ovl: proper cleanup of workdir

When mounting overlayfs it needs a clean "work" directory under the
supplied workdir.

Previously the mount code removed this directory if it already existed and
created a new one.  If the removal failed (e.g. directory was not empty)
then it fell back to a read-only mount not using the workdir.

While this has never been reported, it is possible to get a non-empty
"work" dir from a previous mount of overlayfs in case of crash in the
middle of an operation using the work directory.

In this case the left over state should be discarded and the overlay
filesystem will be consistent, guaranteed by the atomicity of operations on
moving to/from the workdir to the upper layer.

This patch implements cleaning out any files left in workdir.  It is
implemented using real recursion for simplicity, but the depth is limited
to 2, because the worst case is that of a directory containing whiteouts
under "work".

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Cc: <stable@vger.kernel.org>
Orabug: 26401569

(backport upstream commit eea2fb4851e9dcbab6b991aaf47e2e024f1f55a0)

Signed-off-by: Shan Hai <shan.hai@oracle.com>
Reviewed-by: Somasundaram Krishnasamy <somasundaram.krishnasamy@oracle.com>

diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 3ef63f93875c0b92a80ea86c6a68b8e0ecefc78d..a564973bb7f1bbc1cc47ae4e1a103bf1941d1cc5 100644 (file)
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -179,6 +179,8 @@ int ovl_check_empty_dir(struct dentry *dentry, struct list_head *list);
 void ovl_cleanup_whiteouts(struct dentry *upper, struct list_head *list);
 void ovl_cache_free(struct list_head *list);
 int ovl_check_d_type_supported(struct path *realpath);
+void ovl_workdir_cleanup(struct inode *dir, struct vfsmount *mnt,
+                        struct dentry *dentry, int level);
 
 /* inode.c */
 int ovl_setattr(struct dentry *dentry, struct iattr *attr);

diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c
index d60897d2d8e8da8a279af96102ea9be3aeabf810..3f4db095d7b9f06918586533e00314947ea619f4 100644 (file)
--- a/fs/overlayfs/readdir.c
+++ b/fs/overlayfs/readdir.c
@@ -248,7 +248,7 @@ static inline int ovl_dir_read(struct path *realpath,
                        err = rdd->err;
        } while (!err && rdd->count);
 
-       if (!err && rdd->first_maybe_whiteout)
+       if (!err && rdd->first_maybe_whiteout && rdd->dentry)
                err = ovl_check_whiteouts(realpath->dentry, rdd);
 
        fput(realfile);
@@ -606,3 +606,64 @@ int ovl_check_d_type_supported(struct path *realpath)
 
        return rdd.d_type_supported;
 }
+
+static void ovl_workdir_cleanup_recurse(struct path *path, int level)
+{
+       int err;
+       struct inode *dir = path->dentry->d_inode;
+       LIST_HEAD(list);
+       struct ovl_cache_entry *p;
+       struct ovl_readdir_data rdd = {
+               .ctx.actor = ovl_fill_merge,
+               .dentry = NULL,
+               .list = &list,
+               .root = RB_ROOT,
+               .is_lowest = false,
+       };
+
+       err = ovl_dir_read(path, &rdd);
+       if (err)
+               goto out;
+
+       inode_lock_nested(dir, I_MUTEX_PARENT);
+       list_for_each_entry(p, &list, l_node) {
+               struct dentry *dentry;
+
+               if (p->name[0] == '.') {
+                       if (p->len == 1)
+                               continue;
+                       if (p->len == 2 && p->name[1] == '.')
+                               continue;
+               }
+               dentry = lookup_one_len(p->name, path->dentry, p->len);
+               if (IS_ERR(dentry))
+                       continue;
+               if (dentry->d_inode)
+                       ovl_workdir_cleanup(dir, path->mnt, dentry, level);
+               dput(dentry);
+       }
+       inode_unlock(dir);
+out:
+       ovl_cache_free(&list);
+}
+
+void ovl_workdir_cleanup(struct inode *dir, struct vfsmount *mnt,
+                        struct dentry *dentry, int level)
+{
+       int err;
+
+       if (!d_is_dir(dentry) || level > 1) {
+               ovl_cleanup(dir, dentry);
+               return;
+       }
+
+       err = ovl_do_rmdir(dir, dentry);
+       if (err) {
+               struct path path = { .mnt = mnt, .dentry = dentry };
+
+               inode_unlock(dir);
+               ovl_workdir_cleanup_recurse(&path, level + 1);
+               inode_lock_nested(dir, I_MUTEX_PARENT);
+               ovl_cleanup(dir, dentry);
+       }
+}

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 404195531847d4ff9d78657c3bdc8e14217ce52b..902119e0a9d03fe4a45687769fa84186184f3d04 100644 (file)
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -708,7 +708,7 @@ retry:
                                goto out_dput;
 
                        retried = true;
-                       ovl_cleanup(dir, work);
+                       ovl_workdir_cleanup(dir, mnt, work, 0);
                        dput(work);
                        goto retry;
                }