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    SubjectRe: [PATCH] do_task_stat: don't use task_pid_nr_ns() lockless
    Eric W. Biederman wrote:
    > Oleg Nesterov <> 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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      Last update: 2007-11-19 10:33    [W:0.020 / U:3.684 seconds]
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