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Kernel: Store TTY's foreground process as a WeakPtr<Process>

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This ensures that we don't leave a stale PGID assigned to the TTY after
the process exits, which would make PID recycling attacks possible.
This commit is contained in:
Andreas Kling 2020-08-06 11:17:53 +02:00
parent ff01cfa08a
commit ddab7ab693
3 changed files with 22 additions and 12 deletions
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16
Kernel/TTY/TTY.cpp
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@ -155,9 +155,9 @@ void TTY::emit(u8 ch)
if (ch == m_termios.c_cc[VSUSP]) {
dbg() << tty_name() << ": VSUSP pressed!";
generate_signal(SIGTSTP);
if (auto process = Process::from_pid(m_pgid)) {
if (auto parent = Process::from_pid(process->ppid()))
(void)parent->send_signal(SIGCHLD, process);
if (m_process) {
if (auto parent = Process::from_pid(m_process->ppid()))
(void)parent->send_signal(SIGCHLD, m_process);
}
return;
}
@ -304,7 +304,7 @@ int TTY::ioctl(FileDescription&, unsigned request, FlatPtr arg)
#endif
switch (request) {
case TIOCGPGRP:
return m_pgid;
return this->pgid();
case TIOCSPGRP:
pgid = static_cast<pid_t>(arg);
if (pgid <= 0)
@ -318,8 +318,8 @@ int TTY::ioctl(FileDescription&, unsigned request, FlatPtr arg)
return -EPERM;
if (current_process.sid() != process->sid())
return -EPERM;
m_process = process->make_weak_ptr();
}
m_pgid = pgid;
return 0;
case TCGETS: {
user_termios = reinterpret_cast<termios*>(arg);
@ -394,4 +394,10 @@ void TTY::hang_up()
{
generate_signal(SIGHUP);
}
pid_t TTY::pgid() const
{
return m_process ? m_process->pgid() : 0;
}
}