ovl: hash overlay non-dir inodes by copy up origin

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

3 files changed, 44 insertions, 9 deletions

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 35bb956af8e8..d9fe07defca3 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -467,6 +467,25 @@ static int ovl_inode_set(struct inode *inode, void *data)
         return 0;
 }
 
+static bool ovl_verify_inode(struct inode *inode, struct dentry *lowerdentry,
+                             struct dentry *upperdentry)
+{
+        struct inode *lowerinode = lowerdentry ? d_inode(lowerdentry) : NULL;
+
+        /* Lower (origin) inode must match, even if NULL */
+        if (ovl_inode_lower(inode) != lowerinode)
+                return false;
+
+        /*
+         * Allow non-NULL __upperdentry in inode even if upperdentry is NULL.
+         * This happens when finding a lower alias for a copied up hard link.
+         */
+        if (upperdentry && ovl_inode_upper(inode) != d_inode(upperdentry))
+                return false;
+
+        return true;
+}
+
 struct inode *ovl_get_inode(struct dentry *dentry, struct dentry *upperdentry)
 {
         struct dentry *lowerdentry = ovl_dentry_lower(dentry);
@@ -476,12 +495,25 @@ struct inode *ovl_get_inode(struct dentry *dentry, struct dentry *upperdentry)
         if (!realinode)
                 realinode = d_inode(lowerdentry);
 
-        if (upperdentry && !d_is_dir(upperdentry)) {
-                inode = iget5_locked(dentry->d_sb, (unsigned long) realinode,
-                                     ovl_inode_test, ovl_inode_set, realinode);
+        if (!S_ISDIR(realinode->i_mode) &&
+            (upperdentry || (lowerdentry && ovl_indexdir(dentry->d_sb)))) {
+                struct inode *key = d_inode(lowerdentry ?: upperdentry);
+
+                inode = iget5_locked(dentry->d_sb, (unsigned long) key,
+                                     ovl_inode_test, ovl_inode_set, key);
                 if (!inode)
-                        goto out;
+                        goto out_nomem;
                 if (!(inode->i_state & I_NEW)) {
+                        /*
+                         * Verify that the underlying files stored in the inode
+                         * match those in the dentry.
+                         */
+                        if (!ovl_verify_inode(inode, lowerdentry, upperdentry)) {
+                                iput(inode);
+                                inode = ERR_PTR(-ESTALE);
+                                goto out;
+                        }
+
                         dput(upperdentry);
                         goto out;
                 }
@@ -490,7 +522,7 @@ struct inode *ovl_get_inode(struct dentry *dentry, struct dentry *upperdentry)
         } else {
                 inode = new_inode(dentry->d_sb);
                 if (!inode)
-                        goto out;
+                        goto out_nomem;
         }
         ovl_fill_inode(inode, realinode->i_mode, realinode->i_rdev);
         ovl_inode_init(inode, upperdentry, lowerdentry);
@@ -502,4 +534,8 @@ struct inode *ovl_get_inode(struct dentry *dentry, struct dentry *upperdentry)
                 unlock_new_inode(inode);
 out:
         return inode;
+
+out_nomem:
+        inode = ERR_PTR(-ENOMEM);
+        goto out;
 }
diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index 4df37e805eb7..f7fb0c919419 100644
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -678,9 +678,9 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
                 upperdentry = dget(index);
 
         if (upperdentry || ctr) {
-                err = -ENOMEM;
                 inode = ovl_get_inode(dentry, upperdentry);
-                if (!inode)
+                err = PTR_ERR(inode);
+                if (IS_ERR(inode))
                         goto out_free_oe;
 
                 OVL_I(inode)->redirect = upperredirect;
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index 90b50b8e75ab..22ed51f80e58 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -236,7 +236,6 @@ void ovl_inode_update(struct inode *inode, struct dentry *upperdentry)
 {
         struct inode *upperinode = d_inode(upperdentry);
 
-        WARN_ON(!inode_unhashed(inode));
         WARN_ON(!inode_is_locked(upperdentry->d_parent->d_inode));
         WARN_ON(OVL_I(inode)->__upperdentry);
 
@@ -245,7 +244,7 @@ void ovl_inode_update(struct inode *inode, struct dentry *upperdentry)
          */
         smp_wmb();
         OVL_I(inode)->__upperdentry = upperdentry;
-        if (!S_ISDIR(upperinode->i_mode)) {
+        if (!S_ISDIR(upperinode->i_mode) && inode_unhashed(inode)) {
                 inode->i_private = upperinode;
                 __insert_inode_hash(inode, (unsigned long) upperinode);
         }