[PATCH] fix races and leaks in vfs_quota_on() users

* new helper: vfs_quota_on_path(); equivalent of vfs_quota_on() sans the
  pathname resolution.
* callers of vfs_quota_on() that do their own pathname resolution and
  checks based on it are switched to vfs_quota_on_path(); that way we
  avoid the races.
* reiserfs leaked dentry/vfsmount references on several failure exits.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 20 insertions, 13 deletions

diff --git a/fs/dquot.c b/fs/dquot.c
index 1346eebe74ce..8ec4d6cc7633 100644
--- a/fs/dquot.c
+++ b/fs/dquot.c
@@ -1793,6 +1793,21 @@ static int vfs_quota_on_remount(struct super_block *sb, int type)
         return ret;
 }
 
+int vfs_quota_on_path(struct super_block *sb, int type, int format_id,
+                      struct path *path)
+{
+        int error = security_quota_on(path->dentry);
+        if (error)
+                return error;
+        /* Quota file not on the same filesystem? */
+        if (path->mnt->mnt_sb != sb)
+                error = -EXDEV;
+        else
+                error = vfs_quota_on_inode(path->dentry->d_inode, type,
+                                           format_id);
+        return error;
+}
+
 /* Actual function called from quotactl() */
 int vfs_quota_on(struct super_block *sb, int type, int format_id, char *path,
                  int remount)
@@ -1804,19 +1819,10 @@ int vfs_quota_on(struct super_block *sb, int type, int format_id, char *path,
                 return vfs_quota_on_remount(sb, type);
 
         error = path_lookup(path, LOOKUP_FOLLOW, &nd);
-        if (error < 0)
-                return error;
-        error = security_quota_on(nd.path.dentry);
-        if (error)
-                goto out_path;
-        /* Quota file not on the same filesystem? */
-        if (nd.path.mnt->mnt_sb != sb)
-                error = -EXDEV;
-        else
-                error = vfs_quota_on_inode(nd.path.dentry->d_inode, type,
-                                           format_id);
-out_path:
-        path_put(&nd.path);
+        if (!error) {
+                error = vfs_quota_on_path(sb, type, format_id, &nd.path);
+                path_put(&nd.path);
+        }
         return error;
 }
 
@@ -2185,6 +2191,7 @@ EXPORT_SYMBOL(unregister_quota_format);
 EXPORT_SYMBOL(dqstats);
 EXPORT_SYMBOL(dq_data_lock);
 EXPORT_SYMBOL(vfs_quota_on);
+EXPORT_SYMBOL(vfs_quota_on_path);
 EXPORT_SYMBOL(vfs_quota_on_mount);
 EXPORT_SYMBOL(vfs_quota_off);
 EXPORT_SYMBOL(vfs_quota_sync);