kissnetd: Fix possible buffer overflow.

When printing an error message for configurations using particularly
long file names a buffer overflow may occur potencially resulting in
malfunction or crash.

This fixes the following GCC 7.1.1 warnings:

gcc -DHAVE_CONFIG_H -I. -I..  -D_GNU_SOURCE -DAX25_SYSCONFDIR=\""/usr/local/etc/ax25/"\" -DAX25_LOCALSTATEDIR=\""/us
r/local/var/ax25/"\"   -g -O2 -Wall -MT kissnetd.o -MD -MP -MF .deps/kissnetd.Tpo -c -o kissnetd.o kissnetd.c
kissnetd.c: In function ‘main’:
kissnetd.c:124:38: warning: ‘%s’ directive writing up to 4095 bytes into a region of size 66 [-Wformat-overflow=]
     sprintf(MyString, "cannot reopen %s", PortList[PortNumber]->Name);
                                      ^~
kissnetd.c:124:5: note: ‘sprintf’ output between 15 and 4110 bytes into a destination of size 80
     sprintf(MyString, "cannot reopen %s", PortList[PortNumber]->Name);
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kissnetd.c:143:49: warning: ‘%s’ directive writing up to 4095 bytes into a region of size 55 [-Wformat-overflow=]
     sprintf(MyString, "Cannot unlock pts-device %s\n", PortList[PortNumber]->namepts);
                                                 ^~
kissnetd.c:143:5: note: ‘sprintf’ output between 27 and 4122 bytes into a destination of size 80
     sprintf(MyString, "Cannot unlock pts-device %s\n", PortList[PortNumber]->namepts);
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kissnetd.c:154:50: warning: ‘%s’ directive writing up to 4095 bytes into a region of size 54 [-Wformat-overflow=]
     sprintf(MyString, "cannot reopen ptmx (slave %s).", PortList[PortNumber]->namepts);
                                                  ^~
kissnetd.c:154:5: note: ‘sprintf’ output between 29 and 4124 bytes into a destination of size 80
     sprintf(MyString, "cannot reopen ptmx (slave %s).", PortList[PortNumber]->namepts);
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/kiss/kissnetd.c b/kiss/kissnetd.c
index e8448ef..abf9ee9 100644
--- a/kiss/kissnetd.c
+++ b/kiss/kissnetd.c
@@ -106,7 +106,8 @@ static void NewPort(char *Name)
 
 static void ReopenPort(int PortNumber)
 {
-	char MyString[80];
+	char MyString[28 + PATH_MAX];
+
 	PortList[PortNumber]->TimeLastOpen = time(NULL);
 
 	if (VerboseMode) {