[PATCH 1/1] cgroup_clone: use pid of newly created task for new cgroup
Serge Hallyn
serge at us.ibm.com
Tue Jun 10 13:57:32 PDT 2008
cgroup_clone creates a new cgroup with the pid of the task. This works
correctly for unshare, but for clone cgroup_clone is called from
copy_namespaces inside copy_process, which happens before the new pid
is created. As a result, the new cgroup was created with current's pid.
This patch:
1. Moves the call inside copy_process to after the new pid
is created
2. Passes the struct pid into ns_cgroup_clone (as it is not
yet attached to the task)
3. Passes a name from ns_cgroup_clone() into cgroup_clone()
so as to keep cgroup_clone() itself simpler
4. Uses pid_vnr() to get the process id value, so that the
pid used to name the new cgroup is always the pid as it
would be known to the task which did the cloning or
unsharing. I think that is the most intuitive thing to
do. This way, task t1 does clone(CLONE_NEWPID) to get
t2, which does clone(CLONE_NEWPID) to get t3, then the
cgroup for t3 will be named for the pid by which t2 knows
t3.
This hasn't been tested enough to request inclusion, but I'd like to
get feedback especially from Paul Menage on whether the semantics
make sense.
(Thanks to Dan Smith for finding the main bug)
Signed-off-by: Serge Hallyn <serge at us.ibm.com>
---
include/linux/cgroup.h | 2 +-
include/linux/nsproxy.h | 7 +++++--
kernel/cgroup.c | 16 +++++++---------
kernel/fork.c | 4 ++++
kernel/ns_cgroup.c | 8 ++++++--
kernel/nsproxy.c | 8 +-------
6 files changed, 24 insertions(+), 21 deletions(-)
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 3690c3b..d9b3022 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -349,7 +349,7 @@ static inline struct cgroup* task_cgroup(struct task_struct *task,
return task_subsys_state(task, subsys_id)->cgroup;
}
-int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *ss);
+int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *ss, char *name);
/* A cgroup_iter should be treated as an opaque object */
struct cgroup_iter {
diff --git a/include/linux/nsproxy.h b/include/linux/nsproxy.h
index 0e66b57..c8a768e 100644
--- a/include/linux/nsproxy.h
+++ b/include/linux/nsproxy.h
@@ -82,9 +82,12 @@ static inline void get_nsproxy(struct nsproxy *ns)
}
#ifdef CONFIG_CGROUP_NS
-int ns_cgroup_clone(struct task_struct *tsk);
+int ns_cgroup_clone(struct task_struct *tsk, struct pid *pid);
#else
-static inline int ns_cgroup_clone(struct task_struct *tsk) { return 0; }
+static inline int ns_cgroup_clone(struct task_struct *tsk, struct pid *pid)
+{
+ return 0;
+}
#endif
#endif
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 79fa060..53b54db 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2874,11 +2874,11 @@ void cgroup_exit(struct task_struct *tsk, int run_callbacks)
* subsystem is attached to, and move this task into the new
* child.
*/
-int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys)
+int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys,
+ char *name)
{
struct dentry *dentry;
int ret = 0;
- char nodename[MAX_CGROUP_TYPE_NAMELEN];
struct cgroup *parent, *child;
struct inode *inode;
struct css_set *cg;
@@ -2903,8 +2903,6 @@ int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys)
cg = tsk->cgroups;
parent = task_cgroup(tsk, subsys->subsys_id);
- snprintf(nodename, MAX_CGROUP_TYPE_NAMELEN, "%d", tsk->pid);
-
/* Pin the hierarchy */
atomic_inc(&parent->root->sb->s_active);
@@ -2918,10 +2916,10 @@ int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys)
/* Hold the parent directory mutex across this operation to
* stop anyone else deleting the new cgroup */
mutex_lock(&inode->i_mutex);
- dentry = lookup_one_len(nodename, parent->dentry, strlen(nodename));
+ dentry = lookup_one_len(name, parent->dentry, strlen(name));
if (IS_ERR(dentry)) {
printk(KERN_INFO
- "cgroup: Couldn't allocate dentry for %s: %ld\n", nodename,
+ "cgroup: Couldn't allocate dentry for %s: %ld\n", name,
PTR_ERR(dentry));
ret = PTR_ERR(dentry);
goto out_release;
@@ -2933,14 +2931,14 @@ int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys)
dput(dentry);
if (ret) {
printk(KERN_INFO
- "Failed to create cgroup %s: %d\n", nodename,
+ "Failed to create cgroup %s: %d\n", name,
ret);
goto out_release;
}
if (!child) {
printk(KERN_INFO
- "Couldn't find new cgroup %s\n", nodename);
+ "Couldn't find new cgroup %s\n", name);
ret = -ENOMEM;
goto out_release;
}
@@ -2961,7 +2959,7 @@ int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys)
* point. */
printk(KERN_INFO
"Race in cgroup_clone() - leaking cgroup %s\n",
- nodename);
+ name);
goto again;
}
diff --git a/kernel/fork.c b/kernel/fork.c
index f0e7767..47c0a97 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1125,6 +1125,10 @@ static struct task_struct *copy_process(unsigned long clone_flags,
if (clone_flags & CLONE_THREAD)
p->tgid = current->tgid;
+ if (current->nsproxy != p->nsproxy)
+ if ((retval = ns_cgroup_clone(p, pid)))
+ goto bad_fork_free_pid;
+
p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
/*
* Clear TID on mm_release()?
diff --git a/kernel/ns_cgroup.c b/kernel/ns_cgroup.c
index 48d7ed6..7334f72 100644
--- a/kernel/ns_cgroup.c
+++ b/kernel/ns_cgroup.c
@@ -24,9 +24,13 @@ static inline struct ns_cgroup *cgroup_to_ns(
struct ns_cgroup, css);
}
-int ns_cgroup_clone(struct task_struct *task)
+int ns_cgroup_clone(struct task_struct *task, struct pid *inpid)
{
- return cgroup_clone(task, &ns_subsys);
+ struct pid *pid = (inpid ? inpid : task_pid(task));
+ char name[MAX_CGROUP_TYPE_NAMELEN];
+
+ snprintf(name, MAX_CGROUP_TYPE_NAMELEN, "%d", pid_vnr(pid));
+ return cgroup_clone(task, &ns_subsys, name);
}
/*
diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
index adc7851..5ca106d 100644
--- a/kernel/nsproxy.c
+++ b/kernel/nsproxy.c
@@ -157,12 +157,6 @@ int copy_namespaces(unsigned long flags, struct task_struct *tsk)
goto out;
}
- err = ns_cgroup_clone(tsk);
- if (err) {
- put_nsproxy(new_ns);
- goto out;
- }
-
tsk->nsproxy = new_ns;
out:
@@ -209,7 +203,7 @@ int unshare_nsproxy_namespaces(unsigned long unshare_flags,
goto out;
}
- err = ns_cgroup_clone(current);
+ err = ns_cgroup_clone(current, NULL);
if (err)
put_nsproxy(*new_nsp);
--
1.5.4.3
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