Re: [PATCH] RDMA/siw: Clear association under lock if siw_qp_modify fails in siw_accept

[Bernard Metzler <bernard.metzler@linux.dev>]

On 25.08.2026 15:09, Guoqing Jiang wrote:
> We need to clear qp and cep before release state_lock as siw_qp_llp_closeo
> and siw_qp_modify->siw_qp_llp_close did.
> 
> Otherwise if siw_qp_modify() fails in siw_accept(), the QP's state_lock
> is released before the error path cleanup. A concurrent ibv_modify_qp()
> transitioning the QP to ERROR can race in this window:
> 
>    siw_accept()                       ibv_modify_qp(ERROR)
>    ----------------------             ----------------------
>    siw_qp_modify() fails
>    up_write(&qp->state_lock)
>                                       down_write(&qp->state_lock)
>                                       nextstate_from_idle():
> 				     if (qp->cep)
>                                         siw_cep_put(qp->cep) <- frees cep
>                                         qp->cep = NULL
>    goto error
>      cep->qp = NULL                   <- UAF
> 
> Clear qp->cep and cep->qp, and drop the association reference taken by
> siw_cep_get(), all under the write lock held from the initial
> down_write(&qp->state_lock). Thread B therefore sees qp->cep == NULL,
> skips its own put, and cannot free the cep before siw_accept() is done
> with it.
> 
> Reported-by: Shuangpeng Bai <shuangpeng.kernel@gmail.com>
> Link: https://lore.kernel.org/linux-rdma/d6fbe475-a5c2-f975-99b0-a0bd6b6d10e8@linux.dev/T/#m5876c1ff2de8686a9a1173b8f1aa0ff5363a785c
> Signed-off-by: Guoqing Jiang <guoqing.jiang@linux.dev>
> ---
>   drivers/infiniband/sw/siw/siw_cm.c | 8 ++++++--
>   1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/infiniband/sw/siw/siw_cm.c b/drivers/infiniband/sw/siw/siw_cm.c
> index 0245b25e7271..1573f2e888b2 100644
> --- a/drivers/infiniband/sw/siw/siw_cm.c
> +++ b/drivers/infiniband/sw/siw/siw_cm.c
> @@ -1719,9 +1719,13 @@ int siw_accept(struct iw_cm_id *id, struct iw_cm_conn_param *params)
>   			   SIW_QP_ATTR_STATE | SIW_QP_ATTR_LLP_HANDLE |
>   				   SIW_QP_ATTR_ORD | SIW_QP_ATTR_IRD |
>   				   SIW_QP_ATTR_MPA);
> +	if (rv) {
> +		cep->qp = NULL;
This can better be omitted since done in error_unlock path
anyway and is redundant otherwise. It would also better
retain the logic of calling siw_qp_put(qp) right after
clearing cep's reference to the qp, as done in error path.

Thank you!
Bernard.> +		qp->cep = NULL;
> +		siw_cep_put(cep);
> +		goto error_unlock;
> +	}
>   	up_write(&qp->state_lock);
> -	if (rv)
> -		goto error;
>   
>   	siw_dbg_cep(cep, "[QP %u]: send mpa reply, %d byte pdata\n",
>   		    qp_id(qp), params->private_data_len);