Messages in this thread | | | Date | Mon, 19 Nov 2007 12:30:15 +0300 | From | Pavel Emelyanov <> | Subject | Re: [PATCH] do_task_stat: don't use task_pid_nr_ns() lockless |
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Eric W. Biederman wrote: > Oleg Nesterov <oleg@tv-sign.ru> writes: > >> Without rcu/tasklist/siglock lock task_pid_nr_ns() may read the freed memory, >> move the callsite under ->siglock. >> >> Sadly, we can report pid == 0 if the task was detached. > > We only get detached in release_task so it is a pretty small window > where we can return pid == 0. Usually get_task_pid will fail first > and we will return -ESRCH. Still the distance from open to > > There is another bug in here as well. current->nsproxy->pid_ns is wrong. > What we want is: ns = dentry->d_sb->s_fs_info;
Actually I thought about this recently - if we produce the list of tasks based on the sb's namespace, then we should fill the tasks' files according to the sb's namespace as well, not according to the current namespace.
> Otherwise we will have file descriptor passing races and the like.
Can you elaborate?
> We could also do: proc_pid(inode) to get the pid, which is a little > more race free, and will prevent us from returning pid == 0. > > In either event it looks like we need to implement some proper > file operations for these proc files, maybe even going to seq file > status. > > Eric >
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