Re: um: TTY fixes (?)
From: Alan Cox
Date: Tue Jun 05 2012 - 07:12:13 EST
> open_tty() closes all the old file descriptors after tty open:
It needs to close them before.
>
> vhangup();
> ...
> fd = open(tty, O_RDWR | O_NONBLOCK);
> ...
>
> flags = fcntl(fd, F_GETFL);
> flags &= ~O_NONBLOCK;
> fcntl(fd, F_SETFL, flags);
>
> for (i = 0; i < fd; i++)
> close(i);
> for (i = 0; i < 3; i++)
> if (fd != i)
> dup2(fd, i);
> if (fd >= 3)
> close(fd);
>
> we use this for pretty long time (17+ years).
>
> > If I add:
> > fclose(stdin);
> > fclose(stdout);
> > fclose(stderr);
> > before the call to vhangup() login works like charm. :-)
> >
> > Karel, what do you think?
>
> It's probably no problem to close all the file descriptors before
> vhangup(), but it would be nice to know why we need this change after
> 20 years :-)
Because we want to actually fix the standards (and security) violation
that means it has happened to work on the console for 20 years.
Actually I'd prefer a clever solution which can spot all the fds are the
same process so we can keep compatibility but I've not found a sensible
way to do that.
Alan
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