3 files changed, 38 insertions, 57 deletions

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index d58a958444ab..095248082b7e 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -226,6 +226,12 @@ struct cftype {
          */
         int (*read_map) (struct cgroup *cont, struct cftype *cft,
                          struct cgroup_map_cb *cb);
+        /*
+         * read_seq_string() is used for outputting a simple sequence
+         * using seqfile.
+         */
+        int (*read_seq_string) (struct cgroup *cont, struct cftype *cft,
+                         struct seq_file *m);
 
         ssize_t (*write) (struct cgroup *cgrp, struct cftype *cft,
                           struct file *file,
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index aeceb8868981..abc433772e5a 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1549,11 +1549,14 @@ static int cgroup_seqfile_show(struct seq_file *m, void *arg)
 {
         struct cgroup_seqfile_state *state = m->private;
         struct cftype *cft = state->cft;
-        struct cgroup_map_cb cb = {
-                .fill = cgroup_map_add,
-                .state = m,
-        };
-        return cft->read_map(state->cgroup, cft, &cb);
+        if (cft->read_map) {
+                struct cgroup_map_cb cb = {
+                        .fill = cgroup_map_add,
+                        .state = m,
+                };
+                return cft->read_map(state->cgroup, cft, &cb);
+        }
+        return cft->read_seq_string(state->cgroup, cft, m);
 }
 
 int cgroup_seqfile_release(struct inode *inode, struct file *file)
@@ -1581,7 +1584,7 @@ static int cgroup_file_open(struct inode *inode, struct file *file)
         cft = __d_cft(file->f_dentry);
         if (!cft)
                 return -ENODEV;
-        if (cft->read_map) {
+        if (cft->read_map || cft->read_seq_string) {
                 struct cgroup_seqfile_state *state =
                         kzalloc(sizeof(*state), GFP_USER);
                 if (!state)
diff --git a/security/device_cgroup.c b/security/device_cgroup.c
index 4237b19e8fb3..4ea583689eec 100644
--- a/security/device_cgroup.c
+++ b/security/device_cgroup.c
@@ -9,6 +9,7 @@
 #include <linux/ctype.h>
 #include <linux/list.h>
 #include <linux/uaccess.h>
+#include <linux/seq_file.h>
 
 #define ACC_MKNOD 1
 #define ACC_READ  2
@@ -201,11 +202,15 @@ static void devcgroup_destroy(struct cgroup_subsys *ss,
 
 #define DEVCG_ALLOW 1
 #define DEVCG_DENY 2
+#define DEVCG_LIST 3
+
+#define MAJMINLEN 10
+#define ACCLEN 4
 
 static void set_access(char *acc, short access)
 {
         int idx = 0;
-        memset(acc, 0, 4);
+        memset(acc, 0, ACCLEN);
         if (access & ACC_READ)
                 acc[idx++] = 'r';
         if (access & ACC_WRITE)
@@ -225,70 +230,33 @@ static char type_to_char(short type)
         return 'X';
 }
 
-static void set_majmin(char *str, int len, unsigned m)
+static void set_majmin(char *str, unsigned m)
 {
-        memset(str, 0, len);
+        memset(str, 0, MAJMINLEN);
         if (m == ~0)
                 sprintf(str, "*");
         else
-                snprintf(str, len, "%d", m);
+                snprintf(str, MAJMINLEN, "%d", m);
 }
 
-static char *print_whitelist(struct dev_cgroup *devcgroup, int *len)
+static int devcgroup_seq_read(struct cgroup *cgroup, struct cftype *cft,
+                                struct seq_file *m)
 {
-        char *buf, *s, acc[4];
+        struct dev_cgroup *devcgroup = cgroup_to_devcgroup(cgroup);
         struct dev_whitelist_item *wh;
-        int ret;
-        int count = 0;
-        char maj[10], min[10];
-
-        buf = kmalloc(4096, GFP_KERNEL);
-        if (!buf)
-                return ERR_PTR(-ENOMEM);
-        s = buf;
-        *s = '\0';
-        *len = 0;
+        char maj[MAJMINLEN], min[MAJMINLEN], acc[ACCLEN];
 
         spin_lock(&devcgroup->lock);
         list_for_each_entry(wh, &devcgroup->whitelist, list) {
                 set_access(acc, wh->access);
-                set_majmin(maj, 10, wh->major);
-                set_majmin(min, 10, wh->minor);
-                ret = snprintf(s, 4095-(s-buf), "%c %s:%s %s\n",
-                        type_to_char(wh->type), maj, min, acc);
-                if (s+ret >= buf+4095) {
-                        kfree(buf);
-                        buf = ERR_PTR(-ENOMEM);
-                        break;
-                }
-                s += ret;
-                *len += ret;
-                count++;
+                set_majmin(maj, wh->major);
+                set_majmin(min, wh->minor);
+                seq_printf(m, "%c %s:%s %s\n", type_to_char(wh->type),
+                           maj, min, acc);
         }
         spin_unlock(&devcgroup->lock);
 
-        return buf;
-}
-
-static ssize_t devcgroup_access_read(struct cgroup *cgroup,
-                        struct cftype *cft, struct file *file,
-                        char __user *userbuf, size_t nbytes, loff_t *ppos)
-{
-        struct dev_cgroup *devcgroup = cgroup_to_devcgroup(cgroup);
-        int filetype = cft->private;
-        char *buffer;
-        int uninitialized_var(len);
-        int retval;
-
-        if (filetype != DEVCG_ALLOW)
-                return -EINVAL;
-        buffer = print_whitelist(devcgroup, &len);
-        if (IS_ERR(buffer))
-                return PTR_ERR(buffer);
-
-        retval = simple_read_from_buffer(userbuf, nbytes, ppos, buffer, len);
-        kfree(buffer);
-        return retval;
+        return 0;
 }
 
 /*
@@ -501,7 +469,6 @@ out1:
 static struct cftype dev_cgroup_files[] = {
         {
                 .name = "allow",
-                .read = devcgroup_access_read,
                 .write  = devcgroup_access_write,
                 .private = DEVCG_ALLOW,
         },
@@ -510,6 +477,11 @@ static struct cftype dev_cgroup_files[] = {
                 .write = devcgroup_access_write,
                 .private = DEVCG_DENY,
         },
+        {
+                .name = "list",
+                .read_seq_string = devcgroup_seq_read,
+                .private = DEVCG_LIST,
+        },
 };
 
 static int devcgroup_populate(struct cgroup_subsys *ss,