(tomcat) 03/03: Fix regression

This is an automated email from the ASF dual-hosted git repository.

markt-asf pushed a commit to branch 9.0.x
in repository https://gitbox.apache.org/repos/asf/tomcat.git

commit b86cd17d51a3b0805043e7438efcb23f8a5fdb3d
Author: Mark Thomas <[email protected]>
AuthorDate: Wed Jul 1 11:52:35 2026 +0100

    Fix regression
    
    Co-written with GPT-5.5
---
 java/org/apache/tomcat/util/buf/B2CConverter.java   | 12 +++++++++++-
 .../apache/tomcat/util/buf/TestB2CConverter.java    | 21 +++++++++++++++++++++
 webapps/docs/changelog.xml                          |  4 ++++
 3 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/java/org/apache/tomcat/util/buf/B2CConverter.java b/java/org/apache/tomcat/util/buf/B2CConverter.java
index d58c49033c..6a461f957e 100644
--- a/java/org/apache/tomcat/util/buf/B2CConverter.java
+++ b/java/org/apache/tomcat/util/buf/B2CConverter.java
@@ -287,10 +287,20 @@ public class B2CConverter {
         }
         // Do the decoding and get the results into the byte chunk and the char
         // chunk
+        int bbStart = bb.position();
         result = decoder.decode(bb, cb, endOfInput);
         if (result.isError()) {
             result.throwException();
-        } else if (result.isOverflow() || result.isUnderflow()) {
+        } else if (result.isOverflow()) {
+            // Propagate current positions to the byte chunk and char chunk
+            bc.position(bb.position());
+            cc.limit(cb.position());
+            if (bb.position() == bbStart && bc.remaining() > 0 && bc.remaining() <= leftovers.array().length) {
+                leftovers.limit(leftovers.array().length);
+                leftovers.position(bc.remaining());
+                bc.get(leftovers.array(), 0, bc.remaining());
+            }
+        } else if (result.isUnderflow()) {
             // Propagate current positions to the byte chunk and char chunk
             bc.position(bb.position());
             cc.limit(cb.position());
diff --git a/test/org/apache/tomcat/util/buf/TestB2CConverter.java b/test/org/apache/tomcat/util/buf/TestB2CConverter.java
index 89a4765244..7108b0cfb2 100644
--- a/test/org/apache/tomcat/util/buf/TestB2CConverter.java
+++ b/test/org/apache/tomcat/util/buf/TestB2CConverter.java
@@ -22,6 +22,7 @@ import java.nio.CharBuffer;
 import java.nio.charset.Charset;
 import java.nio.charset.MalformedInputException;
 import java.nio.charset.StandardCharsets;
+import java.util.Arrays;
 import java.util.Locale;
 
 import org.junit.Assert;
@@ -224,6 +225,26 @@ public class TestB2CConverter {
     }
 
 
+    @Test
+    public void testOverflowWithLargeReadBuffer() throws Exception {
+        // Test range of input sizes from default (8kB) to 12kB.
+        for (int i = 0; i < 4096; i++) {
+            B2CConverter conv = new B2CConverter(StandardCharsets.UTF_8);
+            byte[] bytes = new byte[InputBuffer.DEFAULT_BUFFER_SIZE + i];
+            Arrays.fill(bytes, (byte) '0');
+            ByteBuffer bb = ByteBuffer.wrap(bytes);
+            CharBuffer cb = newCharBuffer(InputBuffer.DEFAULT_BUFFER_SIZE);
+            TesterInputBuffer ib = new TesterInputBuffer(bb);
+
+            conv.convert(bb, cb, ib, false);
+
+            Assert.assertEquals(InputBuffer.DEFAULT_BUFFER_SIZE, cb.remaining());
+            Assert.assertEquals(InputBuffer.DEFAULT_BUFFER_SIZE, bb.position());
+            Assert.assertEquals(bytes.length - InputBuffer.DEFAULT_BUFFER_SIZE, bb.remaining());
+        }
+    }
+
+
     @Test
     public void testLeftoverChunkWithTrailingBytes() throws Exception {
         B2CConverter conv = new B2CConverter(StandardCharsets.UTF_8);
diff --git a/webapps/docs/changelog.xml b/webapps/docs/changelog.xml
index a5383042c8..a3364a7457 100644
--- a/webapps/docs/changelog.xml
+++ b/webapps/docs/changelog.xml
@@ -161,6 +161,10 @@
         not available when the connector is explicitly configured to use Tomcat
         Native with OpenSSL for TLS. (markt)
       </fix>
+      <fix>
+        Correct a regression introduced in 9.0.119 that broke reading of some
+        request bodies via a Reader. (markt)
+      </fix>
     </changelog>
   </subsection>
   <subsection name="Jasper">