debugfs: leave freeing a symlink body until inode eviction

As it is, we have debugfs_remove() racing with symlink traversals.
Supply ->evict_inode() and do freeing there - inode will remain
pinned until we are done with the symlink body.

And rip the idiocy with checking if dentry is positive right after
we'd verified debugfs_positive(), which is a stronger check...

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

1 files changed, 17 insertions, 17 deletions

diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index 90933645298c..96400ab42d13 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -169,10 +169,19 @@ static int debugfs_show_options(struct seq_file *m, struct dentry *root)
         return 0;
 }
 
+static void debugfs_evict_inode(struct inode *inode)
+{
+        truncate_inode_pages_final(&inode->i_data);
+        clear_inode(inode);
+        if (S_ISLNK(inode->i_mode))
+                kfree(inode->i_private);
+}
+
 static const struct super_operations debugfs_super_operations = {
         .statfs         = simple_statfs,
         .remount_fs     = debugfs_remount,
         .show_options   = debugfs_show_options,
+        .evict_inode    = debugfs_evict_inode,
 };
 
 static struct vfsmount *debugfs_automount(struct path *path)
@@ -511,23 +520,14 @@ static int __debugfs_remove(struct dentry *dentry, struct dentry *parent)
         int ret = 0;
 
         if (debugfs_positive(dentry)) {
-                if (dentry->d_inode) {
-                        dget(dentry);
-                        switch (dentry->d_inode->i_mode & S_IFMT) {
-                        case S_IFDIR:
-                                ret = simple_rmdir(parent->d_inode, dentry);
-                                break;
-                        case S_IFLNK:
-                                kfree(dentry->d_inode->i_private);
-                                /* fall through */
-                        default:
-                                simple_unlink(parent->d_inode, dentry);
-                                break;
-                        }
-                        if (!ret)
-                                d_delete(dentry);
-                        dput(dentry);
-                }
+                dget(dentry);
+                if (S_ISDIR(dentry->d_inode->i_mode))
+                        ret = simple_rmdir(parent->d_inode, dentry);
+                else
+                        simple_unlink(parent->d_inode, dentry);
+                if (!ret)
+                        d_delete(dentry);
+                dput(dentry);
         }
         return ret;
 }