Merge tag 'driver-core-3.15-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core

Pull driver core fixes from Greg KH:
 "Here are two driver core (well, sysfs) fixes for 3.15-rc6 that resolve
  some reported issues and a regression from 3.13"

* tag 'driver-core-3.15-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core:
  sysfs: make sure read buffer is zeroed
  kernfs, sysfs, cgroup: restrict extra perm check on open to sysfs

3 files changed, 14 insertions, 9 deletions

diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index e01ea4a14a01..5e9a80cfc3d8 100644
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -610,6 +610,7 @@ static void kernfs_put_open_node(struct kernfs_node *kn,
 static int kernfs_fop_open(struct inode *inode, struct file *file)
 {
         struct kernfs_node *kn = file->f_path.dentry->d_fsdata;
+        struct kernfs_root *root = kernfs_root(kn);
         const struct kernfs_ops *ops;
         struct kernfs_open_file *of;
         bool has_read, has_write, has_mmap;
@@ -624,14 +625,16 @@ static int kernfs_fop_open(struct inode *inode, struct file *file)
         has_write = ops->write || ops->mmap;
         has_mmap = ops->mmap;
 
-        /* check perms and supported operations */
-        if ((file->f_mode & FMODE_WRITE) &&
-            (!(inode->i_mode & S_IWUGO) || !has_write))
-                goto err_out;
+        /* see the flag definition for details */
+        if (root->flags & KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK) {
+                if ((file->f_mode & FMODE_WRITE) &&
+                    (!(inode->i_mode & S_IWUGO) || !has_write))
+                        goto err_out;
 
-        if ((file->f_mode & FMODE_READ) &&
-            (!(inode->i_mode & S_IRUGO) || !has_read))
-                goto err_out;
+                if ((file->f_mode & FMODE_READ) &&
+                    (!(inode->i_mode & S_IRUGO) || !has_read))
+                        goto err_out;
+        }
 
         /* allocate a kernfs_open_file for the file */
         error = -ENOMEM;
diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index 28cc1acd5439..e9ef59b3abb1 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -47,12 +47,13 @@ static int sysfs_kf_seq_show(struct seq_file *sf, void *v)
         ssize_t count;
         char *buf;
 
-        /* acquire buffer and ensure that it's >= PAGE_SIZE */
+        /* acquire buffer and ensure that it's >= PAGE_SIZE and clear */
         count = seq_get_buf(sf, &buf);
         if (count < PAGE_SIZE) {
                 seq_commit(sf, -1);
                 return 0;
         }
+        memset(buf, 0, PAGE_SIZE);
 
         /*
          * Invoke show().  Control may reach here via seq file lseek even
diff --git a/fs/sysfs/mount.c b/fs/sysfs/mount.c
index a66ad6196f59..8794423f7efb 100644
--- a/fs/sysfs/mount.c
+++ b/fs/sysfs/mount.c
@@ -63,7 +63,8 @@ int __init sysfs_init(void)
 {
         int err;
 
-        sysfs_root = kernfs_create_root(NULL, 0, NULL);
+        sysfs_root = kernfs_create_root(NULL, KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK,
+                                        NULL);
         if (IS_ERR(sysfs_root))
                 return PTR_ERR(sysfs_root);