ovl: don't copy up opaqueness

[ Upstream commit 0956254a2d5b9e2141385514553aeef694dfe3b5 ]

When a copy up of a directory occurs which has the opaque xattr set, the
xattr remains in the upper directory. The immediate behavior with overlayfs
is that the upper directory is not treated as opaque, however after a
remount the opaque flag is used and upper directory is treated as opaque.
This causes files created in the lower layer to be hidden when using
multiple lower directories.

Fix by not copying up the opaque flag.

To reproduce:

 ----8<---------8<---------8<---------8<---------8<---------8<----
mkdir -p l/d/s u v w mnt
mount -t overlay overlay -olowerdir=l,upperdir=u,workdir=w mnt
rm -rf mnt/d/
mkdir -p mnt/d/n
umount mnt
mount -t overlay overlay -olowerdir=u:l,upperdir=v,workdir=w mnt
touch mnt/d/foo
umount mnt
mount -t overlay overlay -olowerdir=u:l,upperdir=v,workdir=w mnt
ls mnt/d
 ----8<---------8<---------8<---------8<---------8<---------8<----

output should be:  "foo  n"

Reported-by: Derek McGowan <dmcg@drizz.net>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=151291
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>

3 files changed, 4 insertions, 2 deletions

diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index 758012bfd5f0..4d8aa749d9b2 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -48,6 +48,8 @@ int ovl_copy_xattr(struct dentry *old, struct dentry *new)
 	}
 
 	for (name = buf; name < (buf + list_size); name += strlen(name) + 1) {
+		if (ovl_is_private_xattr(name))
+			continue;
 retry:
 		size = vfs_getxattr(old, name, value, value_size);
 		if (size == -ERANGE)
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 97fd65700ae2..69d715122598 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -221,8 +221,7 @@ static int ovl_readlink(struct dentry *dentry, char __user *buf, int bufsiz)
 	return realinode->i_op->readlink(realpath.dentry, buf, bufsiz);
 }
 
-
-static bool ovl_is_private_xattr(const char *name)
+bool ovl_is_private_xattr(const char *name)
 {
 	return strncmp(name, OVL_XATTR_PRE_NAME, OVL_XATTR_PRE_LEN) == 0;
 }
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 983540910ba8..32b077b07085 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -174,6 +174,7 @@ ssize_t ovl_getxattr(struct dentry *dentry, const char *name,
 ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size);
 int ovl_removexattr(struct dentry *dentry, const char *name);
 struct inode *ovl_d_select_inode(struct dentry *dentry, unsigned file_flags);
+bool ovl_is_private_xattr(const char *name);
 
 struct inode *ovl_new_inode(struct super_block *sb, umode_t mode,
 			    struct ovl_entry *oe);