Always read returnvalue from stat calls

{f}stat() can fail and reading the stat buffer without checking for
status is bad hygiene. Ensure to always test return value and take
the appropriate error path in case of stat error.

contrib/pg_upgrade/oid_dump.c

@@ -222,7 +222,9 @@ slurp_oid_files(migratorContext *ctx)
 	if (!oid_dump)
 		pg_log(ctx, PG_FATAL, "Could not open necessary file:  %s\n", GLOBAL_OIDS_DUMP_FILE);
 
-	fstat(fileno(oid_dump), &st);
+	if (fstat(fileno(oid_dump), &st) != 0)
+		pg_log(ctx, PG_FATAL, "Could not read file \"%s\": %s\n",
+			   GLOBAL_OIDS_DUMP_FILE, strerror(errno));
 
 	reserved_oids = pg_malloc(ctx, st.st_size + 1);
 	fread(reserved_oids, st.st_size, 1, oid_dump);
@@ -241,7 +243,9 @@ slurp_oid_files(migratorContext *ctx)
 		if (!oid_dump)
 			pg_log(ctx, PG_FATAL, "Could not open necessary file:  %s\n", filename);
 
-		fstat(fileno(oid_dump), &st);
+		if (fstat(fileno(oid_dump), &st) != 0)
+			pg_log(ctx, PG_FATAL, "Could not read file \"%s\": %s\n",
+				   filename, strerror(errno));
 
 		reserved_oids = pg_malloc(ctx, st.st_size + 1);
 		fread(reserved_oids, st.st_size, 1, oid_dump);

src/backend/cdb/cdbfilerepmirror.c

@@ -2468,8 +2468,7 @@ FileRepMirror_DropFilesFromDir(FileName fileName)
 			{
 				if (errno == EPERM)
 				{
-					stat(path, &st);
-					if (S_ISDIR(st.st_mode))
+					if ((stat(path, &st) >= 0) && (S_ISDIR(st.st_mode)))
 						continue;
 				}