Re: [RFC PATCH] rpmsg: glink: Add bounds check on tx path

[Deepak Kumar Singh]

On 1/13/2024 5:55 AM, Michal Koutný wrote:
> Add bounds check on values read from shared memory in the tx path. In
> cases where the VM is misbehaving, the transport should exit and print a
> warning when bogus values may cause out of bounds to be read.
>
> Link: https://git.codelinaro.org/clo/la/kernel/msm-5.10/-/commit/32d9c3a2f2b6a4d1fc48d6871194f3faf3184e8b
> Suggested-by: Chris Lew <quic_clew@xxxxxxxxxxx>
> Suggested-by: Sarannya S <quic_sarannya@xxxxxxxxxxx>
> Signed-off-by: Michal Koutný <mkoutny@xxxxxxxx>
> ---
>   drivers/rpmsg/qcom_glink_smem.c | 9 +++++++++
>   1 file changed, 9 insertions(+)
>
> Why RFC? The patch is adopted from the link above. It would be good to
> asses whether such conditions can also happen with rpmsg glink.
> (And if so, whether the zeroed values are the best correction.)
Hi Michal,

There is already a patch posted for similar problem -
https://lore.kernel.org/all/20231201110631.669085-1-quic_deesin@xxxxxxxxxxx/

> diff --git a/drivers/rpmsg/qcom_glink_smem.c b/drivers/rpmsg/qcom_glink_smem.c
> index 7a982c60a8dd..3e786e590c03 100644
> --- a/drivers/rpmsg/qcom_glink_smem.c
> +++ b/drivers/rpmsg/qcom_glink_smem.c
> @@ -146,6 +146,11 @@ static size_t glink_smem_tx_avail(struct qcom_glink_pipe *np)
>   	else
>   		avail -= FIFO_FULL_RESERVE + TX_BLOCKED_CMD_RESERVE;
>   
> +	if (avail > pipe->native.length) {
> +		pr_warn_once("%s: avail clamped\n", __func__);
> +		avail = 0;
> +	}
> +
>   	return avail;
>   }
>   
> @@ -177,6 +182,10 @@ static void glink_smem_tx_write(struct qcom_glink_pipe *glink_pipe,
>   	unsigned int head;
>   
>   	head = le32_to_cpu(*pipe->head);
> +	if (head > pipe->native.length) {
> +		pr_warn_once("%s: head overflow\n", __func__);
> +		return;
> +	}
>   
>   	head = glink_smem_tx_write_one(pipe, head, hdr, hlen);
>   	head = glink_smem_tx_write_one(pipe, head, data, dlen);