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[PATCH] pid: make session_of_pgrp use struct pid instead of pid_t

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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>
This commit is contained in:
Eric W. Biederman 2007-02-12 00:52:56 -08:00 committed by Linus Torvalds
parent 8d42db189c
commit 04a2e6a5cb
3 changed files with 26 additions and 17 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

24
drivers/char/tty_io.c
View file

@ -2990,7 +2990,8 @@ static int tiocgpgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t
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 @@ static int tiocspgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t
(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;
}
/**

3
include/linux/kernel.h
View file

@ -134,7 +134,8 @@ extern unsigned long long memparse(char *ptr, char **retptr);
extern int core_kernel_text(unsigned long addr);
extern int __kernel_text_address(unsigned long addr);
extern int kernel_text_address(unsigned long addr);
extern int session_of_pgrp(int pgrp);
struct pid;
extern struct pid *session_of_pgrp(struct pid *pgrp);
extern void dump_thread(struct pt_regs *regs, struct user *dump);

16
kernel/exit.c
View file

@ -185,21 +185,19 @@ repeat:
* This checks not only the pgrp, but falls back on the pid if no
* satisfactory pgrp is found. I dunno - gdb doesn't work correctly
* without this...
*
* The caller must hold rcu lock or the tasklist lock.
*/
int session_of_pgrp(int pgrp)
struct pid *session_of_pgrp(struct pid *pgrp)
{
struct task_struct *p;
int sid = 0;
struct pid *sid = NULL;
read_lock(&tasklist_lock);
p = find_task_by_pid_type(PIDTYPE_PGID, pgrp);
p = pid_task(pgrp, PIDTYPE_PGID);
if (p == NULL)
p = find_task_by_pid(pgrp);
p = pid_task(pgrp, PIDTYPE_PID);
if (p != NULL)
sid = process_session(p);
read_unlock(&tasklist_lock);
sid = task_session(p);
return sid;
}