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SubjectRe: heavy handed exit() in latest BK

On Sun, 9 Feb 2003, Roland McGrath wrote:

> > - session-IDs and group-IDs are set outside the tasklist lock. This
> > causes breakage in the USB code. The correct fix is to do this:
>
> This is outside the part of the code that I've touched lately.

yes, i introduced the bug with the new pidhash. Here's the fix, against
BK-curr.

Ingo

--- linux/include/linux/sched.h.orig
+++ linux/include/linux/sched.h
@@ -503,6 +503,8 @@
extern struct mm_struct init_mm;

extern struct task_struct *find_task_by_pid(int pid);
+extern void set_special_pids(pid_t session, pid_t pgrp);
+extern void __set_special_pids(pid_t session, pid_t pgrp);

/* per-UID process charging. */
extern struct user_struct * alloc_uid(uid_t);
--- linux/fs/jffs/intrep.c.orig
+++ linux/fs/jffs/intrep.c
@@ -3344,8 +3344,7 @@
lock_kernel();
exit_mm(c->gc_task);

- current->session = 1;
- current->pgrp = 1;
+ set_special_pids(1, 1);
init_completion(&c->gc_thread_comp); /* barrier */
spin_lock_irq(&current->sighand->siglock);
siginitsetinv (&current->blocked, sigmask(SIGHUP) | sigmask(SIGKILL) | sigmask(SIGSTOP) | sigmask(SIGCONT));
--- linux/kernel/exit.c.orig
+++ linux/kernel/exit.c
@@ -254,6 +254,29 @@
write_unlock_irq(&tasklist_lock);
}

+void __set_special_pids(pid_t session, pid_t pgrp)
+{
+ struct task_struct *curr = current;
+
+ if (curr->session != session) {
+ detach_pid(curr, PIDTYPE_SID);
+ curr->session = session;
+ attach_pid(curr, PIDTYPE_SID, session);
+ }
+ if (curr->pgrp != pgrp) {
+ detach_pid(curr, PIDTYPE_PGID);
+ curr->pgrp = pgrp;
+ attach_pid(curr, PIDTYPE_PGID, pgrp);
+ }
+}
+
+void set_special_pids(pid_t session, pid_t pgrp)
+{
+ write_lock_irq(&tasklist_lock);
+ __set_special_pids(session, pgrp);
+ write_unlock_irq(&tasklist_lock);
+}
+
/*
* Put all the gunge required to become a kernel thread without
* attached user resources in one place where it belongs.
@@ -271,8 +294,7 @@
*/
exit_mm(current);

- current->session = 1;
- current->pgrp = 1;
+ set_special_pids(1, 1);
current->tty = NULL;

/* Become as one with the init task */
--- linux/kernel/kmod.c.orig
+++ linux/kernel/kmod.c
@@ -100,8 +100,7 @@
int i;
struct task_struct *curtask = current;

- curtask->session = 1;
- curtask->pgrp = 1;
+ set_special_pids(1, 1);

use_init_fs_context();

--- linux/kernel/sys.c.orig
+++ linux/kernel/sys.c
@@ -1021,16 +1021,7 @@
goto out;

current->leader = 1;
- if (current->session != current->pid) {
- detach_pid(current, PIDTYPE_SID);
- current->session = current->pid;
- attach_pid(current, PIDTYPE_SID, current->pid);
- }
- if (current->pgrp != current->pid) {
- detach_pid(current, PIDTYPE_PGID);
- current->pgrp = current->pid;
- attach_pid(current, PIDTYPE_PGID, current->pid);
- }
+ __set_special_pids(current->pid, current->pid);
current->tty = NULL;
current->tty_old_pgrp = 0;
err = current->pgrp;
-
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