Messages in this thread Patch in this message | | | Date | Tue, 16 Dec 2008 16:02:57 -0800 | From | Sukadev Bhattiprolu <> | Subject | [PATCH 1/2][v2] pid: Implement ns_of_pid |
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Resending patch with correct "From", "Signed-off-by" and a note in function header of ns_of_pid().
--- From: Eric Biederman <ebiederm@xmission.com> Subject: [PATCH] pid: Implement ns_of_pid
A current problem with the pid namespace is that it is easy to do pid related work after exit_task_namespaces which drops the nsproxy pointer.
However if we are doing pid namespace related work we are always operating on some struct pid which retains the pid_namespace pointer of the pid namespace it was allocated in.
So provide ns_of_pid which allows us to find the pid namespace a pid was allocated in.
Using this we have the needed infrastructure to do pid namespace related work at anytime we have a struct pid, removing the chance of accidentally having a NULL pointer dereference when accessing current->nsproxy.
Changelog[v2]: - Add a note in function header of ns_of_pid() re: NULL pid.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com> --- include/linux/pid.h | 18 ++++++++++++++++++ 1 files changed, 18 insertions(+), 0 deletions(-)
diff --git a/include/linux/pid.h b/include/linux/pid.h index d7e98ff..da6f174 100644 --- a/include/linux/pid.h +++ b/include/linux/pid.h @@ -122,6 +122,24 @@ int next_pidmap(struct pid_namespace *pid_ns, int last); extern struct pid *alloc_pid(struct pid_namespace *ns); extern void free_pid(struct pid *pid); +/* + * ns_of_pid() returns the pid namespace in which the specified pid was + * allocated. + * + * NOTE: + * ns_of_pid() is expected to be called for a process (task) that has + * an attached 'struct pid' (see attach_pid(), detach_pid()) i.e @pid + * is expected to be non-NULL. If @pid is NULL, caller should handle + * the resulting NULL pid-ns. + */ +static inline struct pid_namespace *ns_of_pid(struct pid *pid) +{ + struct pid_namespace *ns = NULL; + if (pid) + ns = pid->numbers[pid->level].ns; + return ns; +} + /* * the helpers to get the pid's id seen from different namespaces * -- 1.5.2.5
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