diff --git a/core/src/main/scala/org/apache/spark/scheduler/dynalloc/ExecutorMonitor.scala b/core/src/main/scala/org/apache/spark/scheduler/dynalloc/ExecutorMonitor.scala
index f5beb403555e9..d0337b6e34962 100644
--- a/core/src/main/scala/org/apache/spark/scheduler/dynalloc/ExecutorMonitor.scala
+++ b/core/src/main/scala/org/apache/spark/scheduler/dynalloc/ExecutorMonitor.scala
@@ -182,19 +182,19 @@ private[spark] class ExecutorMonitor(
     if (updateExecutors) {
       val activeShuffleIds = shuffleStages.map(_._2).toSeq
       var needTimeoutUpdate = false
-      val activatedExecs = new mutable.ArrayBuffer[String]()
+      val activatedExecs = new ExecutorIdCollector()
       executors.asScala.foreach { case (id, exec) =>
         if (!exec.hasActiveShuffle) {
           exec.updateActiveShuffles(activeShuffleIds)
           if (exec.hasActiveShuffle) {
             needTimeoutUpdate = true
-            activatedExecs += id
+            activatedExecs.add(id)
           }
         }
       }
 
-      logDebug(s"Activated executors ${activatedExecs.mkString(",")} due to shuffle data " +
-        s"needed by new job ${event.jobId}.")
+      logDebug(s"Activated executors $activatedExecs due to shuffle data needed by new job" +
+        s"${event.jobId}.")
 
       if (needTimeoutUpdate) {
         nextTimeout.set(Long.MinValue)
@@ -233,18 +233,18 @@ private[spark] class ExecutorMonitor(
         }
       }
 
-      val deactivatedExecs = new mutable.ArrayBuffer[String]()
+      val deactivatedExecs = new ExecutorIdCollector()
       executors.asScala.foreach { case (id, exec) =>
         if (exec.hasActiveShuffle) {
           exec.updateActiveShuffles(activeShuffles)
           if (!exec.hasActiveShuffle) {
-            deactivatedExecs += id
+            deactivatedExecs.add(id)
           }
         }
       }
 
-      logDebug(s"Executors ${deactivatedExecs.mkString(",")} do not have active shuffle data " +
-        s"after job ${event.jobId} finished.")
+      logDebug(s"Executors $deactivatedExecs do not have active shuffle data after job " +
+        s"${event.jobId} finished.")
     }
 
     jobToStageIDs.remove(event.jobId).foreach { stages =>
@@ -448,7 +448,8 @@ private[spark] class ExecutorMonitor(
         } else {
           idleTimeoutMs
         }
-        idleStart + timeout
+        val deadline = idleStart + timeout
+        if (deadline >= 0) deadline else Long.MaxValue
       } else {
         Long.MaxValue
       }
@@ -491,4 +492,22 @@ private[spark] class ExecutorMonitor(
   private case class ShuffleCleanedEvent(id: Int) extends SparkListenerEvent {
     override protected[spark] def logEvent: Boolean = false
   }
+
+  /** Used to collect executor IDs for debug messages (and avoid too long messages). */
+  private class ExecutorIdCollector {
+    private val ids = if (log.isDebugEnabled) new mutable.ArrayBuffer[String]() else null
+    private var excess = 0
+
+    def add(id: String): Unit = if (log.isDebugEnabled) {
+      if (ids.size < 10) {
+        ids += id
+      } else {
+        excess += 1
+      }
+    }
+
+    override def toString(): String = {
+      ids.mkString(",") + (if (excess > 0) s" (and $excess more)" else "")
+    }
+  }
 }
diff --git a/core/src/test/scala/org/apache/spark/scheduler/dynalloc/ExecutorMonitorSuite.scala b/core/src/test/scala/org/apache/spark/scheduler/dynalloc/ExecutorMonitorSuite.scala
index e11ee97469b00..6a25754fcbe5a 100644
--- a/core/src/test/scala/org/apache/spark/scheduler/dynalloc/ExecutorMonitorSuite.scala
+++ b/core/src/test/scala/org/apache/spark/scheduler/dynalloc/ExecutorMonitorSuite.scala
@@ -367,6 +367,26 @@ class ExecutorMonitorSuite extends SparkFunSuite {
     assert(monitor.timedOutExecutors(idleDeadline).toSet === Set("1", "2"))
   }
 
+  test("SPARK-28455: avoid overflow in timeout calculation") {
+    conf
+      .set(DYN_ALLOCATION_SHUFFLE_TIMEOUT, Long.MaxValue)
+      .set(DYN_ALLOCATION_SHUFFLE_TRACKING, true)
+      .set(SHUFFLE_SERVICE_ENABLED, false)
+    monitor = new ExecutorMonitor(conf, client, null, clock)
+
+    // Generate events that will make executor 1 be idle, while still holding shuffle data.
+    // The executor should not be eligible for removal since the timeout is basically "infinite".
+    val stage = stageInfo(1, shuffleId = 0)
+    monitor.onJobStart(SparkListenerJobStart(1, clock.getTimeMillis(), Seq(stage)))
+    clock.advance(1000L)
+    monitor.onExecutorAdded(SparkListenerExecutorAdded(clock.getTimeMillis(), "1", null))
+    monitor.onTaskStart(SparkListenerTaskStart(1, 0, taskInfo("1", 1)))
+    monitor.onTaskEnd(SparkListenerTaskEnd(1, 0, "foo", Success, taskInfo("1", 1), null))
+    monitor.onJobEnd(SparkListenerJobEnd(1, clock.getTimeMillis(), JobSucceeded))
+
+    assert(monitor.timedOutExecutors(idleDeadline).isEmpty)
+  }
+
   private def idleDeadline: Long = clock.getTimeMillis() + idleTimeoutMs + 1
   private def storageDeadline: Long = clock.getTimeMillis() + storageTimeoutMs + 1
   private def shuffleDeadline: Long = clock.getTimeMillis() + shuffleTimeoutMs + 1