| Message ID | 148440329770.30622.16593902895676160550.stgit@localhost.localdomain (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Sat, Jan 14, 2017 at 05:15:04PM +0300, Kirill Tkhai wrote: > For correct checkpointing/restoring of a task from userspace > it's need to know the task's pid_ns_for_children. Currently, > there is no a sane way to do that (the only possible trick > is to force the task create a new child and to analize the > child's /proc/[pid]/ns/pid link, that is performance-stupid). > > The patch exposes pid_ns_for_children to ns directory > in standard way with the name "pid_for_children": > > ~# ls /proc/5531/ns -l | grep pid > lrwxrwxrwx 1 root root 0 Jan 14 16:38 pid -> pid:[4026531836] > lrwxrwxrwx 1 root root 0 Jan 14 16:38 pid_for_children -> pid:[4026532286] > Cc: linux-api, Michael Kerrisk Acked-by: Andrei Vagin <avagin@virtuozzo.com> > Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com> > --- > fs/proc/namespaces.c | 1 + > include/linux/proc_ns.h | 1 + > kernel/pid_namespace.c | 25 +++++++++++++++++++++++++ > 3 files changed, 27 insertions(+) > > diff --git a/fs/proc/namespaces.c b/fs/proc/namespaces.c > index 766f0c637ad1..3803b24ca220 100644 > --- a/fs/proc/namespaces.c > +++ b/fs/proc/namespaces.c > @@ -23,6 +23,7 @@ static const struct proc_ns_operations *ns_entries[] = { > #endif > #ifdef CONFIG_PID_NS > &pidns_operations, > + &pidns_for_children_operations, > #endif > #ifdef CONFIG_USER_NS > &userns_operations, > diff --git a/include/linux/proc_ns.h b/include/linux/proc_ns.h > index 88dba3b53375..58ab28d81fc2 100644 > --- a/include/linux/proc_ns.h > +++ b/include/linux/proc_ns.h > @@ -27,6 +27,7 @@ extern const struct proc_ns_operations netns_operations; > extern const struct proc_ns_operations utsns_operations; > extern const struct proc_ns_operations ipcns_operations; > extern const struct proc_ns_operations pidns_operations; > +extern const struct proc_ns_operations pidns_for_children_operations; > extern const struct proc_ns_operations userns_operations; > extern const struct proc_ns_operations mntns_operations; > extern const struct proc_ns_operations cgroupns_operations; > diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c > index df9e8e9e0be7..cbe950d4a11e 100644 > --- a/kernel/pid_namespace.c > +++ b/kernel/pid_namespace.c > @@ -369,6 +369,20 @@ static struct ns_common *pidns_get(struct task_struct *task) > return ns ? &ns->ns : NULL; > } > > +static struct ns_common *pidns_for_children_get(struct task_struct *task) > +{ > + struct pid_namespace *ns = NULL; > + > + task_lock(task); > + if (task->nsproxy) { > + ns = task->nsproxy->pid_ns_for_children; > + get_pid_ns(ns); > + } > + task_unlock(task); > + > + return ns ? &ns->ns : NULL; > +} > + > static void pidns_put(struct ns_common *ns) > { > put_pid_ns(to_pid_ns(ns)); > @@ -438,6 +452,17 @@ const struct proc_ns_operations pidns_operations = { > .get_parent = pidns_get_parent, > }; > > +const struct proc_ns_operations pidns_for_children_operations = { > + .name = "pid_for_children", > + .real_ns_name = "pid", > + .type = CLONE_NEWPID, > + .get = pidns_for_children_get, > + .put = pidns_put, > + .install = pidns_install, > + .owner = pidns_owner, > + .get_parent = pidns_get_parent, > +}; > + > static __init int pid_namespaces_init(void) > { > pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC); > -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 14 January 2017 at 15:15, Kirill Tkhai <ktkhai@virtuozzo.com> wrote: > For correct checkpointing/restoring of a task from userspace > it's need to know the task's pid_ns_for_children. Currently, > there is no a sane way to do that (the only possible trick > is to force the task create a new child and to analize the > child's /proc/[pid]/ns/pid link, that is performance-stupid). > > The patch exposes pid_ns_for_children to ns directory > in standard way with the name "pid_for_children": > > ~# ls /proc/5531/ns -l | grep pid > lrwxrwxrwx 1 root root 0 Jan 14 16:38 pid -> pid:[4026531836] > lrwxrwxrwx 1 root root 0 Jan 14 16:38 pid_for_children -> pid:[4026532286] > > Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com> What's happening if a process, after unsharing CLONE_NEWPID, does not fork but instead let another process open the new "pid_for_children" and then setns()+fork()? Is that other process allowed to create the "pid 1" in the new pid namespaces? Is that also allowed if the other process lives in a sibling pid namespace? If so, that would break what pid_namespaces(7) says: "the parental relationship between processes mirrors the parental relationship between PID namespaces: the parent of a process is either in the same namespace or resides in the immediate parent PID namespace." -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 24.01.2017 00:49, Alban Crequy wrote: > On 14 January 2017 at 15:15, Kirill Tkhai <ktkhai@virtuozzo.com> wrote: >> For correct checkpointing/restoring of a task from userspace >> it's need to know the task's pid_ns_for_children. Currently, >> there is no a sane way to do that (the only possible trick >> is to force the task create a new child and to analize the >> child's /proc/[pid]/ns/pid link, that is performance-stupid). >> >> The patch exposes pid_ns_for_children to ns directory >> in standard way with the name "pid_for_children": >> >> ~# ls /proc/5531/ns -l | grep pid >> lrwxrwxrwx 1 root root 0 Jan 14 16:38 pid -> pid:[4026531836] >> lrwxrwxrwx 1 root root 0 Jan 14 16:38 pid_for_children -> pid:[4026532286] >> >> Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com> > > What's happening if a process, after unsharing CLONE_NEWPID, does not > fork but instead let another process open the new "pid_for_children" > and then setns()+fork()? Is that other process allowed to create the > "pid 1" in the new pid namespaces? Is that also allowed if the other > process lives in a sibling pid namespace? If so, that would break what > pid_namespaces(7) says: > > "the parental relationship between processes mirrors the parental > relationship between PID namespaces: the parent of a process is > either in the same namespace or resides in the immediate parent > PID namespace." > You can setns() on a pid_ns only if your active pid_ns is a (grand)parent for the target pid_ns. So, the situation you described is not possible. See pidns_install() for the details. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
ping On 14.01.2017 17:15, Kirill Tkhai wrote: > For correct checkpointing/restoring of a task from userspace > it's need to know the task's pid_ns_for_children. Currently, > there is no a sane way to do that (the only possible trick > is to force the task create a new child and to analize the > child's /proc/[pid]/ns/pid link, that is performance-stupid). > > The patch exposes pid_ns_for_children to ns directory > in standard way with the name "pid_for_children": > > ~# ls /proc/5531/ns -l | grep pid > lrwxrwxrwx 1 root root 0 Jan 14 16:38 pid -> pid:[4026531836] > lrwxrwxrwx 1 root root 0 Jan 14 16:38 pid_for_children -> pid:[4026532286] > > Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com> > --- > fs/proc/namespaces.c | 1 + > include/linux/proc_ns.h | 1 + > kernel/pid_namespace.c | 25 +++++++++++++++++++++++++ > 3 files changed, 27 insertions(+) > > diff --git a/fs/proc/namespaces.c b/fs/proc/namespaces.c > index 766f0c637ad1..3803b24ca220 100644 > --- a/fs/proc/namespaces.c > +++ b/fs/proc/namespaces.c > @@ -23,6 +23,7 @@ static const struct proc_ns_operations *ns_entries[] = { > #endif > #ifdef CONFIG_PID_NS > &pidns_operations, > + &pidns_for_children_operations, > #endif > #ifdef CONFIG_USER_NS > &userns_operations, > diff --git a/include/linux/proc_ns.h b/include/linux/proc_ns.h > index 88dba3b53375..58ab28d81fc2 100644 > --- a/include/linux/proc_ns.h > +++ b/include/linux/proc_ns.h > @@ -27,6 +27,7 @@ extern const struct proc_ns_operations netns_operations; > extern const struct proc_ns_operations utsns_operations; > extern const struct proc_ns_operations ipcns_operations; > extern const struct proc_ns_operations pidns_operations; > +extern const struct proc_ns_operations pidns_for_children_operations; > extern const struct proc_ns_operations userns_operations; > extern const struct proc_ns_operations mntns_operations; > extern const struct proc_ns_operations cgroupns_operations; > diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c > index df9e8e9e0be7..cbe950d4a11e 100644 > --- a/kernel/pid_namespace.c > +++ b/kernel/pid_namespace.c > @@ -369,6 +369,20 @@ static struct ns_common *pidns_get(struct task_struct *task) > return ns ? &ns->ns : NULL; > } > > +static struct ns_common *pidns_for_children_get(struct task_struct *task) > +{ > + struct pid_namespace *ns = NULL; > + > + task_lock(task); > + if (task->nsproxy) { > + ns = task->nsproxy->pid_ns_for_children; > + get_pid_ns(ns); > + } > + task_unlock(task); > + > + return ns ? &ns->ns : NULL; > +} > + > static void pidns_put(struct ns_common *ns) > { > put_pid_ns(to_pid_ns(ns)); > @@ -438,6 +452,17 @@ const struct proc_ns_operations pidns_operations = { > .get_parent = pidns_get_parent, > }; > > +const struct proc_ns_operations pidns_for_children_operations = { > + .name = "pid_for_children", > + .real_ns_name = "pid", > + .type = CLONE_NEWPID, > + .get = pidns_for_children_get, > + .put = pidns_put, > + .install = pidns_install, > + .owner = pidns_owner, > + .get_parent = pidns_get_parent, > +}; > + > static __init int pid_namespaces_init(void) > { > pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC); > -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/fs/proc/namespaces.c b/fs/proc/namespaces.c index 766f0c637ad1..3803b24ca220 100644 --- a/fs/proc/namespaces.c +++ b/fs/proc/namespaces.c @@ -23,6 +23,7 @@ static const struct proc_ns_operations *ns_entries[] = { #endif #ifdef CONFIG_PID_NS &pidns_operations, + &pidns_for_children_operations, #endif #ifdef CONFIG_USER_NS &userns_operations, diff --git a/include/linux/proc_ns.h b/include/linux/proc_ns.h index 88dba3b53375..58ab28d81fc2 100644 --- a/include/linux/proc_ns.h +++ b/include/linux/proc_ns.h @@ -27,6 +27,7 @@ extern const struct proc_ns_operations netns_operations; extern const struct proc_ns_operations utsns_operations; extern const struct proc_ns_operations ipcns_operations; extern const struct proc_ns_operations pidns_operations; +extern const struct proc_ns_operations pidns_for_children_operations; extern const struct proc_ns_operations userns_operations; extern const struct proc_ns_operations mntns_operations; extern const struct proc_ns_operations cgroupns_operations; diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c index df9e8e9e0be7..cbe950d4a11e 100644 --- a/kernel/pid_namespace.c +++ b/kernel/pid_namespace.c @@ -369,6 +369,20 @@ static struct ns_common *pidns_get(struct task_struct *task) return ns ? &ns->ns : NULL; } +static struct ns_common *pidns_for_children_get(struct task_struct *task) +{ + struct pid_namespace *ns = NULL; + + task_lock(task); + if (task->nsproxy) { + ns = task->nsproxy->pid_ns_for_children; + get_pid_ns(ns); + } + task_unlock(task); + + return ns ? &ns->ns : NULL; +} + static void pidns_put(struct ns_common *ns) { put_pid_ns(to_pid_ns(ns)); @@ -438,6 +452,17 @@ const struct proc_ns_operations pidns_operations = { .get_parent = pidns_get_parent, }; +const struct proc_ns_operations pidns_for_children_operations = { + .name = "pid_for_children", + .real_ns_name = "pid", + .type = CLONE_NEWPID, + .get = pidns_for_children_get, + .put = pidns_put, + .install = pidns_install, + .owner = pidns_owner, + .get_parent = pidns_get_parent, +}; + static __init int pid_namespaces_init(void) { pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);
For correct checkpointing/restoring of a task from userspace it's need to know the task's pid_ns_for_children. Currently, there is no a sane way to do that (the only possible trick is to force the task create a new child and to analize the child's /proc/[pid]/ns/pid link, that is performance-stupid). The patch exposes pid_ns_for_children to ns directory in standard way with the name "pid_for_children": ~# ls /proc/5531/ns -l | grep pid lrwxrwxrwx 1 root root 0 Jan 14 16:38 pid -> pid:[4026531836] lrwxrwxrwx 1 root root 0 Jan 14 16:38 pid_for_children -> pid:[4026532286] Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com> --- fs/proc/namespaces.c | 1 + include/linux/proc_ns.h | 1 + kernel/pid_namespace.c | 25 +++++++++++++++++++++++++ 3 files changed, 27 insertions(+) -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html