projects/linux·commit 61bce0f1

pid: generalize task_active_pid_ns

61bce0f1 · Eric W. Biederman <[email protected]> · 2009-01-07 18:08:49 -08:00

Currently task_active_pid_ns is not safe to call after a task becomes a
zombie and exit_task_namespaces is called, as nsproxy becomes NULL.  By
reading the pid namespace from the pid of the task we can trivially solve
this problem at the cost of one extra memory read in what should be the
same cacheline as we read the namespace from.

When moving things around I have made task_active_pid_ns out of line
because keeping it in pid_namespace.h would require adding includes of
pid.h and sched.h that I don't think we want.

This change does make task_active_pid_ns unsafe to call during
copy_process until we attach a pid on the task_struct which seems to be a
reasonable trade off.

Signed-off-by: Eric W. Biederman <[email protected]>
Signed-off-by: Sukadev Bhattiprolu <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: Roland McGrath <[email protected]>
Cc: Bastian Blank <[email protected]>
Cc: Pavel Emelyanov <[email protected]>
Cc: Nadia Derbey <[email protected]>
Acked-by: Serge Hallyn <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Commit
61bce0f1371cfff497fe85594fd39d1a0b15ebe1
Parents
f9fb860f

Changes

3 files changed · +9 −7

FileStatusAddDelContent
include/linux/pid_namespace.hmodified+1−5View file
kernel/fork.cmodified+2−2View file
kernel/pid.cmodified+6−0View file

include/linux/pid_namespace.h

View file
diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
index d82fe82..38d1032 100644
--- a/include/linux/pid_namespace.h
+++ b/include/linux/pid_namespace.h
@@ -79,11 +79,7 @@ static inline void zap_pid_ns_processes(struct pid_namespace *ns)
}
#endif /* CONFIG_PID_NS */
-static inline struct pid_namespace *task_active_pid_ns(struct task_struct *tsk)
-{
- return tsk->nsproxy->pid_ns;
-}
-
+extern struct pid_namespace *task_active_pid_ns(struct task_struct *tsk);
void pidhash_init(void);
void pidmap_init(void);

kernel/fork.c

View file
diff --git a/kernel/fork.c b/kernel/fork.c
index 7b8f2a7..4018308 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1126,12 +1126,12 @@ static struct task_struct *copy_process(unsigned long clone_flags,
if (pid != &init_struct_pid) {
retval = -ENOMEM;
- pid = alloc_pid(task_active_pid_ns(p));
+ pid = alloc_pid(p->nsproxy->pid_ns);
if (!pid)
goto bad_fork_cleanup_io;
if (clone_flags & CLONE_NEWPID) {
- retval = pid_ns_prepare_proc(task_active_pid_ns(p));
+ retval = pid_ns_prepare_proc(p->nsproxy->pid_ns);
if (retval < 0)
goto bad_fork_free_pid;
}

kernel/pid.c

View file
diff --git a/kernel/pid.c b/kernel/pid.c
index af9224c..1b3586f 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -474,6 +474,12 @@ pid_t task_session_nr_ns(struct task_struct *tsk, struct pid_namespace *ns)
}
EXPORT_SYMBOL(task_session_nr_ns);
+struct pid_namespace *task_active_pid_ns(struct task_struct *tsk)
+{
+ return ns_of_pid(task_pid(tsk));
+}
+EXPORT_SYMBOL_GPL(task_active_pid_ns);
+
/*
* Used by proc to find the first pid that is greater than or equal to nr.
*