Cap wal_buffers to avoid a server crash when it's set very large.

robertmhaas · robertmhaas · commit 369342cf7097 · 2015-08-04T12:58:54.000-04:00
It must be possible to multiply wal_buffers by XLOG_BLCKSZ without
overflowing int, or calculations in StartupXLOG will go badly wrong
and crash the server.  Avoid that by imposing a maximum value on
wal_buffers.  This will be just under 2GB, assuming the usual value
for XLOG_BLCKSZ.

Josh Berkus, per an analysis by Andrew Gierth.
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
@@ -2215,7 +2215,7 @@ static struct config_int ConfigureNamesInt[] =
 			GUC_UNIT_XBLOCKS
 		},
 		&XLOGbuffers,
-		-1, -1, INT_MAX,
+		-1, -1, (INT_MAX / XLOG_BLCKSZ),
 		check_wal_buffers, NULL, NULL
 	},
 
