Fix segfault

src/IO/PeekableReadBuffer.cpp

@@ -82,6 +82,7 @@ bool PeekableReadBuffer::peekNext()
         checkpoint.emplace(memory.data());
         checkpoint_in_own_memory = true;
     }
+
     if (currentlyReadFromOwnMemory())
     {
         /// Update buffer size
@@ -99,7 +100,6 @@ bool PeekableReadBuffer::peekNext()
                 pos_offset = 0;
         }
         BufferBase::set(memory.data(), peeked_size + bytes_to_copy, pos_offset);
-
     }
 
     peeked_size += bytes_to_copy;
@@ -113,12 +113,21 @@ void PeekableReadBuffer::rollbackToCheckpoint(bool drop)
 {
     checkStateCorrect();
 
-    if (!checkpoint)
-        throw DB::Exception("There is no checkpoint", ErrorCodes::LOGICAL_ERROR);
-    else if (checkpointInOwnMemory() == currentlyReadFromOwnMemory())
+    assert(checkpoint);
+
+    if (checkpointInOwnMemory() == currentlyReadFromOwnMemory())
+    {
+        /// Both checkpoint and position are in the same buffer.
         pos = *checkpoint;
-    else /// Checkpoint is in own memory and pos is not. Switch to reading from own memory
+    }
+    else
+    {
+        /// Checkpoint is in own memory and position is not.
+        assert(checkpointInOwnMemory());
+
+        /// Switch to reading from own memory.
         BufferBase::set(memory.data(), peeked_size, *checkpoint - memory.data());
+    }
 
     if (drop)
         dropCheckpoint();
@@ -134,10 +143,11 @@ bool PeekableReadBuffer::nextImpl()
 
     checkStateCorrect();
     bool res;
+    bool checkpoint_at_end = checkpoint && *checkpoint == working_buffer.end();
 
     if (checkpoint)
     {
-        if (currentlyReadFromOwnMemory())
+        if (currentlyReadFromOwnMemory() || checkpoint_at_end)
             res = sub_buf.hasPendingData() || sub_buf.next();
         else
             res = peekNext();
@@ -163,6 +173,13 @@ bool PeekableReadBuffer::nextImpl()
     BufferBase::set(sub_working.begin(), sub_working.size(), sub_buf.offset());
     nextimpl_working_buffer_offset = sub_buf.offset();
 
+    if (checkpoint_at_end)
+    {
+        checkpoint.emplace(working_buffer.begin());
+        peeked_size = 0;
+        checkpoint_in_own_memory = false;
+    }
+
     checkStateCorrect();
     return res;
 }

src/IO/PeekableReadBuffer.h

@@ -43,10 +43,7 @@ public:
     /// Forget checkpoint and all data between checkpoint and position
     ALWAYS_INLINE inline void dropCheckpoint()
     {
-#ifndef NDEBUG
-        if (!checkpoint)
-            throw DB::Exception("There is no checkpoint", ErrorCodes::LOGICAL_ERROR);
-#endif
+        assert(checkpoint);
         if (!currentlyReadFromOwnMemory())
         {
             /// Don't need to store unread data anymore

src/Interpreters/InterserverIOHandler.h

@@ -9,8 +9,6 @@
 #include <Common/ActionBlocker.h>
 #include <common/types.h>
 
-#include <Poco/Net/HTMLForm.h>
-
 #include <atomic>
 #include <map>
 #include <shared_mutex>

src/Server/HTTP/HTMLForm.cpp

@@ -369,6 +369,11 @@ bool HTMLForm::MultipartReadBuffer::nextImpl()
     else
         boundary_hit = startsWith(line, boundary);
 
+    if (!line.empty())
+        /// If we don't make sure that memory is contiguous then situation may happen, when part of the line is inside internal memory
+        /// and other part is inside sub-buffer, thus we'll be unable to setup our working buffer properly.
+        in.makeContinuousMemoryFromCheckpointToPos();
+
     in.rollbackToCheckpoint(true);
 
     /// Rolling back to checkpoint may change underlying buffers.