segfault and uid problem

Hi!

I'm running FreeBSD/amd64 and when running a screen inside a screen it 
used
segfault immediatly, .i.e.
user hscholz starts screen, su -m to root, screen -> segfault

(gdb) bt
#0  0x0000000200a7e868 in strncpy () from /lib/libc.so.5
#1  0x000000000040579e in Msg (err=2, fmt=0x7fffffffc7ca "") at 
screen.c:1909
#2  0x0000000000414945 in MakeClientSocket (err=1) at socket.c:473
#3  0x00000000004149e1 in SendCreateMsg (
     sty=0x7d5 <Address 0x7d5 out of bounds>, nwin=0x7fffffffe140)
     at socket.c:621
#4  0x00000000004045f3 in main (ac=493, av=0x7fffffffe4a0) at 
screen.c:1124
(gdb)

Reading the make output and the strncpy/strerror manpages it becomes 
pretty
much evident that string.h has to be included:

--- screen.c.orig       Sun Feb 15 14:49:28 2004
+++ screen.c    Sun Feb 15 14:50:16 2004
@@ -35,6 +35,10 @@

  #include <fcntl.h>

+#ifdef __FreeBSD__
+#include <string.h>
+#endif
+
  #ifdef sgi
  # include <sys/sysmacros.h>
  #endif
@@ -1906,7 +1910,7 @@
        p += strlen(p);
        *p++ = ':';
        *p++ = ' ';
-      strncpy(p, strerror(err), buf + sizeof(buf) - p - 1);
+      strncpy(p, (char *)strerror(err), buf + sizeof(buf) - p - 1);
        buf[sizeof(buf) - 1] = 0;
      }
    debug2("Msg('%s') (%#x);\n", buf, (unsigned int)display);
@@ -1960,7 +1964,7 @@
        p += strlen(p);
        *p++ = ':';
        *p++ = ' ';
-      strncpy(p, strerror(err), buf + sizeof(buf) - p - 1);
+      strncpy(p, (char *)strerror(err), buf + sizeof(buf) - p - 1);
        buf[sizeof(buf) - 1] = 0;
      }
    debug3("Panic('%s'); display=%x displays=%x\n", buf, display, 
displays);

Same is true for layer.c:

--- layer.c.orig        Sun Feb 15 14:51:35 2004
+++ layer.c     Sun Feb 15 14:51:57 2004
@@ -23,6 +23,10 @@

  #include <sys/types.h>

+#ifdef __FreeBSD__
+#include <string.h>
+#endif
+
  #include "config.h"
  #include "screen.h"
  #include "mark.h"
@@ -1097,7 +1101,7 @@
        p += strlen(p);
        *p++ = ':';
        *p++ = ' ';
-      strncpy(p, strerror(err), buf + sizeof(buf) - p - 1);
+      strncpy(p, (char *)strerror(err), buf + sizeof(buf) - p - 1);
        buf[sizeof(buf) - 1] = 0;
      }
    debug2("LMsg('%s') (%#x);\n", buf, (unsigned int)flayer);

This is only needed on 64Bit FreeBSD platform as I couldn't get screen
on a i386 box to segfault but the includes are valid for both.

Once correctly patched screen doesn't core dump but prints:
[0.20] root@slurmcan:~ > screen
/tmp/screens/S-root/89382.ttyp3.slurmcan: No such file or directory
[0.20] root@slurmcan:~ >

[0.11] root@slurmcan:/tmp/screens > find . -type p
./S-hscholz/89382.ttyp3.slurmcan
[0.10] root@slurmcan:/tmp/screens >

Well, this looks like a uid vs. euid problem but let's investigate.
I did su -m which sets my uid to 0 but keeps my environment variables.
Ok, now let's use su - instead of su -m ... et voila screen works:

[0.10] root@slurmcan:/tmp/screens > find . -type p
./S-root/89869.ttyp4.slurmcan
./S-hscholz/89382.ttyp3.slurmcan
[0.04] root@slurmcan:/tmp/screens >

Since I don't want to read all the char *LoginName related code
and you definitly know better how to deal with this (beside the fact
that I'm hungry :)) I'll stop here.

In case someone needs access to the box or wants me to test code feel
free to send me a private mail.

Hendrik

-- 
Hendrik Scholz - [email protected] - http://www.raisdorf.net/
cell phone: 404-606-5324 (US) 0160-1570-272 (DE)



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