Fix potential crash after constraint violation errors in partitioned tables.

anarazel · anarazel · commit 44170a58092d · 2020-03-23T14:52:18.000-07:00
During the reporting of constraint violations for partitioned tables, ExecPartitionCheckEmitError(), ExecConstraints(), ExecWithCheckOptions() set the slot descriptor of the input slot to the root partition's tuple desc. That's generally problematic when the slot could be used by other routines, but can cause crashes after the introduction of slots with "fixed" tuple descriptors in ad7dbee. The problem likely escaped detection so far for two reasons: First, currently the only known way that these routines are used with a partitioned table that is not "owned" by partitioning code is when "fast defaults" are used for the child partition. Second, as an error is raised afterwards, an "external" slot that had its descriptor changed, is very unlikely to continue being used. Even though the issue currently is only known to cause a crash for 11 (as that has both fast defaults and "fixed" slot descriptors), it seems worth applying the fix to 10 too. Potentially changing random slots is hazardous. Regression tests will be added in a separate commit, as it seems best to add them for master and 12 too. Reported-By: Daniel WM Author: Andres Freund Bug: #16293 Discussion: https://postgr.es/m/16293-26f5777d10143a66@postgresql.org Backpatch: 11, 10 only
diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
@@ -1917,6 +1917,8 @@ ExecPartitionCheck(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 			if (map != NULL)
 			{
 				tuple = do_convert_tuple(tuple, map);
+				/* one off slot for building error message */
+				slot = MakeTupleTableSlot();
 				ExecSetSlotDescriptor(slot, tupdesc);
 				ExecStoreTuple(tuple, slot, InvalidBuffer, false);
 			}
@@ -1995,6 +1997,8 @@ ExecConstraints(ResultRelInfo *resultRelInfo,
 					if (map != NULL)
 					{
 						tuple = do_convert_tuple(tuple, map);
+						/* one off slot for building error message */
+						slot = MakeTupleTableSlot();
 						ExecSetSlotDescriptor(slot, tupdesc);
 						ExecStoreTuple(tuple, slot, InvalidBuffer, false);
 					}
@@ -2043,6 +2047,8 @@ ExecConstraints(ResultRelInfo *resultRelInfo,
 				if (map != NULL)
 				{
 					tuple = do_convert_tuple(tuple, map);
+					/* one off slot for building error message */
+					slot = MakeTupleTableSlot();
 					ExecSetSlotDescriptor(slot, tupdesc);
 					ExecStoreTuple(tuple, slot, InvalidBuffer, false);
 				}
@@ -2153,6 +2159,8 @@ ExecWithCheckOptions(WCOKind kind, ResultRelInfo *resultRelInfo,
 						if (map != NULL)
 						{
 							tuple = do_convert_tuple(tuple, map);
+							/* one off slot for building error message */
+							slot = MakeTupleTableSlot();
 							ExecSetSlotDescriptor(slot, tupdesc);
 							ExecStoreTuple(tuple, slot, InvalidBuffer, false);
 						}

Original file line number	Diff line number	Diff line change
`@@ -1917,6 +1917,8 @@ ExecPartitionCheck(ResultRelInfo resultRelInfo, TupleTableSlot slot,`
`1917`	`1917`	`if (map != NULL)`
`1918`	`1918`	`{`
`1919`	`1919`	`tuple = do_convert_tuple(tuple, map);`
	`1920`	`+ /* one off slot for building error message */`
	`1921`	`+ slot = MakeTupleTableSlot();`
`1920`	`1922`	`ExecSetSlotDescriptor(slot, tupdesc);`
`1921`	`1923`	`ExecStoreTuple(tuple, slot, InvalidBuffer, false);`
`1922`	`1924`	`}`
`@@ -1995,6 +1997,8 @@ ExecConstraints(ResultRelInfo *resultRelInfo,`
`1995`	`1997`	`if (map != NULL)`
`1996`	`1998`	`{`
`1997`	`1999`	`tuple = do_convert_tuple(tuple, map);`
	`2000`	`+ /* one off slot for building error message */`
	`2001`	`+ slot = MakeTupleTableSlot();`
`1998`	`2002`	`ExecSetSlotDescriptor(slot, tupdesc);`
`1999`	`2003`	`ExecStoreTuple(tuple, slot, InvalidBuffer, false);`
`2000`	`2004`	`}`
`@@ -2043,6 +2047,8 @@ ExecConstraints(ResultRelInfo *resultRelInfo,`
`2043`	`2047`	`if (map != NULL)`
`2044`	`2048`	`{`
`2045`	`2049`	`tuple = do_convert_tuple(tuple, map);`
	`2050`	`+ /* one off slot for building error message */`
	`2051`	`+ slot = MakeTupleTableSlot();`
`2046`	`2052`	`ExecSetSlotDescriptor(slot, tupdesc);`
`2047`	`2053`	`ExecStoreTuple(tuple, slot, InvalidBuffer, false);`
`2048`	`2054`	`}`
`@@ -2153,6 +2159,8 @@ ExecWithCheckOptions(WCOKind kind, ResultRelInfo *resultRelInfo,`
`2153`	`2159`	`if (map != NULL)`
`2154`	`2160`	`{`
`2155`	`2161`	`tuple = do_convert_tuple(tuple, map);`
	`2162`	`+ /* one off slot for building error message */`
	`2163`	`+ slot = MakeTupleTableSlot();`
`2156`	`2164`	`ExecSetSlotDescriptor(slot, tupdesc);`
`2157`	`2165`	`ExecStoreTuple(tuple, slot, InvalidBuffer, false);`
`2158`	`2166`	`}`