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pid namespaces: initialize the namespace's proc_mnt

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The namespace's proc_mnt must be kern_mount-ed to make this pointer always
valid, independently of whether the user space mounted the proc or not.  This
solves raced in proc_flush_task, etc.  with the proc_mnt switching from NULL
to not-NULL.

The initialization is done after the init's pid is created and hashed to make
proc_get_sb() finr it and get for root inode.

Sice the namespace holds the vfsmnt, vfsmnt holds the superblock and the
superblock holds the namespace we must explicitly break this circle to destroy
all the stuff.  This is done after the init of the namespace dies.  Running a
few steps forward - when init exits it will kill all its children, so no
proc_mnt will be needed after its death.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Cc: Paul Menage <menage@google.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Pavel Emelyanov 2007-10-18 23:40:11 -07:00 • committed by Linus Torvalds
parent 130f77ecb2
commit 6f4e643353
4 changed files with 39 additions and 0 deletions
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7
kernel/fork.c
View file

@ -50,6 +50,7 @@
#include <linux/taskstats_kern.h>
#include <linux/random.h>
#include <linux/tty.h>
#include <linux/proc_fs.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
@ -1150,6 +1151,12 @@ static struct task_struct *copy_process(unsigned long clone_flags,
pid = alloc_pid(task_active_pid_ns(p));
if (!pid)
goto bad_fork_cleanup_namespaces;
if (clone_flags & CLONE_NEWPID) {
retval = pid_ns_prepare_proc(task_active_pid_ns(p));
if (retval < 0)
goto bad_fork_free_pid;
}
}
p->pid = pid_nr(pid);