0x8a, 0x41, 0x74, 0x74, 0x72, 0x69, 0x62, 0x81, 0x74, 0x6d, 0x72, 0x80, 0xd5, 0x84, 0x83, 0x72, 0xdd, 0x2e, 0x47,
+      0xe1, 0x13, 0x24, 0x38, 0x40, 0x40, 0x81, 0x4b, 0x86, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x86, 0x86,
+      0x86, 0x86, 0x86, 0x86, 0x86, 0x86, 0x86, 0x12, 0x12, 0x12, 0x12, 0x12, 0x12, 0x12, 0x0f, 0x0f, 0x09, 0x09, 0x09, 0x09,
+      0x09, 0x09, 0x09, 0x09, 0x09, 0x09, 0x09, 0x26, 0x26, 0x26, 0x26, 0x26, 0x26, 0x26, 0x26, 0x26, 0x26, 0x26, 0x26, 0x26,
+      0x26, 0x26, 0x26, 0x26, 0x26, 0x26, 0x26, 0x26, 0x26, 0x26, 0x26, 0x26, 0x26, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x9e, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f,
+      0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f,
+      0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f,
+      0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f,
+      0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f,
+      0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f, 0x7f,
+      0x7f, 0x85, 0x02, 0x03, 0x04, 0x81, 0x98,
+    ) )
+}

tasty/src/dotty/tools/tasty/PickleException.scala

@@ -0,0 +1,3 @@
+package dotty.tools.tasty
+
+class PickleException(msg: String) extends RuntimeException(msg)

tasty/src/dotty/tools/tasty/TastyBuffer.scala

@@ -64,14 +64,18 @@ class TastyBuffer(initialSize: Int) {
     length += n
   }
 
-  /** Write a natural number in big endian format, base 128.
-   *  All but the last digits have bit 0x80 set.
+  /** Write a natural number in big endian format, base 128, as octets.
+   *  All octets but the last have bit 0x80 unset.
    */
-  def writeNat(x: Int): Unit =
+  def writeNat(x: Int): Unit = {
+    if (x < 0) {
+      throw new PickleException(s"Expected a natural (nonnegative) number to write, but got: $x")
+    }
     writeLongNat(x.toLong & 0x00000000FFFFFFFFL)
+  }
 
-  /** Write a natural number in 2's complement big endian format, base 128.
-   *  All but the last digits have bit 0x80 set.
+  /** Write a natural number in 2's complement big endian format, base 128, as octets.
+   *  All octets but the last have bit 0x80 unset.
    */
   def writeInt(x: Int): Unit =
     writeLongInt(x)
@@ -83,6 +87,9 @@ class TastyBuffer(initialSize: Int) {
    * Int.MAX_VALUE.
    */
   def writeLongNat(x: Long): Unit = {
+    if (x < 0) {
+      throw new PickleException(s"Expected a natural (nonnegative) number to write, but got: $x")
+    }
     def writePrefix(x: Long): Unit = {
       val y = x >>> 7
       if (y != 0L) writePrefix(y)

tasty/src/dotty/tools/tasty/TastyReader.scala

@@ -28,7 +28,7 @@ class TastyReader(val bytes: Array[Byte], start: Int, end: Int, val base: Int =
   /** The address of the next byte to read */
   def currentAddr: Addr = addr(bp)
 
-  /** the address one greater than the last brte to read */
+  /** the address one greater than the last byte to read */
   def endAddr: Addr = addr(end)
 
   /** Have all bytes been read? */
@@ -58,34 +58,55 @@ class TastyReader(val bytes: Array[Byte], start: Int, end: Int, val base: Int =
     result
   }
 
-  /** Read a natural number fitting in an Int in big endian format, base 128.
-   *  All but the last digits have bit 0x80 set.
+  /** Read a 31-bit natural (nonnegative) integer number in 2's complement big endian format, base 128, stored as octets.
+   *  All octets but the last have bit 0x80 unset.
    */
-  def readNat(): Int = readLongNat().toInt
+  def readNat(): Int = {
+    val l = readLongNat()
+    if (l > Int.MaxValue) {
+      throw new UnpickleException(s"Expected a 31-bit nat, got: $l")
+    }
+    l.toInt
+  }
 
-  /** Read an integer number in 2's complement big endian format, base 128.
-   *  All but the last digits have bit 0x80 set.
+  /** Read a 32-bit integer number in 2's complement big endian format, base 128, stored as octets.
+   *  All octets but the last have bit 0x80 unset.
    */
-  def readInt(): Int = readLongInt().toInt
+  def readInt(): Int = {
+    val l = readLongInt()
+    if (l < Int.MinValue || l > Int.MaxValue) {
+      throw new UnpickleException(s"Expected a 32-bit int, got: $l")
+    }
+    l.toInt
+  }
 
-  /** Read a natural number fitting in a Long in big endian format, base 128.
-   *  All but the last digits have bit 0x80 set.
+  /** Read a 63-bit natural (nonnegative) number in 2's complement big endian format, base 128, stored as octets.
+   *  All octets but the last have bit 0x80 unset.
    */
   def readLongNat(): Long = {
+    val ogBp = bp
     var b = 0L
     var x = 0L
     while ({
       b = bytes(bp)
       x = (x << 7) | (b & 0x7f)
       bp += 1
       (b & 0x80) == 0
-    })
-    ()
+    }) ()
+    if (bp - ogBp > 9) {
+      throw new UnpickleException(s"Expected a long nat, but read too many bytes (${bp - ogBp})")
+    }
+    if (x < 0) {
+      throw new UnpickleException(s"Expected a nat, got: $x")
+    }
     x
   }
 
-  /** Read a long integer number in 2's complement big endian format, base 128. */
+  /** Read a 64-bit long integer number in 2's complement big endian format, base 128, stored as octets.
+   *  All octets but the last have bit 0x80 unset.
+   */
   def readLongInt(): Long = {
+    val ogBp = bp
     var b = bytes(bp)
     var x: Long = (b << 1).toByte >> 1 // sign extend with bit 6.
     bp += 1
@@ -94,6 +115,9 @@ class TastyReader(val bytes: Array[Byte], start: Int, end: Int, val base: Int =
       x = (x << 7) | (b & 0x7f)
       bp += 1
     }
+    if (bp - ogBp > 10) {
+      throw new UnpickleException(s"Expected a long int, but read too many bytes (${bp - ogBp})")
+    }
     x
   }