[RFC PATCH 05/14] userns: clamp down users of cap_raised

[Serge Hallyn <serge@hallyn.com>]

From: Serge E. Hallyn <serge.hallyn@canonical.com>

A few modules are using cap_raised(current_cap(), cap) to authorize
actions, but the privilege should be applicable against the initial
user namespace.  Refuse privilege if the caller is not in init_user_ns.

Signed-off-by: Serge E. Hallyn <serge.hallyn@canonical.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
---
 drivers/block/drbd/drbd_nl.c           |    5 +++++
 drivers/md/dm-log-userspace-transfer.c |    3 +++
 drivers/staging/pohmelfs/config.c      |    3 +++
 drivers/video/uvesafb.c                |    3 +++
 4 files changed, 14 insertions(+), 0 deletions(-)

diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 515bcd9..7717f8a 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -2297,6 +2297,11 @@ static void drbd_connector_callback(struct cn_msg *req, struct netlink_skb_parms
 		return;
 	}
 
+	if (current_user_ns() != &init_user_ns) {
+		retcode = ERR_PERM;
+		goto fail;
+	}
+
 	if (!cap_raised(current_cap(), CAP_SYS_ADMIN)) {
 		retcode = ERR_PERM;
 		goto fail;
diff --git a/drivers/md/dm-log-userspace-transfer.c b/drivers/md/dm-log-userspace-transfer.c
index 1f23e04..140ca81 100644
--- a/drivers/md/dm-log-userspace-transfer.c
+++ b/drivers/md/dm-log-userspace-transfer.c
@@ -134,6 +134,9 @@ static void cn_ulog_callback(struct cn_msg *msg, struct netlink_skb_parms *nsp)
 {
 	struct dm_ulog_request *tfr = (struct dm_ulog_request *)(msg + 1);
 
+	if (current_user_ns() != &init_user_ns)
+		return;
+
 	if (!cap_raised(current_cap(), CAP_SYS_ADMIN))
 		return;
 
diff --git a/drivers/staging/pohmelfs/config.c b/drivers/staging/pohmelfs/config.c
index b6c42cb..cd259d0 100644
--- a/drivers/staging/pohmelfs/config.c
+++ b/drivers/staging/pohmelfs/config.c
@@ -525,6 +525,9 @@ static void pohmelfs_cn_callback(struct cn_msg *msg, struct netlink_skb_parms *n
 {
 	int err;
 
+	if (current_user_ns() != &init_user_ns)
+		return;
+
 	if (!cap_raised(current_cap(), CAP_SYS_ADMIN))
 		return;
 
diff --git a/drivers/video/uvesafb.c b/drivers/video/uvesafb.c
index 7f8472c..71dab8e 100644
--- a/drivers/video/uvesafb.c
+++ b/drivers/video/uvesafb.c
@@ -73,6 +73,9 @@ static void uvesafb_cn_callback(struct cn_msg *msg, struct netlink_skb_parms *ns
 	struct uvesafb_task *utask;
 	struct uvesafb_ktask *task;
 
+	if (current_user_ns() != &init_user_ns)
+		return;
+
 	if (!cap_raised(current_cap(), CAP_SYS_ADMIN))
 		return;
 
-- 
1.7.4.1