fs, fscrypt: clear DCACHE_ENCRYPTED_NAME when unaliasing directory

Make __d_move() clear DCACHE_ENCRYPTED_NAME on the source dentry.  This
is needed for when d_splice_alias() moves a directory's encrypted alias
to its decrypted alias as a result of the encryption key being added.

Otherwise, the decrypted alias will incorrectly be invalidated on the
next lookup, causing problems such as unmounting a mount the user just
mount()ed there.

Note that we don't have to support arbitrary moves of this flag because
fscrypt doesn't allow dentries with DCACHE_ENCRYPTED_NAME to be the
source or target of a rename().

Fixes: 28b4c263961c ("ext4 crypto: revalidate dentry after adding or removing the key")
Reported-by: Sarthak Kukreti <sarthakkukreti@chromium.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index aac41adf4743..647e6ed426e2 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -18,6 +18,7 @@
 #include <linux/string.h>
 #include <linux/mm.h>
 #include <linux/fs.h>
+#include <linux/fscrypt.h>
 #include <linux/fsnotify.h>
 #include <linux/slab.h>
 #include <linux/init.h>
@@ -2795,6 +2796,7 @@ static void __d_move(struct dentry *dentry, struct dentry *target,
         list_move(&dentry->d_child, &dentry->d_parent->d_subdirs);
         __d_rehash(dentry);
         fsnotify_update_flags(dentry);
+        fscrypt_handle_d_move(dentry);
 
         write_seqcount_end(&target->d_seq);
         write_seqcount_end(&dentry->d_seq);