2 files changed, 41 insertions, 21 deletions

diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index 2fbdff6be25c..e8e0e71b29d5 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -165,21 +165,8 @@ struct sysfs_dirent *sysfs_get_active(struct sysfs_dirent *sd)
         if (unlikely(!sd))
                 return NULL;
 
-        while (1) {
-                int v, t;
-
-                v = atomic_read(&sd->s_active);
-                if (unlikely(v < 0))
-                        return NULL;
-
-                t = atomic_cmpxchg(&sd->s_active, v, v + 1);
-                if (likely(t == v))
-                        break;
-                if (t < 0)
-                        return NULL;
-
-                cpu_relax();
-        }
+        if (!atomic_inc_unless_negative(&sd->s_active))
+                return NULL;
 
         if (likely(!ignore_lockdep(sd)))
                 rwsem_acquire_read(&sd->dep_map, 0, 1, _RET_IP_);
@@ -281,6 +268,10 @@ void release_sysfs_dirent(struct sysfs_dirent * sd)
          */
         parent_sd = sd->s_parent;
 
+        WARN(!(sd->s_flags & SYSFS_FLAG_REMOVED),
+                "sysfs: free using entry: %s/%s\n",
+                parent_sd ? parent_sd->s_name : "", sd->s_name);
+
         if (sysfs_type(sd) == SYSFS_KOBJ_LINK)
                 sysfs_put(sd->s_symlink.target_sd);
         if (sysfs_type(sd) & SYSFS_COPY_NAME)
@@ -399,7 +390,7 @@ struct sysfs_dirent *sysfs_new_dirent(const char *name, umode_t mode, int type)
 
         sd->s_name = name;
         sd->s_mode = mode;
-        sd->s_flags = type;
+        sd->s_flags = type | SYSFS_FLAG_REMOVED;
 
         return sd;
 
@@ -479,6 +470,9 @@ int __sysfs_add_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd)
                 ps_iattrs->ia_ctime = ps_iattrs->ia_mtime = CURRENT_TIME;
         }
 
+        /* Mark the entry added into directory tree */
+        sd->s_flags &= ~SYSFS_FLAG_REMOVED;
+
         return 0;
 }
 
@@ -1012,6 +1006,7 @@ static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir)
         enum kobj_ns_type type;
         const void *ns;
         ino_t ino;
+        loff_t off;
 
         type = sysfs_ns_type(parent_sd);
         ns = sysfs_info(dentry->d_sb)->ns[type];
@@ -1020,6 +1015,8 @@ static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir)
                 ino = parent_sd->s_ino;
                 if (filldir(dirent, ".", 1, filp->f_pos, ino, DT_DIR) == 0)
                         filp->f_pos++;
+                else
+                        return 0;
         }
         if (filp->f_pos == 1) {
                 if (parent_sd->s_parent)
@@ -1028,8 +1025,11 @@ static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir)
                         ino = parent_sd->s_ino;
                 if (filldir(dirent, "..", 2, filp->f_pos, ino, DT_DIR) == 0)
                         filp->f_pos++;
+                else
+                        return 0;
         }
         mutex_lock(&sysfs_mutex);
+        off = filp->f_pos;
         for (pos = sysfs_dir_pos(ns, parent_sd, filp->f_pos, pos);
              pos;
              pos = sysfs_dir_next_pos(ns, parent_sd, filp->f_pos, pos)) {
@@ -1041,27 +1041,43 @@ static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir)
                 len = strlen(name);
                 ino = pos->s_ino;
                 type = dt_type(pos);
-                filp->f_pos = pos->s_hash;
+                off = filp->f_pos = pos->s_hash;
                 filp->private_data = sysfs_get(pos);
 
                 mutex_unlock(&sysfs_mutex);
-                ret = filldir(dirent, name, len, filp->f_pos, ino, type);
+                ret = filldir(dirent, name, len, off, ino, type);
                 mutex_lock(&sysfs_mutex);
                 if (ret < 0)
                         break;
         }
         mutex_unlock(&sysfs_mutex);
-        if ((filp->f_pos > 1) && !pos) { /* EOF */
-                filp->f_pos = INT_MAX;
+
+        /* don't reference last entry if its refcount is dropped */
+        if (!pos) {
                 filp->private_data = NULL;
+
+                /* EOF and not changed as 0 or 1 in read/write path */
+                if (off == filp->f_pos && off > 1)
+                        filp->f_pos = INT_MAX;
         }
         return 0;
 }
 
+static loff_t sysfs_dir_llseek(struct file *file, loff_t offset, int whence)
+{
+        struct inode *inode = file_inode(file);
+        loff_t ret;
+
+        mutex_lock(&inode->i_mutex);
+        ret = generic_file_llseek(file, offset, whence);
+        mutex_unlock(&inode->i_mutex);
+
+        return ret;
+}
 
 const struct file_operations sysfs_dir_operations = {
         .read           = generic_read_dir,
         .readdir        = sysfs_readdir,
         .release        = sysfs_dir_release,
-        .llseek         = generic_file_llseek,
+        .llseek         = sysfs_dir_llseek,
 };
diff --git a/fs/sysfs/mount.c b/fs/sysfs/mount.c
index 8d924b5ec733..afd83273e6ce 100644
--- a/fs/sysfs/mount.c
+++ b/fs/sysfs/mount.c
@@ -19,6 +19,7 @@
 #include <linux/module.h>
 #include <linux/magic.h>
 #include <linux/slab.h>
+#include <linux/user_namespace.h>
 
 #include "sysfs.h"
 
@@ -111,6 +112,9 @@ static struct dentry *sysfs_mount(struct file_system_type *fs_type,
         struct super_block *sb;
         int error;
 
+        if (!(flags & MS_KERNMOUNT) && !current_user_ns()->may_mount_sysfs)
+                return ERR_PTR(-EPERM);
+
         info = kzalloc(sizeof(*info), GFP_KERNEL);
         if (!info)
                 return ERR_PTR(-ENOMEM);