[PATCH] nvmet: nul-terminate the NQNs passed in the connect command

[Caleb Sander]

Won't this overrun the subsysnqn and hostnqn fields? Writing to
subsysnqn[NVMF_NQN_FIELD_LEN] will clobber the first char of hostnqn:
struct nvmf_connect_data {
        uuid_t hostid;
        __le16 cntlid;
        char resv4[238];
        char subsysnqn[NVMF_NQN_FIELD_LEN];
        char hostnqn[NVMF_NQN_FIELD_LEN];
        char resv5[256];
};

I think clearing the previous byte (index NVMF_NQN_FIELD_LEN - 1)
would work. The spec requires NQNs to be under 223 bytes anyways, so
they should never take up the whole field.

On Thu, Nov 9, 2023 at 10:45 PM Christoph Hellwig <hch at lst.de> wrote:
>
> The host and subsystem NQNs are passed in the connect command payload and
> interpreted as nul-terminated strings.  Ensure they actually are
> nul-terminated before using them.
>
> Fixes: a07b4970f464 "nvmet: add a generic NVMe target")
> Reported-by: Alon Zahavi <zahavi.alon at gmail.com>
> Signed-off-by: Christoph Hellwig <hch at lst.de>
> ---
>  drivers/nvme/target/fabrics-cmd.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/drivers/nvme/target/fabrics-cmd.c b/drivers/nvme/target/fabrics-cmd.c
> index 43b5bd8bb6a52d..0920fe7ce4ac99 100644
> --- a/drivers/nvme/target/fabrics-cmd.c
> +++ b/drivers/nvme/target/fabrics-cmd.c
> @@ -244,6 +244,8 @@ static void nvmet_execute_admin_connect(struct nvmet_req *req)
>                 goto out;
>         }
>
> +       d->subsysnqn[NVMF_NQN_FIELD_LEN] = '\0';
> +       d->hostnqn[NVMF_NQN_FIELD_LEN] = '\0';
>         status = nvmet_alloc_ctrl(d->subsysnqn, d->hostnqn, req,
>                                   le32_to_cpu(c->kato), &ctrl);
>         if (status)
> @@ -313,6 +315,8 @@ static void nvmet_execute_io_connect(struct nvmet_req *req)
>                 goto out;
>         }
>
> +       d->subsysnqn[NVMF_NQN_FIELD_LEN] = '\0';
> +       d->hostnqn[NVMF_NQN_FIELD_LEN] = '\0';
>         ctrl = nvmet_ctrl_find_get(d->subsysnqn, d->hostnqn,
>                                    le16_to_cpu(d->cntlid), req);
>         if (!ctrl) {
> --
> 2.39.2
>
>