[PATCH 0/3] procfs wrt pid namespace cleanups

[PATCH 0/3] procfs wrt pid namespace cleanups

[Daniel Lezcano]

This patchset is a cleanup and a preparation to unshare the pid
namespace. These prerequisite prepare the next Eric's patchset
to give a file descriptor to a namespace and join an existing
namespace.

The initial authors of this patchset are Eric Biederman and Oleg
Nesterov.

Changelog:

        02/14/11 - daniel.lezcano@free.fr
        * patch 2/3 : fix return ENOMEM and put_pid_ns on error
        * removed buggy patch #4 from the initial patchset

        01/31/11 - daniel.lezcano@free.fr:
        * patch 1/4 : wrapped test in a function
        * patch 2/4 : handle proc_pid_ns_prepare_proc error
        * patch 2/4 : put parent pid_ns on error
        * other patches : refreshed against linux-next

[PATCH 1/3] pid: Remove the child_reaper special case in init/main.c

[Daniel Lezcano]

From: Eric W. Biederman <ebiederm@xmission.com>

It turns out that the existing assignment in copy_process of
the child_reaper can handle the initial assignment of child_reaper
we just need to generalize the test in kernel/fork.c

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@free.fr>
---
 include/linux/pid.h |   11 +++++++++++
 init/main.c         |    9 ---------
 kernel/fork.c       |    2 +-
 3 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/include/linux/pid.h b/include/linux/pid.h
index 49f1c2f..efceda0 100644
--- a/include/linux/pid.h
+++ b/include/linux/pid.h
@@ -141,6 +141,17 @@ static inline struct pid_namespace *ns_of_pid(struct pid *pid)
 }
 
 /*
+ * is_child_reaper returns true if the pid is the init process
+ * of the current namespace. As this one could be checked before
+ * pid_ns->child_reaper is assigned in copy_process, we check
+ * with the pid number.
+ */
+static inline bool is_child_reaper(struct pid *pid)
+{
+	return pid->numbers[pid->level].nr == 1;
+}
+
+/*
  * the helpers to get the pid's id seen from different namespaces
  *
  * pid_nr()    : global id, i.e. the id seen from the init namespace;
diff --git a/init/main.c b/init/main.c
index 33c37c3..793ebfd 100644
--- a/init/main.c
+++ b/init/main.c
@@ -875,15 +875,6 @@ static int __init kernel_init(void * unused)
 	 * init can run on any cpu.
 	 */
 	set_cpus_allowed_ptr(current, cpu_all_mask);
-	/*
-	 * Tell the world that we're going to be the grim
-	 * reaper of innocent orphaned children.
-	 *
-	 * We don't want people to have to make incorrect
-	 * assumptions about where in the task array this
-	 * can be found.
-	 */
-	init_pid_ns.child_reaper = current;
 
 	cad_pid = task_pid(current);
 
diff --git a/kernel/fork.c b/kernel/fork.c
index 25e4291..c9f0784 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1289,7 +1289,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 		tracehook_finish_clone(p, clone_flags, trace);
 
 		if (thread_group_leader(p)) {
-			if (clone_flags & CLONE_NEWPID)
+			if (is_child_reaper(pid))
 				p->nsproxy->pid_ns->child_reaper = p;
 
 			p->signal->leader_pid = pid;
-- 
1.7.1

Re: [PATCH 1/3] pid: Remove the child_reaper special case in init/main.c

[Serge E. Hallyn]

Quoting Daniel Lezcano (daniel.lezcano@free.fr):
> From: Eric W. Biederman <ebiederm@xmission.com>
> 
> It turns out that the existing assignment in copy_process of
> the child_reaper can handle the initial assignment of child_reaper
> we just need to generalize the test in kernel/fork.c
> 
> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
> Signed-off-by: Daniel Lezcano <daniel.lezcano@free.fr>

Acked-by: Serge E. Hallyn <serge@hallyn.com>

> ---
>  include/linux/pid.h |   11 +++++++++++
>  init/main.c         |    9 ---------
>  kernel/fork.c       |    2 +-
>  3 files changed, 12 insertions(+), 10 deletions(-)
> 
> diff --git a/include/linux/pid.h b/include/linux/pid.h
> index 49f1c2f..efceda0 100644
> --- a/include/linux/pid.h
> +++ b/include/linux/pid.h
> @@ -141,6 +141,17 @@ static inline struct pid_namespace *ns_of_pid(struct pid *pid)
>  }
>  
>  /*
> + * is_child_reaper returns true if the pid is the init process
> + * of the current namespace. As this one could be checked before
> + * pid_ns->child_reaper is assigned in copy_process, we check
> + * with the pid number.
> + */
> +static inline bool is_child_reaper(struct pid *pid)
> +{
> +	return pid->numbers[pid->level].nr == 1;
> +}
> +
> +/*
>   * the helpers to get the pid's id seen from different namespaces
>   *
>   * pid_nr()    : global id, i.e. the id seen from the init namespace;
> diff --git a/init/main.c b/init/main.c
> index 33c37c3..793ebfd 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -875,15 +875,6 @@ static int __init kernel_init(void * unused)
>  	 * init can run on any cpu.
>  	 */
>  	set_cpus_allowed_ptr(current, cpu_all_mask);
> -	/*
> -	 * Tell the world that we're going to be the grim
> -	 * reaper of innocent orphaned children.
> -	 *
> -	 * We don't want people to have to make incorrect
> -	 * assumptions about where in the task array this
> -	 * can be found.
> -	 */
> -	init_pid_ns.child_reaper = current;
>  
>  	cad_pid = task_pid(current);
>  
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 25e4291..c9f0784 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -1289,7 +1289,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
>  		tracehook_finish_clone(p, clone_flags, trace);
>  
>  		if (thread_group_leader(p)) {
> -			if (clone_flags & CLONE_NEWPID)
> +			if (is_child_reaper(pid))
>  				p->nsproxy->pid_ns->child_reaper = p;
>  
>  			p->signal->leader_pid = pid;
> -- 
> 1.7.1
> 
> _______________________________________________
> Containers mailing list
> Containers@lists.linux-foundation.org
> https://lists.linux-foundation.org/mailman/listinfo/containers

[PATCH 2/3] pidns: Call pid_ns_prepare_proc from create_pid_namespace

[Daniel Lezcano]

From: Eric W. Biederman <ebiederm@xmission.com>

Reorganize proc_get_sb so it can be called before the struct pid
of the first process is allocated.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@free.fr>
---
 fs/proc/root.c         |   25 +++++++------------------
 kernel/fork.c          |    6 ------
 kernel/pid_namespace.c |   11 +++++++++--
 3 files changed, 16 insertions(+), 26 deletions(-)

diff --git a/fs/proc/root.c b/fs/proc/root.c
index ef9fa8e..e5e2bfa 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -43,17 +43,6 @@ static struct dentry *proc_mount(struct file_system_type *fs_type,
 	struct pid_namespace *ns;
 	struct proc_inode *ei;
 
-	if (proc_mnt) {
-		/* Seed the root directory with a pid so it doesn't need
-		 * to be special in base.c.  I would do this earlier but
-		 * the only task alive when /proc is mounted the first time
-		 * is the init_task and it doesn't have any pids.
-		 */
-		ei = PROC_I(proc_mnt->mnt_sb->s_root->d_inode);
-		if (!ei->pid)
-			ei->pid = find_get_pid(1);
-	}
-
 	if (flags & MS_KERNMOUNT)
 		ns = (struct pid_namespace *)data;
 	else
@@ -71,16 +60,16 @@ static struct dentry *proc_mount(struct file_system_type *fs_type,
 			return ERR_PTR(err);
 		}
 
-		ei = PROC_I(sb->s_root->d_inode);
-		if (!ei->pid) {
-			rcu_read_lock();
-			ei->pid = get_pid(find_pid_ns(1, ns));
-			rcu_read_unlock();
-		}
-
 		sb->s_flags |= MS_ACTIVE;
 	}
 
+	ei = PROC_I(sb->s_root->d_inode);
+	if (!ei->pid) {
+		rcu_read_lock();
+		ei->pid = get_pid(find_pid_ns(1, ns));
+		rcu_read_unlock();
+	}
+
 	return dget(sb->s_root);
 }
 
diff --git a/kernel/fork.c b/kernel/fork.c
index c9f0784..e7a5907 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1180,12 +1180,6 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 		pid = alloc_pid(p->nsproxy->pid_ns);
 		if (!pid)
 			goto bad_fork_cleanup_io;
-
-		if (clone_flags & CLONE_NEWPID) {
-			retval = pid_ns_prepare_proc(p->nsproxy->pid_ns);
-			if (retval < 0)
-				goto bad_fork_free_pid;
-		}
 	}
 
 	p->pid = pid_nr(pid);
diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index a5aff94..e9c9adc 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -14,6 +14,7 @@
 #include <linux/err.h>
 #include <linux/acct.h>
 #include <linux/slab.h>
+#include <linux/proc_fs.h>
 
 #define BITS_PER_PAGE		(PAGE_SIZE*8)
 
@@ -72,7 +73,7 @@ static struct pid_namespace *create_pid_namespace(struct pid_namespace *parent_p
 {
 	struct pid_namespace *ns;
 	unsigned int level = parent_pid_ns->level + 1;
-	int i;
+	int i, err = -ENOMEM;
 
 	ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL);
 	if (ns == NULL)
@@ -96,14 +97,20 @@ static struct pid_namespace *create_pid_namespace(struct pid_namespace *parent_p
 	for (i = 1; i < PIDMAP_ENTRIES; i++)
 		atomic_set(&ns->pidmap[i].nr_free, BITS_PER_PAGE);
 
+	err = pid_ns_prepare_proc(ns);
+	if (err)
+		goto out_put_parent_pid_ns;
+
 	return ns;
 
+out_put_parent_pid_ns:
+	put_pid_ns(parent_pid_ns);
 out_free_map:
 	kfree(ns->pidmap[0].page);
 out_free:
 	kmem_cache_free(pid_ns_cachep, ns);
 out:
-	return ERR_PTR(-ENOMEM);
+	return ERR_PTR(err);
 }
 
 static void destroy_pid_namespace(struct pid_namespace *ns)
-- 
1.7.1

Re: [PATCH 2/3] pidns: Call pid_ns_prepare_proc from create_pid_namespace

[Serge E. Hallyn]

Quoting Daniel Lezcano (daniel.lezcano@free.fr):
> From: Eric W. Biederman <ebiederm@xmission.com>
> 
> Reorganize proc_get_sb so it can be called before the struct pid
> of the first process is allocated.
> 
> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
> Signed-off-by: Daniel Lezcano <daniel.lezcano@free.fr>

Acked-by: Serge E. Hallyn <serge@hallyn.com>

> ---
>  fs/proc/root.c         |   25 +++++++------------------
>  kernel/fork.c          |    6 ------
>  kernel/pid_namespace.c |   11 +++++++++--
>  3 files changed, 16 insertions(+), 26 deletions(-)
> 
> diff --git a/fs/proc/root.c b/fs/proc/root.c
> index ef9fa8e..e5e2bfa 100644
> --- a/fs/proc/root.c
> +++ b/fs/proc/root.c
> @@ -43,17 +43,6 @@ static struct dentry *proc_mount(struct file_system_type *fs_type,
>  	struct pid_namespace *ns;
>  	struct proc_inode *ei;
>  
> -	if (proc_mnt) {
> -		/* Seed the root directory with a pid so it doesn't need
> -		 * to be special in base.c.  I would do this earlier but
> -		 * the only task alive when /proc is mounted the first time
> -		 * is the init_task and it doesn't have any pids.
> -		 */
> -		ei = PROC_I(proc_mnt->mnt_sb->s_root->d_inode);
> -		if (!ei->pid)
> -			ei->pid = find_get_pid(1);
> -	}
> -
>  	if (flags & MS_KERNMOUNT)
>  		ns = (struct pid_namespace *)data;
>  	else
> @@ -71,16 +60,16 @@ static struct dentry *proc_mount(struct file_system_type *fs_type,
>  			return ERR_PTR(err);
>  		}
>  
> -		ei = PROC_I(sb->s_root->d_inode);
> -		if (!ei->pid) {
> -			rcu_read_lock();
> -			ei->pid = get_pid(find_pid_ns(1, ns));
> -			rcu_read_unlock();
> -		}
> -
>  		sb->s_flags |= MS_ACTIVE;
>  	}
>  
> +	ei = PROC_I(sb->s_root->d_inode);
> +	if (!ei->pid) {
> +		rcu_read_lock();
> +		ei->pid = get_pid(find_pid_ns(1, ns));
> +		rcu_read_unlock();
> +	}
> +
>  	return dget(sb->s_root);
>  }
>  
> diff --git a/kernel/fork.c b/kernel/fork.c
> index c9f0784..e7a5907 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -1180,12 +1180,6 @@ static struct task_struct *copy_process(unsigned long clone_flags,
>  		pid = alloc_pid(p->nsproxy->pid_ns);
>  		if (!pid)
>  			goto bad_fork_cleanup_io;
> -
> -		if (clone_flags & CLONE_NEWPID) {
> -			retval = pid_ns_prepare_proc(p->nsproxy->pid_ns);
> -			if (retval < 0)
> -				goto bad_fork_free_pid;
> -		}
>  	}
>  
>  	p->pid = pid_nr(pid);
> diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
> index a5aff94..e9c9adc 100644
> --- a/kernel/pid_namespace.c
> +++ b/kernel/pid_namespace.c
> @@ -14,6 +14,7 @@
>  #include <linux/err.h>
>  #include <linux/acct.h>
>  #include <linux/slab.h>
> +#include <linux/proc_fs.h>
>  
>  #define BITS_PER_PAGE		(PAGE_SIZE*8)
>  
> @@ -72,7 +73,7 @@ static struct pid_namespace *create_pid_namespace(struct pid_namespace *parent_p
>  {
>  	struct pid_namespace *ns;
>  	unsigned int level = parent_pid_ns->level + 1;
> -	int i;
> +	int i, err = -ENOMEM;
>  
>  	ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL);
>  	if (ns == NULL)
> @@ -96,14 +97,20 @@ static struct pid_namespace *create_pid_namespace(struct pid_namespace *parent_p
>  	for (i = 1; i < PIDMAP_ENTRIES; i++)
>  		atomic_set(&ns->pidmap[i].nr_free, BITS_PER_PAGE);
>  
> +	err = pid_ns_prepare_proc(ns);
> +	if (err)
> +		goto out_put_parent_pid_ns;
> +
>  	return ns;
>  
> +out_put_parent_pid_ns:
> +	put_pid_ns(parent_pid_ns);
>  out_free_map:
>  	kfree(ns->pidmap[0].page);
>  out_free:
>  	kmem_cache_free(pid_ns_cachep, ns);
>  out:
> -	return ERR_PTR(-ENOMEM);
> +	return ERR_PTR(err);
>  }
>  
>  static void destroy_pid_namespace(struct pid_namespace *ns)
> -- 
> 1.7.1
> 
> _______________________________________________
> Containers mailing list
> Containers@lists.linux-foundation.org
> https://lists.linux-foundation.org/mailman/listinfo/containers

[PATCH 3/3] procfs: kill the global proc_mnt variable

[Daniel Lezcano]

From: Oleg Nesterov <oleg@redhat.com>

After the previous cleanup in proc_get_sb() the global proc_mnt has
no reasons to exists, kill it.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@free.fr>
---
 fs/proc/inode.c    |    2 --
 fs/proc/internal.h |    1 -
 fs/proc/root.c     |    7 ++++---
 3 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index 176ce4c..ee0f802 100644
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -42,8 +42,6 @@ static void proc_evict_inode(struct inode *inode)
 		sysctl_head_put(PROC_I(inode)->sysctl);
 }
 
-struct vfsmount *proc_mnt;
-
 static struct kmem_cache * proc_inode_cachep;
 
 static struct inode *proc_alloc_inode(struct super_block *sb)
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index 9ad561d..c03e8d3 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -107,7 +107,6 @@ static inline struct proc_dir_entry *pde_get(struct proc_dir_entry *pde)
 }
 void pde_put(struct proc_dir_entry *pde);
 
-extern struct vfsmount *proc_mnt;
 int proc_fill_super(struct super_block *);
 struct inode *proc_get_inode(struct super_block *, struct proc_dir_entry *);
 
diff --git a/fs/proc/root.c b/fs/proc/root.c
index e5e2bfa..a9000e9 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -90,19 +90,20 @@ static struct file_system_type proc_fs_type = {
 
 void __init proc_root_init(void)
 {
+	struct vfsmount *mnt;
 	int err;
 
 	proc_init_inodecache();
 	err = register_filesystem(&proc_fs_type);
 	if (err)
 		return;
-	proc_mnt = kern_mount_data(&proc_fs_type, &init_pid_ns);
-	if (IS_ERR(proc_mnt)) {
+	mnt = kern_mount_data(&proc_fs_type, &init_pid_ns);
+	if (IS_ERR(mnt)) {
 		unregister_filesystem(&proc_fs_type);
 		return;
 	}
 
-	init_pid_ns.proc_mnt = proc_mnt;
+	init_pid_ns.proc_mnt = mnt;
 	proc_symlink("mounts", NULL, "self/mounts");
 
 	proc_net_init();
-- 
1.7.1

Re: [PATCH 3/3] procfs: kill the global proc_mnt variable

[Serge E. Hallyn]

Quoting Daniel Lezcano (daniel.lezcano@free.fr):
> From: Oleg Nesterov <oleg@redhat.com>
> 
> After the previous cleanup in proc_get_sb() the global proc_mnt has
> no reasons to exists, kill it.
> 
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
> Signed-off-by: Daniel Lezcano <daniel.lezcano@free.fr>

Acked-by: Serge E. Hallyn <serge@hallyn.com>

> ---
>  fs/proc/inode.c    |    2 --
>  fs/proc/internal.h |    1 -
>  fs/proc/root.c     |    7 ++++---
>  3 files changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/proc/inode.c b/fs/proc/inode.c
> index 176ce4c..ee0f802 100644
> --- a/fs/proc/inode.c
> +++ b/fs/proc/inode.c
> @@ -42,8 +42,6 @@ static void proc_evict_inode(struct inode *inode)
>  		sysctl_head_put(PROC_I(inode)->sysctl);
>  }
>  
> -struct vfsmount *proc_mnt;
> -
>  static struct kmem_cache * proc_inode_cachep;
>  
>  static struct inode *proc_alloc_inode(struct super_block *sb)
> diff --git a/fs/proc/internal.h b/fs/proc/internal.h
> index 9ad561d..c03e8d3 100644
> --- a/fs/proc/internal.h
> +++ b/fs/proc/internal.h
> @@ -107,7 +107,6 @@ static inline struct proc_dir_entry *pde_get(struct proc_dir_entry *pde)
>  }
>  void pde_put(struct proc_dir_entry *pde);
>  
> -extern struct vfsmount *proc_mnt;
>  int proc_fill_super(struct super_block *);
>  struct inode *proc_get_inode(struct super_block *, struct proc_dir_entry *);
>  
> diff --git a/fs/proc/root.c b/fs/proc/root.c
> index e5e2bfa..a9000e9 100644
> --- a/fs/proc/root.c
> +++ b/fs/proc/root.c
> @@ -90,19 +90,20 @@ static struct file_system_type proc_fs_type = {
>  
>  void __init proc_root_init(void)
>  {
> +	struct vfsmount *mnt;
>  	int err;
>  
>  	proc_init_inodecache();
>  	err = register_filesystem(&proc_fs_type);
>  	if (err)
>  		return;
> -	proc_mnt = kern_mount_data(&proc_fs_type, &init_pid_ns);
> -	if (IS_ERR(proc_mnt)) {
> +	mnt = kern_mount_data(&proc_fs_type, &init_pid_ns);
> +	if (IS_ERR(mnt)) {
>  		unregister_filesystem(&proc_fs_type);
>  		return;
>  	}
>  
> -	init_pid_ns.proc_mnt = proc_mnt;
> +	init_pid_ns.proc_mnt = mnt;
>  	proc_symlink("mounts", NULL, "self/mounts");
>  
>  	proc_net_init();
> -- 
> 1.7.1
> 
> _______________________________________________
> Containers mailing list
> Containers@lists.linux-foundation.org
> https://lists.linux-foundation.org/mailman/listinfo/containers

Re: [PATCH 0/3] procfs wrt pid namespace cleanups

[Oleg Nesterov]

On 02/14, Daniel Lezcano wrote:
>
>         * removed buggy patch #4 from the initial patchset

Hmm. probably it was me who confused you... I am sorry if this is true.

I don't think that patch was buggy.  What I meant, it looks like
the preparation for the next changes
(http://kerneltrap.org/mailarchive/linux-kernel/2010/6/20/4585095)
and those changes are not correct.

In fact, 1/3 looks the same.

Anyway, this series looks correct.

Oleg.