devcgroup: always show positive major/minor num

 # echo "b $((0x7fffffff)):$((0x80000000)) rwm" > devices.allow
 # cat devices.list
 b 214748364:-21474836 rwm

though a major/minor number of 0x800000000 is meaningless, we
should not cast it to a negative value.
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
Acked-by: NSerge Hallyn <serue@us.ibm.com>
Cc: Serge Hallyn <serue@us.ibm.com>
Cc: Paul Menage <menage@google.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

security/device_cgroup.c

@@ -222,7 +222,7 @@ static void devcgroup_destroy(struct cgroup_subsys *ss,
 #define DEVCG_DENY 2
 #define DEVCG_LIST 3
 
-#define MAJMINLEN 10
+#define MAJMINLEN 13
 #define ACCLEN 4
 
 static void set_access(char *acc, short access)
@@ -254,7 +254,7 @@ static void set_majmin(char *str, unsigned m)
 	if (m == ~0)
 		sprintf(str, "*");
 	else
-		snprintf(str, MAJMINLEN, "%d", m);
+		snprintf(str, MAJMINLEN, "%u", m);
 }
 
 static int devcgroup_seq_read(struct cgroup *cgroup, struct cftype *cft,