Re: [PATCH v2] RDMA/srpt: Fix srpt_alloc_rw_ctxs() unwind counters

[Bart Van Assche <bvanassche@acm.org>]

On 7/15/26 3:15 AM, kensanya@163.com wrote:
> From: TanZheng <tanzheng@kylinos.cn>
> 
> When srpt_alloc_rw_ctxs() fails partway through a multi-buffer indirect
> descriptor, the unwind path destroys RDMA contexts but leaves stale
> n_rw_ctx and n_rdma values (and a dangling rw_ctxs pointer). Later
> sq_wr_avail accounting in srpt_queue_response() or srpt_write_pending()
> can then subtract the wrong number of send queue credits.
> 
> Reset the counters and clear rw_ctxs after freeing the heap
> allocation before returning an error.
> 
> Fixes: b99f8e4d7bcd ("IB/srpt: convert to the generic RDMA READ/WRITE API")
> Signed-off-by: TanZheng <tanzheng@kylinos.cn>
> ---
> v2:
> - After kfree(), set rw_ctxs to NULL instead of &s_rw_ctx
>    (Leon Romanovsky)
> 
>   drivers/infiniband/ulp/srpt/ib_srpt.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/infiniband/ulp/srpt/ib_srpt.c b/drivers/infiniband/ulp/srpt/ib_srpt.c
> index f66cfd70c263..a9c4995af7a3 100644
> --- a/drivers/infiniband/ulp/srpt/ib_srpt.c
> +++ b/drivers/infiniband/ulp/srpt/ib_srpt.c
> @@ -1014,8 +1014,12 @@ static int srpt_alloc_rw_ctxs(struct srpt_send_ioctx *ioctx,
>   				ctx->sg, ctx->nents, dir);
>   		target_free_sgl(ctx->sg, ctx->nents);
>   	}
> -	if (ioctx->rw_ctxs != &ioctx->s_rw_ctx)
> +	if (ioctx->rw_ctxs != &ioctx->s_rw_ctx) {
>   		kfree(ioctx->rw_ctxs);
> +		ioctx->rw_ctxs = NULL;
> +	}
> +	ioctx->n_rw_ctx = 0;
> +	ioctx->n_rdma = 0;
>   	return ret;
>   }

The above looks wrong to me. In the error path ioctx->n_rw_ctx should be
restored to the value it had at the start of the function instead of
resetting it to zero.

Bart.