[PATCH 5.4 05/47] ubifs: prevent creating duplicate encrypted filenames

[Greg Kroah-Hartman]

From: Eric Biggers <ebigg...@google.com>

commit 76786a0f083473de31678bdb259a3d4167cf756d upstream.

As described in "fscrypt: add fscrypt_is_nokey_name()", it's possible to
create a duplicate filename in an encrypted directory by creating a file
concurrently with adding the directory's encryption key.

Fix this bug on ubifs by rejecting no-key dentries in ubifs_create(),
ubifs_mkdir(), ubifs_mknod(), and ubifs_symlink().

Note that ubifs doesn't actually report the duplicate filenames from
readdir, but rather it seems to replace the original dentry with a new
one (which is still wrong, just a different effect from ext4).

On ubifs, this fixes xfstest generic/595 as well as the new xfstest I
wrote specifically for this bug.

Fixes: f4f61d2cc6d8 ("ubifs: Implement encrypted filenames")
Cc: sta...@vger.kernel.org
Link: https://lore.kernel.org/r/20201118075609.120337-5-ebigg...@kernel.org
Signed-off-by: Eric Biggers <ebigg...@google.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 fs/ubifs/dir.c |   17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

--- a/fs/ubifs/dir.c
+++ b/fs/ubifs/dir.c
@@ -278,6 +278,15 @@ done:
        return d_splice_alias(inode, dentry);
 }
 
+static int ubifs_prepare_create(struct inode *dir, struct dentry *dentry,
+                               struct fscrypt_name *nm)
+{
+       if (fscrypt_is_nokey_name(dentry))
+               return -ENOKEY;
+
+       return fscrypt_setup_filename(dir, &dentry->d_name, 0, nm);
+}
+
 static int ubifs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
                        bool excl)
 {
@@ -301,7 +310,7 @@ static int ubifs_create(struct inode *di
        if (err)
                return err;
 
-       err = fscrypt_setup_filename(dir, &dentry->d_name, 0, &nm);
+       err = ubifs_prepare_create(dir, dentry, &nm);
        if (err)
                goto out_budg;
 
@@ -961,7 +970,7 @@ static int ubifs_mkdir(struct inode *dir
        if (err)
                return err;
 
-       err = fscrypt_setup_filename(dir, &dentry->d_name, 0, &nm);
+       err = ubifs_prepare_create(dir, dentry, &nm);
        if (err)
                goto out_budg;
 
@@ -1046,7 +1055,7 @@ static int ubifs_mknod(struct inode *dir
                return err;
        }
 
-       err = fscrypt_setup_filename(dir, &dentry->d_name, 0, &nm);
+       err = ubifs_prepare_create(dir, dentry, &nm);
        if (err) {
                kfree(dev);
                goto out_budg;
@@ -1130,7 +1139,7 @@ static int ubifs_symlink(struct inode *d
        if (err)
                return err;
 
-       err = fscrypt_setup_filename(dir, &dentry->d_name, 0, &nm);
+       err = ubifs_prepare_create(dir, dentry, &nm);
        if (err)
                goto out_budg;