Merge branch 'overlayfs-next' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs

Pull two overlayfs fixes from Miklos Szeredi:
 "Overlayfs rmdir() failed to check for emptiness in one case; this was
  introduced in 4.0.  The other bug was there since day one: failure to
  mount if upper fs is full, which bit some OpenWRT folks"

* 'overlayfs-next' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
  ovl: mount read-only if workdir can't be created
  ovl: don't remove non-empty opaque directory

3 files changed, 36 insertions, 10 deletions

diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index 24f640441bd9..84d693d37428 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -299,6 +299,9 @@ int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
         struct cred *override_cred;
         char *link = NULL;
 
+        if (WARN_ON(!workdir))
+                return -EROFS;
+
         ovl_path_upper(parent, &parentpath);
         upperdir = parentpath.dentry;
 
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index d139405d2bfa..692ceda3bc21 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -222,6 +222,9 @@ static struct dentry *ovl_clear_empty(struct dentry *dentry,
         struct kstat stat;
         int err;
 
+        if (WARN_ON(!workdir))
+                return ERR_PTR(-EROFS);
+
         err = ovl_lock_rename_workdir(workdir, upperdir);
         if (err)
                 goto out;
@@ -322,6 +325,9 @@ static int ovl_create_over_whiteout(struct dentry *dentry, struct inode *inode,
         struct dentry *newdentry;
         int err;
 
+        if (WARN_ON(!workdir))
+                return -EROFS;
+
         err = ovl_lock_rename_workdir(workdir, upperdir);
         if (err)
                 goto out;
@@ -506,11 +512,28 @@ static int ovl_remove_and_whiteout(struct dentry *dentry, bool is_dir)
         struct dentry *opaquedir = NULL;
         int err;
 
-        if (is_dir && OVL_TYPE_MERGE_OR_LOWER(ovl_path_type(dentry))) {
-                opaquedir = ovl_check_empty_and_clear(dentry);
-                err = PTR_ERR(opaquedir);
-                if (IS_ERR(opaquedir))
-                        goto out;
+        if (WARN_ON(!workdir))
+                return -EROFS;
+
+        if (is_dir) {
+                if (OVL_TYPE_MERGE_OR_LOWER(ovl_path_type(dentry))) {
+                        opaquedir = ovl_check_empty_and_clear(dentry);
+                        err = PTR_ERR(opaquedir);
+                        if (IS_ERR(opaquedir))
+                                goto out;
+                } else {
+                        LIST_HEAD(list);
+
+                        /*
+                         * When removing an empty opaque directory, then it
+                         * makes no sense to replace it with an exact replica of
+                         * itself.  But emptiness still needs to be checked.
+                         */
+                        err = ovl_check_empty_dir(dentry, &list);
+                        ovl_cache_free(&list);
+                        if (err)
+                                goto out;
+                }
         }
 
         err = ovl_lock_rename_workdir(workdir, upperdir);
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 5f0d1993e6e3..bf8537c7f455 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -529,7 +529,7 @@ static int ovl_remount(struct super_block *sb, int *flags, char *data)
 {
         struct ovl_fs *ufs = sb->s_fs_info;
 
-        if (!(*flags & MS_RDONLY) && !ufs->upper_mnt)
+        if (!(*flags & MS_RDONLY) && (!ufs->upper_mnt || !ufs->workdir))
                 return -EROFS;
 
         return 0;
@@ -925,9 +925,10 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
                 ufs->workdir = ovl_workdir_create(ufs->upper_mnt, workpath.dentry);
                 err = PTR_ERR(ufs->workdir);
                 if (IS_ERR(ufs->workdir)) {
-                        pr_err("overlayfs: failed to create directory %s/%s\n",
-                               ufs->config.workdir, OVL_WORKDIR_NAME);
-                        goto out_put_upper_mnt;
+                        pr_warn("overlayfs: failed to create directory %s/%s (errno: %i); mounting read-only\n",
+                                ufs->config.workdir, OVL_WORKDIR_NAME, -err);
+                        sb->s_flags |= MS_RDONLY;
+                        ufs->workdir = NULL;
                 }
         }
 
@@ -997,7 +998,6 @@ out_put_lower_mnt:
         kfree(ufs->lower_mnt);
 out_put_workdir:
         dput(ufs->workdir);
-out_put_upper_mnt:
         mntput(ufs->upper_mnt);
 out_put_lowerpath:
         for (i = 0; i < numlower; i++)