postgres.git / summary / log / commit / refs

commit    02e20bb2dcaa523782a8fe7de1c2ddfefaeff033
Author:   Alvaro Herrera <alvherre@alvh.no-ip.org>
Date:     Fri Nov 05 15:29:35 2021 +0000

    Avoid crash in rare case of concurrent DROP
    
    When a role being dropped contains is referenced by catalog objects that
    are concurrently also being dropped, a crash can result while trying to
    construct the string that describes the objects.  Suppress that by
    ignoring objects whose descriptions are returned as NULL.
    
    The majority of relevant codesites were already cautious about this
    already; we had just missed a couple.
    
    This is an old bug, so backpatch all the way back.
    
    Reported-by: Alexander Lakhin <exclusion@gmail.com>
    Discussion: https://postgr.es/m/17126-21887f04508cb5c8@postgresql.org


 src/backend/catalog/dependency.c  | 31 ++++++++++++++++++++-----------
 src/backend/catalog/pg_shdepend.c |  6 ++++++
 2 files changed, 26 insertions(+), 11 deletions(-)

diff --git a/src/backend/catalog/dependency.c b/src/backend/catalog/dependency.c
index 85b2bbac024..52376949973 100644
--- a/src/backend/catalog/dependency.c
+++ b/src/backend/catalog/dependency.c
@@ -1102,6 +1102,10 @@ reportDependentObjects(const ObjectAddresses *targetObjects,
 
 		objDesc = getObjectDescription(obj, false);
 
+		/* An object being dropped concurrently doesn't need to be reported */
+		if (objDesc == NULL)
+			continue;
+
 		/*
 		 * If, at any stage of the recursive search, we reached the object via
 		 * an AUTO, INTERNAL, PARTITION, or EXTENSION dependency, then it's
@@ -1127,23 +1131,28 @@ reportDependentObjects(const ObjectAddresses *targetObjects,
 			char	   *otherDesc = getObjectDescription(&extra->dependee,
 														 false);
 
-			if (numReportedClient < MAX_REPORTED_DEPS)
+			if (otherDesc)
 			{
+				if (numReportedClient < MAX_REPORTED_DEPS)
+				{
+					/* separate entries with a newline */
+					if (clientdetail.len != 0)
+						appendStringInfoChar(&clientdetail, '\n');
+					appendStringInfo(&clientdetail, _("%s depends on %s"),
+									 objDesc, otherDesc);
+					numReportedClient++;
+				}
+				else
+					numNotReportedClient++;
 				/* separate entries with a newline */
-				if (clientdetail.len != 0)
-					appendStringInfoChar(&clientdetail, '\n');
-				appendStringInfo(&clientdetail, _("%s depends on %s"),
+				if (logdetail.len != 0)
+					appendStringInfoChar(&logdetail, '\n');
+				appendStringInfo(&logdetail, _("%s depends on %s"),
 								 objDesc, otherDesc);
-				numReportedClient++;
+				pfree(otherDesc);
 			}
 			else
 				numNotReportedClient++;
-			/* separate entries with a newline */
-			if (logdetail.len != 0)
-				appendStringInfoChar(&logdetail, '\n');
-			appendStringInfo(&logdetail, _("%s depends on %s"),
-							 objDesc, otherDesc);
-			pfree(otherDesc);
 			ok = false;
 		}
 		else
diff --git a/src/backend/catalog/pg_shdepend.c b/src/backend/catalog/pg_shdepend.c
index d0c96b6de1d..d89a9fa2bfc 100644
--- a/src/backend/catalog/pg_shdepend.c
+++ b/src/backend/catalog/pg_shdepend.c
@@ -1238,6 +1238,12 @@ storeObjectDescription(StringInfo descs,
 {
 	char	   *objdesc = getObjectDescription(object, false);
 
+	/*
+	 * An object being dropped concurrently doesn't need to be reported.
+	 */
+	if (objdesc == NULL)
+		return;
+
 	/* separate entries with a newline */
 	if (descs->len != 0)
 		appendStringInfoChar(descs, '\n');


[parent: c829fbc3dc93]