Commit 04a2e6a5 authored by Eric W. Biederman's avatar Eric W. Biederman Committed by Linus Torvalds

[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: default avatarEric W. Biederman <ebiederm@xmission.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 8d42db18
...@@ -2990,7 +2990,8 @@ static int tiocgpgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t ...@@ -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) 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); int retval = tty_check_change(real_tty);
if (retval == -EIO) if (retval == -EIO)
...@@ -3001,14 +3002,23 @@ static int tiocspgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t ...@@ -3001,14 +3002,23 @@ static int tiocspgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t
(current->signal->tty != real_tty) || (current->signal->tty != real_tty) ||
(real_tty->session != process_session(current))) (real_tty->session != process_session(current)))
return -ENOTTY; return -ENOTTY;
if (get_user(pgrp, p)) if (get_user(pgrp_nr, p))
return -EFAULT; return -EFAULT;
if (pgrp < 0) if (pgrp_nr < 0)
return -EINVAL; return -EINVAL;
if (session_of_pgrp(pgrp) != process_session(current)) rcu_read_lock();
return -EPERM; pgrp = find_pid(pgrp_nr);
real_tty->pgrp = pgrp; retval = -ESRCH;
return 0; 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;
} }
/** /**
......
...@@ -134,7 +134,8 @@ extern unsigned long long memparse(char *ptr, char **retptr); ...@@ -134,7 +134,8 @@ extern unsigned long long memparse(char *ptr, char **retptr);
extern int core_kernel_text(unsigned long addr); 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 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); extern void dump_thread(struct pt_regs *regs, struct user *dump);
......
...@@ -185,21 +185,19 @@ void release_task(struct task_struct * p) ...@@ -185,21 +185,19 @@ void release_task(struct task_struct * p)
* This checks not only the pgrp, but falls back on the pid if no * 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 * satisfactory pgrp is found. I dunno - gdb doesn't work correctly
* without this... * 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; 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) if (p == NULL)
p = find_task_by_pid(pgrp); p = pid_task(pgrp, PIDTYPE_PID);
if (p != NULL) if (p != NULL)
sid = process_session(p); sid = task_session(p);
read_unlock(&tasklist_lock);
return sid; return sid;
} }
......
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