| Message ID | 149371848646.24418.16693733830230366252.stgit@localhost.localdomain (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Eric, could you give comments about this? On 02.05.2017 12:48, Kirill Tkhai wrote: > On implementing of nested pid namespaces support in CRIU > (checkpoint-restore in userspace tool) we run into > the situation, that it's impossible to create a task with > specific NSpid effectively. After commit 49f4d8b93ccf > "pidns: Capture the user namespace and filter ns_last_pid" > it is impossible to set ns_last_pid on any pid namespace, > except task's active pid_ns (before the commit it was possible > to write to pid_ns_for_children). Thus, if a restored task > in a container has more than one pid_ns levels, the restorer > code must have a task helper for every pid namespace > of the task's pid_ns hierarhy. > > This is a big problem, because of communication with > a helper for every pid_ns in the hierarchy is not cheap. > It's not performance-good as it implies many helpers wakeups > to create a single task (independently, how you communicate > with the helpers). This patch tries to decide the problem. > > It introduces a new pid_ns ioctl(NS_SET_LAST_PID_VEC), > which allows to write a vector of last pids on pid_ns hierarchy. > The vector is passed as array of pids in struct ns_ioc_pid_vec, > written in reverse order. The first number corresponds to > the opened namespace ns_last_pid, the second is to its parent, etc. > So, if you have the pid namespaces hierarchy like: > > pid_ns1 (grand father) > | > v > pid_ns2 (father) > | > v > pid_ns3 (child) > > and the pid_ns3 is open, then the corresponding vector will be > {last_ns_pid3, last_ns_pid2, last_ns_pid1}. This vector may be > short and it may contain less levels. For example, > {last_ns_pid3, last_ns_pid2} or even {last_ns_pid3}, in dependence > of which levels you want to populate. > > v5: Move pid_max up for !CONFIG_CHECKPOINT_RESTORE builds > (found by kbuild test robot). > > v4: Declare struct ns_ioc_pid_vec directly instead of include uapi file. > Make the interface independent of CONFIG_CHECKPOINT_RESTORE. > Include linux/types.h in nsfs.h for pid_t. > Get all vectors at once. > Make checks atomical. > > v3: Use __u32 in uapi instead of unsigned int. > > v2: Kill pid_ns->child_reaper check as it's impossible to have > such a pid namespace file open. > Use generic namespaces ioctl() number. > Pass pids as array, not as a string. > > Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com> > --- > fs/nsfs.c | 5 +++++ > include/linux/pid_namespace.h | 9 ++++++++- > include/uapi/linux/nsfs.h | 8 ++++++++ > kernel/pid_namespace.c | 38 +++++++++++++++++++++++++++++++++++++- > 4 files changed, 58 insertions(+), 2 deletions(-) > > diff --git a/fs/nsfs.c b/fs/nsfs.c > index 323f492e0822..f669a1552003 100644 > --- a/fs/nsfs.c > +++ b/fs/nsfs.c > @@ -6,6 +6,7 @@ > #include <linux/ktime.h> > #include <linux/seq_file.h> > #include <linux/user_namespace.h> > +#include <linux/pid_namespace.h> > #include <linux/nsfs.h> > #include <linux/uaccess.h> > > @@ -186,6 +187,10 @@ static long ns_ioctl(struct file *filp, unsigned int ioctl, > argp = (uid_t __user *) arg; > uid = from_kuid_munged(current_user_ns(), user_ns->owner); > return put_user(uid, argp); > + case NS_SET_LAST_PID_VEC: > + if (ns->ops->type != CLONE_NEWPID) > + return -EINVAL; > + return pidns_set_last_pid_vec(ns, (void *)arg); > default: > return -ENOTTY; > } > diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h > index c2a989dee876..661fad08bf8c 100644 > --- a/include/linux/pid_namespace.h > +++ b/include/linux/pid_namespace.h > @@ -54,6 +54,7 @@ struct pid_namespace { > struct ns_common ns; > }; > > +struct ns_ioc_pid_vec; > extern struct pid_namespace init_pid_ns; > > #define PIDNS_HASH_ADDING (1U << 31) > @@ -71,7 +72,8 @@ extern struct pid_namespace *copy_pid_ns(unsigned long flags, > extern void zap_pid_ns_processes(struct pid_namespace *pid_ns); > extern int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd); > extern void put_pid_ns(struct pid_namespace *ns); > - > +extern long pidns_set_last_pid_vec(struct ns_common *ns, > + struct ns_ioc_pid_vec __user *vec); > #else /* !CONFIG_PID_NS */ > #include <linux/err.h> > > @@ -101,6 +103,11 @@ static inline int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd) > { > return 0; > } > +static inline long pidns_set_last_pid_vec(struct ns_common *ns, > + struct ns_ioc_pid_vec __user *vec) > +{ > + return -ENOTTY; > +} > #endif /* CONFIG_PID_NS */ > > extern struct pid_namespace *task_active_pid_ns(struct task_struct *tsk); > diff --git a/include/uapi/linux/nsfs.h b/include/uapi/linux/nsfs.h > index 1a3ca79f466b..9d320276eafe 100644 > --- a/include/uapi/linux/nsfs.h > +++ b/include/uapi/linux/nsfs.h > @@ -2,6 +2,7 @@ > #define __LINUX_NSFS_H > > #include <linux/ioctl.h> > +#include <linux/types.h> > > #define NSIO 0xb7 > > @@ -14,5 +15,12 @@ > #define NS_GET_NSTYPE _IO(NSIO, 0x3) > /* Get owner UID (in the caller's user namespace) for a user namespace */ > #define NS_GET_OWNER_UID _IO(NSIO, 0x4) > +/* Set a vector of ns_last_pid for a pid namespace stack */ > +#define NS_SET_LAST_PID_VEC _IO(NSIO, 0x5) > + > +struct ns_ioc_pid_vec { > + __u32 nr; > + pid_t pid[0]; > +}; > > #endif /* __LINUX_NSFS_H */ > diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c > index de461aa0bf9a..d675b4d22dfe 100644 > --- a/kernel/pid_namespace.c > +++ b/kernel/pid_namespace.c > @@ -21,6 +21,7 @@ > #include <linux/export.h> > #include <linux/sched/task.h> > #include <linux/sched/signal.h> > +#include <uapi/linux/nsfs.h> > > struct pid_cache { > int nr_ids; > @@ -32,6 +33,7 @@ struct pid_cache { > static LIST_HEAD(pid_caches_lh); > static DEFINE_MUTEX(pid_caches_mutex); > static struct kmem_cache *pid_ns_cachep; > +extern int pid_max; > > /* > * creates the kmem cache to allocate pids from. > @@ -311,7 +313,6 @@ static int pid_ns_ctl_handler(struct ctl_table *table, int write, > return proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos); > } > > -extern int pid_max; > static int zero = 0; > static struct ctl_table pid_ns_ctl_table[] = { > { > @@ -428,6 +429,41 @@ static struct ns_common *pidns_get_parent(struct ns_common *ns) > return &get_pid_ns(pid_ns)->ns; > } > > +long pidns_set_last_pid_vec(struct ns_common *ns, > + struct ns_ioc_pid_vec __user *vec) > +{ > + struct pid_namespace *pid_ns = to_pid_ns(ns), *top; > + pid_t pid[MAX_PID_NS_LEVEL]; > + u32 i, nr; > + > + BUILD_BUG_ON(sizeof(pid_t) * MAX_PID_NS_LEVEL > 128); > + if (get_user(nr, &vec->nr)) > + return -EFAULT; > + if (nr > MAX_PID_NS_LEVEL || nr < 1) > + return -EINVAL; > + if (copy_from_user(pid, &vec->pid[0], nr * sizeof(pid_t)) != 0) > + return -EFAULT; > + > + top = pid_ns; > + for (i = 0; i < nr-1; i++) { > + top = top->parent; > + if (!top || pid[i] < 0 || pid[i] > pid_max) > + return -EINVAL; > + } > + if (!ns_capable(top->user_ns, CAP_SYS_ADMIN)) > + return -EPERM; > + if (pid[nr-1] < 0 || pid[nr-1] > pid_max) > + return -EINVAL; > + > + for (i = 0; i < nr; i++) { > + /* Write directly: see the comment in pid_ns_ctl_handler() */ > + pid_ns->last_pid = pid[i]; > + pid_ns = pid_ns->parent; > + } > + > + return 0; > +} > + > static struct user_namespace *pidns_owner(struct ns_common *ns) > { > return to_pid_ns(ns)->user_ns; >
diff --git a/fs/nsfs.c b/fs/nsfs.c index 323f492e0822..f669a1552003 100644 --- a/fs/nsfs.c +++ b/fs/nsfs.c @@ -6,6 +6,7 @@ #include <linux/ktime.h> #include <linux/seq_file.h> #include <linux/user_namespace.h> +#include <linux/pid_namespace.h> #include <linux/nsfs.h> #include <linux/uaccess.h> @@ -186,6 +187,10 @@ static long ns_ioctl(struct file *filp, unsigned int ioctl, argp = (uid_t __user *) arg; uid = from_kuid_munged(current_user_ns(), user_ns->owner); return put_user(uid, argp); + case NS_SET_LAST_PID_VEC: + if (ns->ops->type != CLONE_NEWPID) + return -EINVAL; + return pidns_set_last_pid_vec(ns, (void *)arg); default: return -ENOTTY; } diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h index c2a989dee876..661fad08bf8c 100644 --- a/include/linux/pid_namespace.h +++ b/include/linux/pid_namespace.h @@ -54,6 +54,7 @@ struct pid_namespace { struct ns_common ns; }; +struct ns_ioc_pid_vec; extern struct pid_namespace init_pid_ns; #define PIDNS_HASH_ADDING (1U << 31) @@ -71,7 +72,8 @@ extern struct pid_namespace *copy_pid_ns(unsigned long flags, extern void zap_pid_ns_processes(struct pid_namespace *pid_ns); extern int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd); extern void put_pid_ns(struct pid_namespace *ns); - +extern long pidns_set_last_pid_vec(struct ns_common *ns, + struct ns_ioc_pid_vec __user *vec); #else /* !CONFIG_PID_NS */ #include <linux/err.h> @@ -101,6 +103,11 @@ static inline int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd) { return 0; } +static inline long pidns_set_last_pid_vec(struct ns_common *ns, + struct ns_ioc_pid_vec __user *vec) +{ + return -ENOTTY; +} #endif /* CONFIG_PID_NS */ extern struct pid_namespace *task_active_pid_ns(struct task_struct *tsk); diff --git a/include/uapi/linux/nsfs.h b/include/uapi/linux/nsfs.h index 1a3ca79f466b..9d320276eafe 100644 --- a/include/uapi/linux/nsfs.h +++ b/include/uapi/linux/nsfs.h @@ -2,6 +2,7 @@ #define __LINUX_NSFS_H #include <linux/ioctl.h> +#include <linux/types.h> #define NSIO 0xb7 @@ -14,5 +15,12 @@ #define NS_GET_NSTYPE _IO(NSIO, 0x3) /* Get owner UID (in the caller's user namespace) for a user namespace */ #define NS_GET_OWNER_UID _IO(NSIO, 0x4) +/* Set a vector of ns_last_pid for a pid namespace stack */ +#define NS_SET_LAST_PID_VEC _IO(NSIO, 0x5) + +struct ns_ioc_pid_vec { + __u32 nr; + pid_t pid[0]; +}; #endif /* __LINUX_NSFS_H */ diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c index de461aa0bf9a..d675b4d22dfe 100644 --- a/kernel/pid_namespace.c +++ b/kernel/pid_namespace.c @@ -21,6 +21,7 @@ #include <linux/export.h> #include <linux/sched/task.h> #include <linux/sched/signal.h> +#include <uapi/linux/nsfs.h> struct pid_cache { int nr_ids; @@ -32,6 +33,7 @@ struct pid_cache { static LIST_HEAD(pid_caches_lh); static DEFINE_MUTEX(pid_caches_mutex); static struct kmem_cache *pid_ns_cachep; +extern int pid_max; /* * creates the kmem cache to allocate pids from. @@ -311,7 +313,6 @@ static int pid_ns_ctl_handler(struct ctl_table *table, int write, return proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos); } -extern int pid_max; static int zero = 0; static struct ctl_table pid_ns_ctl_table[] = { { @@ -428,6 +429,41 @@ static struct ns_common *pidns_get_parent(struct ns_common *ns) return &get_pid_ns(pid_ns)->ns; } +long pidns_set_last_pid_vec(struct ns_common *ns, + struct ns_ioc_pid_vec __user *vec) +{ + struct pid_namespace *pid_ns = to_pid_ns(ns), *top; + pid_t pid[MAX_PID_NS_LEVEL]; + u32 i, nr; + + BUILD_BUG_ON(sizeof(pid_t) * MAX_PID_NS_LEVEL > 128); + if (get_user(nr, &vec->nr)) + return -EFAULT; + if (nr > MAX_PID_NS_LEVEL || nr < 1) + return -EINVAL; + if (copy_from_user(pid, &vec->pid[0], nr * sizeof(pid_t)) != 0) + return -EFAULT; + + top = pid_ns; + for (i = 0; i < nr-1; i++) { + top = top->parent; + if (!top || pid[i] < 0 || pid[i] > pid_max) + return -EINVAL; + } + if (!ns_capable(top->user_ns, CAP_SYS_ADMIN)) + return -EPERM; + if (pid[nr-1] < 0 || pid[nr-1] > pid_max) + return -EINVAL; + + for (i = 0; i < nr; i++) { + /* Write directly: see the comment in pid_ns_ctl_handler() */ + pid_ns->last_pid = pid[i]; + pid_ns = pid_ns->parent; + } + + return 0; +} + static struct user_namespace *pidns_owner(struct ns_common *ns) { return to_pid_ns(ns)->user_ns;
On implementing of nested pid namespaces support in CRIU (checkpoint-restore in userspace tool) we run into the situation, that it's impossible to create a task with specific NSpid effectively. After commit 49f4d8b93ccf "pidns: Capture the user namespace and filter ns_last_pid" it is impossible to set ns_last_pid on any pid namespace, except task's active pid_ns (before the commit it was possible to write to pid_ns_for_children). Thus, if a restored task in a container has more than one pid_ns levels, the restorer code must have a task helper for every pid namespace of the task's pid_ns hierarhy. This is a big problem, because of communication with a helper for every pid_ns in the hierarchy is not cheap. It's not performance-good as it implies many helpers wakeups to create a single task (independently, how you communicate with the helpers). This patch tries to decide the problem. It introduces a new pid_ns ioctl(NS_SET_LAST_PID_VEC), which allows to write a vector of last pids on pid_ns hierarchy. The vector is passed as array of pids in struct ns_ioc_pid_vec, written in reverse order. The first number corresponds to the opened namespace ns_last_pid, the second is to its parent, etc. So, if you have the pid namespaces hierarchy like: pid_ns1 (grand father) | v pid_ns2 (father) | v pid_ns3 (child) and the pid_ns3 is open, then the corresponding vector will be {last_ns_pid3, last_ns_pid2, last_ns_pid1}. This vector may be short and it may contain less levels. For example, {last_ns_pid3, last_ns_pid2} or even {last_ns_pid3}, in dependence of which levels you want to populate. v5: Move pid_max up for !CONFIG_CHECKPOINT_RESTORE builds (found by kbuild test robot). v4: Declare struct ns_ioc_pid_vec directly instead of include uapi file. Make the interface independent of CONFIG_CHECKPOINT_RESTORE. Include linux/types.h in nsfs.h for pid_t. Get all vectors at once. Make checks atomical. v3: Use __u32 in uapi instead of unsigned int. v2: Kill pid_ns->child_reaper check as it's impossible to have such a pid namespace file open. Use generic namespaces ioctl() number. Pass pids as array, not as a string. Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com> --- fs/nsfs.c | 5 +++++ include/linux/pid_namespace.h | 9 ++++++++- include/uapi/linux/nsfs.h | 8 ++++++++ kernel/pid_namespace.c | 38 +++++++++++++++++++++++++++++++++++++- 4 files changed, 58 insertions(+), 2 deletions(-)