[PATCH review 06/16] userns: Allow unprivileged use of setns.

Eric W. Biederman
2012-11-19T15:13:19Z

- Push the permission check from the core setns syscall into
the setns install methods where the user namespace of the
target namespace can be determined, and used in a ns_capable
call.

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
ipc/namespace.c | 6 +++++-
kernel/nsproxy.c | 3 ---
kernel/utsname.c | 7 ++++++-
net/core/net_namespace.c | 7 ++++++-
4 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/ipc/namespace.c b/ipc/namespace.c
index f362298c..6ed33c0 100644
--- a/ipc/namespace.c
+++ b/ipc/namespace.c
@@ -161,8 +161,12 @@ static void ipcns_put(void *ns)
return put_ipc_ns(ns);
}

-static int ipcns_install(struct nsproxy *nsproxy, void *ns)
+static int ipcns_install(struct nsproxy *nsproxy, void *new)
{
+ struct ipc_namespace *ns = new;
+ if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN))
+ return -EPERM;
+
/* Ditch state from the old ipc namespace */
exit_sem(current);
put_ipc_ns(nsproxy->ipc_ns);
diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
index a214e0e..4357a0a 100644
--- a/kernel/nsproxy.c
+++ b/kernel/nsproxy.c
@@ -242,9 +242,6 @@ SYSCALL_DEFINE2(setns, int, fd, int, nstype)
struct file *file;
int err;

- if (!capable(CAP_SYS_ADMIN))
- return -EPERM;
-
file = proc_ns_fget(fd);
if (IS_ERR(file))
return PTR_ERR(file);
diff --git a/kernel/utsname.c b/kernel/utsname.c
index 679d97a..4a9362f 100644
--- a/kernel/utsname.c
+++ b/kernel/utsname.c
@@ -102,8 +102,13 @@ static void utsns_put(void *ns)
put_uts_ns(ns);
}

-static int utsns_install(struct nsproxy *nsproxy, void *ns)
+static int utsns_install(struct nsproxy *nsproxy, void *new)
{
+ struct uts_namespace *ns = new;
+
+ if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN))
+ return -EPERM;
+
get_uts_ns(ns);
put_uts_ns(nsproxy->uts_ns);
nsproxy->uts_ns = ns;
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index 6456439..ec2870b 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -630,8 +630,13 @@ static void netns_put(void *ns)

static int netns_install(struct nsproxy *nsproxy, void *ns)
{
+ struct net *net = ns;
+
+ if (!ns_capable(net->user_ns, CAP_SYS_ADMIN))
+ return -EPERM;
+
put_net(nsproxy->net_ns);
- nsproxy->net_ns = get_net(ns);
+ nsproxy->net_ns = get_net(net);
return 0;
}

--
1.7.5.4