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-rw-r--r--fs/proc/base.c27
-rw-r--r--include/linux/nsproxy.h43
-rw-r--r--kernel/exit.c7
-rw-r--r--kernel/fork.c11
-rw-r--r--kernel/nsproxy.c40
-rw-r--r--net/core/rtnetlink.c8
6 files changed, 91 insertions, 45 deletions
diff --git a/fs/proc/base.c b/fs/proc/base.c
index fbff900fd5a..6afca09a653 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -350,18 +350,21 @@ struct proc_mounts {
static int mounts_open(struct inode *inode, struct file *file)
{
struct task_struct *task = get_proc_task(inode);
+ struct nsproxy *nsp;
struct mnt_namespace *ns = NULL;
struct proc_mounts *p;
int ret = -EINVAL;
if (task) {
- task_lock(task);
- if (task->nsproxy) {
- ns = task->nsproxy->mnt_ns;
+ rcu_read_lock();
+ nsp = task_nsproxy(task);
+ if (nsp) {
+ ns = nsp->mnt_ns;
if (ns)
get_mnt_ns(ns);
}
- task_unlock(task);
+ rcu_read_unlock();
+
put_task_struct(task);
}
@@ -424,16 +427,20 @@ static int mountstats_open(struct inode *inode, struct file *file)
if (!ret) {
struct seq_file *m = file->private_data;
+ struct nsproxy *nsp;
struct mnt_namespace *mnt_ns = NULL;
struct task_struct *task = get_proc_task(inode);
if (task) {
- task_lock(task);
- if (task->nsproxy)
- mnt_ns = task->nsproxy->mnt_ns;
- if (mnt_ns)
- get_mnt_ns(mnt_ns);
- task_unlock(task);
+ rcu_read_lock();
+ nsp = task_nsproxy(task);
+ if (nsp) {
+ mnt_ns = nsp->mnt_ns;
+ if (mnt_ns)
+ get_mnt_ns(mnt_ns);
+ }
+ rcu_read_unlock();
+
put_task_struct(task);
}
diff --git a/include/linux/nsproxy.h b/include/linux/nsproxy.h
index f1eca68751a..0e66b57631f 100644
--- a/include/linux/nsproxy.h
+++ b/include/linux/nsproxy.h
@@ -32,8 +32,39 @@ struct nsproxy {
};
extern struct nsproxy init_nsproxy;
+/*
+ * the namespaces access rules are:
+ *
+ * 1. only current task is allowed to change tsk->nsproxy pointer or
+ * any pointer on the nsproxy itself
+ *
+ * 2. when accessing (i.e. reading) current task's namespaces - no
+ * precautions should be taken - just dereference the pointers
+ *
+ * 3. the access to other task namespaces is performed like this
+ * rcu_read_lock();
+ * nsproxy = task_nsproxy(tsk);
+ * if (nsproxy != NULL) {
+ * / *
+ * * work with the namespaces here
+ * * e.g. get the reference on one of them
+ * * /
+ * } / *
+ * * NULL task_nsproxy() means that this task is
+ * * almost dead (zombie)
+ * * /
+ * rcu_read_unlock();
+ *
+ */
+
+static inline struct nsproxy *task_nsproxy(struct task_struct *tsk)
+{
+ return rcu_dereference(tsk->nsproxy);
+}
+
int copy_namespaces(unsigned long flags, struct task_struct *tsk);
-void get_task_namespaces(struct task_struct *tsk);
+void exit_task_namespaces(struct task_struct *tsk);
+void switch_task_namespaces(struct task_struct *tsk, struct nsproxy *new);
void free_nsproxy(struct nsproxy *ns);
int unshare_nsproxy_namespaces(unsigned long, struct nsproxy **,
struct fs_struct *);
@@ -45,15 +76,9 @@ static inline void put_nsproxy(struct nsproxy *ns)
}
}
-static inline void exit_task_namespaces(struct task_struct *p)
+static inline void get_nsproxy(struct nsproxy *ns)
{
- struct nsproxy *ns = p->nsproxy;
- if (ns) {
- task_lock(p);
- p->nsproxy = NULL;
- task_unlock(p);
- put_nsproxy(ns);
- }
+ atomic_inc(&ns->count);
}
#ifdef CONFIG_CGROUP_NS
diff --git a/kernel/exit.c b/kernel/exit.c
index d22aefabb12..db9764186d5 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -400,9 +400,10 @@ void daemonize(const char *name, ...)
current->fs = fs;
atomic_inc(&fs->count);
- exit_task_namespaces(current);
- current->nsproxy = init_task.nsproxy;
- get_task_namespaces(current);
+ if (current->nsproxy != init_task.nsproxy) {
+ get_nsproxy(init_task.nsproxy);
+ switch_task_namespaces(current, init_task.nsproxy);
+ }
exit_files(current);
current->files = init_task.files;
diff --git a/kernel/fork.c b/kernel/fork.c
index 2deaf481efa..d2f4a420a5b 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1632,7 +1632,7 @@ asmlinkage long sys_unshare(unsigned long unshare_flags)
struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
struct files_struct *fd, *new_fd = NULL;
struct sem_undo_list *new_ulist = NULL;
- struct nsproxy *new_nsproxy = NULL, *old_nsproxy = NULL;
+ struct nsproxy *new_nsproxy = NULL;
check_unshare_flags(&unshare_flags);
@@ -1662,14 +1662,13 @@ asmlinkage long sys_unshare(unsigned long unshare_flags)
if (new_fs || new_mm || new_fd || new_ulist || new_nsproxy) {
- task_lock(current);
-
if (new_nsproxy) {
- old_nsproxy = current->nsproxy;
- current->nsproxy = new_nsproxy;
- new_nsproxy = old_nsproxy;
+ switch_task_namespaces(current, new_nsproxy);
+ new_nsproxy = NULL;
}
+ task_lock(current);
+
if (new_fs) {
fs = current->fs;
current->fs = new_fs;
diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
index e981c61304f..c8ef7c2992e 100644
--- a/kernel/nsproxy.c
+++ b/kernel/nsproxy.c
@@ -26,19 +26,6 @@ static struct kmem_cache *nsproxy_cachep;
struct nsproxy init_nsproxy = INIT_NSPROXY(init_nsproxy);
-static inline void get_nsproxy(struct nsproxy *ns)
-{
- atomic_inc(&ns->count);
-}
-
-void get_task_namespaces(struct task_struct *tsk)
-{
- struct nsproxy *ns = tsk->nsproxy;
- if (ns) {
- get_nsproxy(ns);
- }
-}
-
/*
* creates a copy of "orig" with refcount 1.
*/
@@ -216,6 +203,33 @@ out:
return err;
}
+void switch_task_namespaces(struct task_struct *p, struct nsproxy *new)
+{
+ struct nsproxy *ns;
+
+ might_sleep();
+
+ ns = p->nsproxy;
+
+ rcu_assign_pointer(p->nsproxy, new);
+
+ if (ns && atomic_dec_and_test(&ns->count)) {
+ /*
+ * wait for others to get what they want from this nsproxy.
+ *
+ * cannot release this nsproxy via the call_rcu() since
+ * put_mnt_ns() will want to sleep
+ */
+ synchronize_rcu();
+ free_nsproxy(ns);
+ }
+}
+
+void exit_task_namespaces(struct task_struct *p)
+{
+ switch_task_namespaces(p, NULL);
+}
+
static int __init nsproxy_cache_init(void)
{
nsproxy_cachep = KMEM_CACHE(nsproxy, SLAB_PANIC);
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 1072d16696c..4a2640d3826 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -744,10 +744,10 @@ static struct net *get_net_ns_by_pid(pid_t pid)
rcu_read_lock();
tsk = find_task_by_pid(pid);
if (tsk) {
- task_lock(tsk);
- if (tsk->nsproxy)
- net = get_net(tsk->nsproxy->net_ns);
- task_unlock(tsk);
+ struct nsproxy *nsproxy;
+ nsproxy = task_nsproxy(tsk);
+ if (nsproxy)
+ net = get_net(nsproxy->net_ns);
}
rcu_read_unlock();
return net;