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pidns: Capture the user namespace and filter ns_last_pid

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- Capture the the user namespace that creates the pid namespace
- Use that user namespace to test if it is ok to write to
  /proc/sys/kernel/ns_last_pid.

Zhao Hongjiang <zhaohongjiang@huawei.com> noticed I was missing a put_user_ns
in when destroying a pid_ns.  I have foloded his patch into this one
so that bisects will work properly.

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman 2012-08-02 04:25:10 -07:00
parent ae06c7c83f
commit 49f4d8b93c
4 changed files with 19 additions and 9 deletions
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17
kernel/pid_namespace.c
View file

@ -10,6 +10,7 @@
#include <linux/pid.h>
#include <linux/pid_namespace.h>
#include <linux/user_namespace.h>
#include <linux/syscalls.h>
#include <linux/err.h>
#include <linux/acct.h>
@ -74,7 +75,8 @@ err_alloc:
/* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */
#define MAX_PID_NS_LEVEL 32
static struct pid_namespace *create_pid_namespace(struct pid_namespace *parent_pid_ns)
static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns,
struct pid_namespace *parent_pid_ns)
{
struct pid_namespace *ns;
unsigned int level = parent_pid_ns->level + 1;
@ -102,6 +104,7 @@ static struct pid_namespace *create_pid_namespace(struct pid_namespace *parent_p
kref_init(&ns->kref);
ns->level = level;
ns->parent = get_pid_ns(parent_pid_ns);
ns->user_ns = get_user_ns(user_ns);
set_bit(0, ns->pidmap[0].page);
atomic_set(&ns->pidmap[0].nr_free, BITS_PER_PAGE - 1);
@ -117,6 +120,7 @@ static struct pid_namespace *create_pid_namespace(struct pid_namespace *parent_p
out_put_parent_pid_ns:
put_pid_ns(parent_pid_ns);
put_user_ns(user_ns);
out_free_map:
kfree(ns->pidmap[0].page);
out_free:
@ -131,16 +135,18 @@ static void destroy_pid_namespace(struct pid_namespace *ns)
for (i = 0; i < PIDMAP_ENTRIES; i++)
kfree(ns->pidmap[i].page);
put_user_ns(ns->user_ns);
kmem_cache_free(pid_ns_cachep, ns);
}
struct pid_namespace *copy_pid_ns(unsigned long flags, struct pid_namespace *old_ns)
struct pid_namespace *copy_pid_ns(unsigned long flags,
struct user_namespace *user_ns, struct pid_namespace *old_ns)
{
if (!(flags & CLONE_NEWPID))
return get_pid_ns(old_ns);
if (flags & (CLONE_THREAD|CLONE_PARENT))
return ERR_PTR(-EINVAL);
return create_pid_namespace(old_ns);
return create_pid_namespace(user_ns, old_ns);
}
static void free_pid_ns(struct kref *kref)
@ -239,9 +245,10 @@ void zap_pid_ns_processes(struct pid_namespace *pid_ns)
static int pid_ns_ctl_handler(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
struct pid_namespace *pid_ns = task_active_pid_ns(current);
struct ctl_table tmp = *table;
if (write && !capable(CAP_SYS_ADMIN))
if (write && !ns_capable(pid_ns->user_ns, CAP_SYS_ADMIN))
return -EPERM;
/*
@ -250,7 +257,7 @@ static int pid_ns_ctl_handler(struct ctl_table *table, int write,
* it should synchronize its usage with external means.
*/
tmp.data = &current->nsproxy->pid_ns->last_pid;
tmp.data = &pid_ns->last_pid;
return proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
}