devcgroup: fix odd behaviour when writing 'a' to devices.allow

 # cat /devcg/devices.list
 a *:* rwm
 # echo a > devices.allow
 # cat /devcg/devices.list
 a *:* rwm
 a 0:0 rwm

This is odd and maybe confusing.  With this patch, writing 'a' to
devices.allow will add 'a *:* rwm' to the whitelist.

Also a few fixes and updates to the document.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Serge E. Hallyn <serue@us.ibm.com>
Cc: Paul Menage <menage@google.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: James Morris <jmorris@namei.org>
Cc: Chris Wright <chrisw@sous-sol.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/security/device_cgroup.c b/security/device_cgroup.c
index baf348834b66..fd764a0858d0 100644
--- a/security/device_cgroup.c
+++ b/security/device_cgroup.c
@@ -382,6 +382,8 @@ static ssize_t devcgroup_access_write(struct cgroup *cgroup, struct cftype *cft,
         case 'a':
                 wh.type = DEV_ALL;
                 wh.access = ACC_MASK;
+                wh.major = ~0;
+                wh.minor = ~0;
                 goto handle;
         case 'b':
                 wh.type = DEV_BLOCK;