From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Fri, 6 Jan 2006 02:58:40 +0000 (+0000)
Subject: Fix Windows-only postmaster code to reject a connection request and continue,
X-Git-Url: http://git.postgresql.org/gitweb/static/gitweb.js?a=commitdiff_plain;h=d7dc3220812e49bf6e487f0099ae6632275fe0b7;p=users%2Fbernd%2Fpostgres.git

Fix Windows-only postmaster code to reject a connection request and continue,
rather than elog(FATAL), when there is no more room in ShmemBackendArray.
This is a security issue since too many connection requests arriving close
together could cause the postmaster to shut down, resulting in denial of
service.  Reported by Yoshiyuki Asaba, fixed by Magnus Hagander.
---

diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index 5cfacd173d..afd861b5ca 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -144,7 +144,11 @@ typedef struct bkend
 static Dllist *BackendList;
 
 #ifdef EXEC_BACKEND
-#define NUM_BACKENDARRAY_ELEMS (2*MaxBackends)
+/* 
+ * Number of entries in the backend table. Twice the number of backends,
+ * plus four other subprocesses (stats, bgwriter, autovac, logger). 
+ */
+#define NUM_BACKENDARRAY_ELEMS (2*MaxBackends + 4)
 static Backend *ShmemBackendArray;
 #endif
 
@@ -3018,6 +3022,15 @@ internal_forkexec(int argc, char *argv[], Port *port)
 	Assert(strncmp(argv[1], "-fork", 5) == 0);
 	Assert(argv[2] == NULL);
 
+	/* Verify that there is room in the child list */
+	if (win32_numChildren >= NUM_BACKENDARRAY_ELEMS)
+	{
+		elog(LOG, "no room for child entry in backend list");
+		/* Report same error as for a fork failure on Unix */
+		errno = EAGAIN;
+		return -1;
+	}
+
 	/* Set up shared memory for parameter passing */
 	ZeroMemory(&sa,sizeof(sa));
 	sa.nLength = sizeof(sa);