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    Subject[PATCH 4.19 05/35] ubifs: prevent creating duplicate encrypted filenames
    Date
    From: Eric Biggers <ebiggers@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: stable@vger.kernel.org
    Link: https://lore.kernel.org/r/20201118075609.120337-5-ebiggers@kernel.org
    Signed-off-by: Eric Biggers <ebiggers@google.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    fs/ubifs/dir.c | 17 +++++++++++++----
    1 file changed, 13 insertions(+), 4 deletions(-)

    --- a/fs/ubifs/dir.c
    +++ b/fs/ubifs/dir.c
    @@ -290,6 +290,15 @@ 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)
    {
    @@ -313,7 +322,7 @@ 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;

    @@ -977,7 +986,7 @@ 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;

    @@ -1062,7 +1071,7 @@ 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;
    @@ -1146,7 +1155,7 @@ 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;


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