Description Vasil Dimov 2006-04-11 07:40:13 UTC

# ngrep
Segmentation fault: 11 (core dumped)
#

# gdb ./ngrep
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This GDB was configured as "amd64-marcel-freebsd"...
(gdb) r
Starting program: /usr/ports/net/ngrep/work/ngrep-1.44/ngrep

Program received signal SIGSEGV, Segmentation fault.
0x0000000800823ed0 in strlen () from /lib/libc.so.6
(gdb) bt
#0  0x0000000800823ed0 in strlen () from /lib/libc.so.6
#1  0x0000000800821521 in __vfprintf () from /lib/libc.so.6
#2  0x000000080082225f in vfprintf () from /lib/libc.so.6
#3  0x000000080080f09a in printf () from /lib/libc.so.6
#4  0x0000000000401f5d in main (argc=1, argv=0x7fffffffeab0) at ngrep.c:355
(gdb) f 4
#4  0x0000000000401f5d in main (argc=1, argv=0x7fffffffeab0) at ngrep.c:355
355                     printf(" (%s/", inet_ntoa(net));
(gdb) l
350             }
351
352             if (quiet < 2) {
353                 printf("interface: %s", dev);
354                 if (net.s_addr && mask.s_addr) {
355                     printf(" (%s/", inet_ntoa(net));
356                     printf("%s)", inet_ntoa(mask));
357                 }
358                 printf("\n");
359             }
(gdb) ins net
$1 = {s_addr = 698560}
(gdb)

So inet_ntoa(net) returns something bogus.

If I modify the code like this:
            char *n;
            n = inet_ntoa(net);
            if (net.s_addr && mask.s_addr) {
                printf(" (%s/", n);
then I get this warning during compilation:

ngrep.c:355: warning: assignment makes pointer from integer without a cast

and gdb shows the following:
...
Program received signal SIGSEGV, Segmentation fault.
0x0000000800823ed0 in strlen () from /lib/libc.so.6
(gdb) f 4
#4  0x0000000000401f65 in main (argc=1, argv=0x7fffffffeab0) at ngrep.c:357
357                     printf(" (%s/", n);
(gdb) ins n
$1 = 0x951530 <Error reading address 0x951530: Bad address>
(gdb)

Fix: Include the appropriate headers as documented in inet_ntoa(3):
http://www.freebsd.org/cgi/man.cgi?query=inet_ntoa



-- 
Vasil Dimov
gro.DSBeerF@dv

Testing can show the presence of bugs, but not their absence.
                -- Edsger W. Dijkstra--0WMuYOD4Xu6P0K7IeNb3BhLADzNyVdOD6YF6gGOueOaWP8f2
Content-Type: text/plain; name="patch-ngrep.c"
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment; filename="patch-ngrep.c"

--- ngrep.c.orig	Tue Apr 11 09:20:31 2006
+++ ngrep.c	Tue Apr 11 09:20:59 2006
@@ -15,6 +15,7 @@
 #include <netinet/in.h>
 #include <netinet/in_systm.h>
 #include <net/if.h>
+#include <arpa/inet.h>
 #include <sys/tty.h>
 #include <pwd.h>
 #endif
How-To-Repeat: 
Just start ngrep on amd64