Merge pull request #76 from toradex/4.9-2.3.x-imx

4.9 2.3.x imx

1 files changed, 13 insertions, 6 deletions

diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
index 5c5ff9f6fe07..2a5e436ff8dd 100644
--- a/fs/ecryptfs/inode.c
+++ b/fs/ecryptfs/inode.c
@@ -326,9 +326,9 @@ static int ecryptfs_i_size_read(struct dentry *dentry, struct inode *inode)
 static struct dentry *ecryptfs_lookup_interpose(struct dentry *dentry,
 				     struct dentry *lower_dentry)
 {
-	struct inode *inode, *lower_inode = d_inode(lower_dentry);
+	struct path *path = ecryptfs_dentry_to_lower_path(dentry->d_parent);
+	struct inode *inode, *lower_inode;
 	struct ecryptfs_dentry_info *dentry_info;
-	struct vfsmount *lower_mnt;
 	int rc = 0;
 
 	dentry_info = kmem_cache_alloc(ecryptfs_dentry_info_cache, GFP_KERNEL);
@@ -340,16 +340,23 @@ static struct dentry *ecryptfs_lookup_interpose(struct dentry *dentry,
 		return ERR_PTR(-ENOMEM);
 	}
 
-	lower_mnt = mntget(ecryptfs_dentry_to_lower_mnt(dentry->d_parent));
 	fsstack_copy_attr_atime(d_inode(dentry->d_parent),
-				d_inode(lower_dentry->d_parent));
+				d_inode(path->dentry));
 	BUG_ON(!d_count(lower_dentry));
 
 	ecryptfs_set_dentry_private(dentry, dentry_info);
-	dentry_info->lower_path.mnt = lower_mnt;
+	dentry_info->lower_path.mnt = mntget(path->mnt);
 	dentry_info->lower_path.dentry = lower_dentry;
 
-	if (d_really_is_negative(lower_dentry)) {
+	/*
+	 * negative dentry can go positive under us here - its parent is not
+	 * locked.  That's OK and that could happen just as we return from
+	 * ecryptfs_lookup() anyway.  Just need to be careful and fetch
+	 * ->d_inode only once - it's not stable here.
+	 */
+	lower_inode = READ_ONCE(lower_dentry->d_inode);
+
+	if (!lower_inode) {
 		/* We want to add because we couldn't find in lower */
 		d_add(dentry, NULL);
 		return NULL;