Re: [PATCH] ksmbd: fix leak of transform buffer on encrypt_resp() failure

[Namjae Jeon <linkinjeon@kernel.org>]

On Tue, Nov 4, 2025 at 11:12 PM Qianchang Zhao <pioooooooooip@gmail.com> wrote:
>
> When encrypt_resp() fails at the send path, we only set
> STATUS_DATA_ERROR but leave the transform buffer allocated (work->tr_buf
> in this tree). Repeating this path leaks kernel memory and can lead to
> OOM (DoS) when encryption is required.
>
> Reproduced on: Linux v6.18-rc2 (self-built test kernel)
>
> Fix by freeing the transform buffer and forcing plaintext error reply.
>
> Reported-by: Qianchang Zhao <pioooooooooip@gmail.com>
> Reported-by: Zhitong Liu <liuzhitong1993@gmail.com>
> Cc: stable@vger.kernel.org
> Signed-off-by: Qianchang Zhao <pioooooooooip@gmail.com>
> ---
>  fs/smb/server/server.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/fs/smb/server/server.c b/fs/smb/server/server.c
> index 40420544c..15dd13e76 100644
> --- a/fs/smb/server/server.c
> +++ b/fs/smb/server/server.c
> @@ -244,8 +244,14 @@ static void __handle_ksmbd_work(struct ksmbd_work *work,
>         if (work->sess && work->sess->enc && work->encrypted &&
>             conn->ops->encrypt_resp) {
>                 rc = conn->ops->encrypt_resp(work);
> -               if (rc < 0)
> +               if (rc < 0) {
>                         conn->ops->set_rsp_status(work, STATUS_DATA_ERROR);
> +                       work->encrypted = false;
> +                       if (work->tr_buf) {
> +                               kvfree(work->tr_buf);
->tr_buf is freed in ksmbd_free_work_struct(). How can tr_buf not be freed?
Thanks.
> +                               work->tr_buf = NULL;
> +                       }
> +               }
>         }
>         if (work->sess)
>                 ksmbd_user_session_put(work->sess);
> --
> 2.34.1
>