[PATCH] pid: make session_of_pgrp use struct pid instead of pid_t
To properly implement a pid namespace I need to deal exclusively in terms of
struct pid, because pid_t values become ambiguous.
To this end session_of_pgrp is transformed to take and return a struct pid
pointer. To avoid the need to worry about reference counting I now require my
caller to hold the appropriate locks. Leaving callers repsonsible for
increasing the reference count if they need access to the result outside of
the locks.
Since session_of_pgrp currently only has one caller and that caller simply
uses only test the result for equality with another process group, the locking
change means I don't actually have to acquire the tasklist_lock at all.
tiocspgrp is also modified to take and release the lock. The logic there is a
little more complicated but nothing I won't need when I convert pgrp of a tty
to a struct pid pointer.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index abfe24d..95f3596 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -2990,7 +2990,8 @@
static int tiocspgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t __user *p)
{
- pid_t pgrp;
+ struct pid *pgrp;
+ pid_t pgrp_nr;
int retval = tty_check_change(real_tty);
if (retval == -EIO)
@@ -3001,14 +3002,23 @@
(current->signal->tty != real_tty) ||
(real_tty->session != process_session(current)))
return -ENOTTY;
- if (get_user(pgrp, p))
+ if (get_user(pgrp_nr, p))
return -EFAULT;
- if (pgrp < 0)
+ if (pgrp_nr < 0)
return -EINVAL;
- if (session_of_pgrp(pgrp) != process_session(current))
- return -EPERM;
- real_tty->pgrp = pgrp;
- return 0;
+ rcu_read_lock();
+ pgrp = find_pid(pgrp_nr);
+ retval = -ESRCH;
+ if (!pgrp)
+ goto out_unlock;
+ retval = -EPERM;
+ if (session_of_pgrp(pgrp) != task_session(current))
+ goto out_unlock;
+ retval = 0;
+ real_tty->pgrp = pgrp_nr;
+out_unlock:
+ rcu_read_unlock();
+ return retval;
}
/**