From a7812eb4bec402423c2e8bc5a6a683d5e9191548 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Fri, 6 Jan 2006 02:58:25 +0000
Subject: [PATCH] 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.
---
src/backend/postmaster/postmaster.c | 17 +++++++++++++++--
1 file changed, 15 insertions(+), 2 deletions(-)
diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index 31d370ebbb2..43deb57aa2c 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -37,7 +37,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.478 2006/01/05 10:07:45 petere Exp $
+ * $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.479 2006/01/06 02:58:25 tgl Exp $
*
* NOTES
*
@@ -147,7 +147,11 @@ 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
@@ -3083,6 +3087,15 @@ 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);
--
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