Comment 9 for bug 1233107

Created attachment 5727
Determine max hostname

In display.c:

#define MAX_HOSTNAME_LENGTH 32

This includes the null byte, so the limit is really 31 characters. The real limit is 64+1 on Linux and 255+1 on BSD.

If the buffer is not big enough for the hostname, gethostname will return ENAMETOOLONG and the hostname will be set to NULL.

Later, when a client is killed, the hostname is tested with strcmp, which causes a segfault.

Example of the bug:

https://bugzilla.redhat.com/show_bug.cgi?id=1085082

If you check the environment file posted, the hostname is 33 characters.

Patch is attached which uses HOST_NAME_MAX to determine the maximum hostname length. If not defined, it is defined to 255. From the gethostname (Linux) man page:

       SUSv2 guarantees that "Host names are limited to 255 bytes".
       POSIX.1-2001 guarantees that "Host names (not including the terminating
       null byte) are limited to HOST_NAME_MAX bytes". On Linux,
       HOST_NAME_MAX is defined with the value 64, which has been the limit
       since Linux 1.0 (earlier kernels imposed a limit of 8 bytes).

The patch also adds a warning if gethostname still fails, and a null check in when the hostname is tested.