SegFault in latest main.c::change_winsize

[apedev7]

The function main.c::change_winsize segfault, caused by NULL tty.

This is easily reproducible by symlink /bin/login to a shell script that exits immediately without doing anything.

The underlaying sequence appears to be

1. SIGCHLD queued,
2. The window size message queued
3. SIGCHLD processed to destroy the SID
4. change_winsize is called with the destroyed SID.
5. tty pointer thus is null

[zhaojh329]

Thanks.

[zhaojh329]

Need to check the value of tty, if it is NULL, return directly.

[zhaojh329]

[zhaojh329]

Can you make a PR to fix it?

[apedev7]

I tested your fix, and it works fine.

I'm fine with your pushing the fix into the repo directly; I don't need the credit.