From: Linux Karlsson <karlsson@ntp.org>
Date: Wed, 20 Jul 2011 11:06:51 +0000 (+0200)
Subject: [BUG 1970] UNLINK_EXPR_SLIST() causes crash if list is empty.
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c10c13d58607eabb3f80792abd9e955f87b290b2;p=thirdparty%2Fntp.git

[BUG 1970] UNLINK_EXPR_SLIST() causes crash if list is empty.

bk: 4e26b6cb6pcvXvx-_kT_qz-rTfCKVw
---

diff --git a/ChangeLog b/ChangeLog
index 802b75d932..360a5e809a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,6 @@
 ---
 
+* [Bug 1970] UNLINK_EXPR_SLIST() causes crash if list is empty.
 * [Bug 1961] html2man update: distribute ntp-wait.html.
 
 ---
diff --git a/include/ntp_lists.h b/include/ntp_lists.h
index ee3f9c2995..6079b83a92 100644
--- a/include/ntp_lists.h
+++ b/include/ntp_lists.h
@@ -42,7 +42,7 @@
  *	unlink entry where expression expr is nonzero.  expr can refer
  *	to the entry being tested using UNLINK_EXPR_SLIST_CURRENT(),
  *	alias U_E_S_CUR().  See the implementation of UNLINK_SLIST()
- *	below for an example.
+ *	below for an example. U_E_S_CUR() is NULL iff the list is empty.
  *	punlinked is pointed to the removed entry or NULL if none
  *	satisfy expr.
  *
@@ -126,9 +126,10 @@ do {								\
 	ppentry = &(listhead);					\
 								\
 	while (!(expr))						\
-		if ((*ppentry)->nextlink != NULL)		\
+		if ((*ppentry) != NULL &&			\
+		    (*ppentry)->nextlink != NULL) {		\
 			ppentry = &((*ppentry)->nextlink);	\
-		else {						\
+		} else {						\
 			ppentry = NULL;				\
 			break;					\
 		}						\