Re: [PATCH] RDMA/rxe: Fix configuration of atomic queue pair attributes

[Zhu Yanjun <zyjzyj2000@gmail.com>]

Sorry, when max_rd_atomic will be set to 0?

Thanks,
Zhu Yanjun

On Tue, Feb 18, 2020 at 4:59 AM Bart Van Assche <bvanassche@acm.org> wrote:
>
> From the comment above the definition of the roundup_pow_of_two() macro:
>
>      The result is undefined when n == 0.
>
> Hence only pass positive values to roundup_pow_of_two(). This patch fixes
> the following UBSAN complaint:
>
> UBSAN: Undefined behaviour in ./include/linux/log2.h:57:13
> shift exponent 64 is too large for 64-bit type 'long unsigned int'
> Call Trace:
>  dump_stack+0xa5/0xe6
>  ubsan_epilogue+0x9/0x26
>  __ubsan_handle_shift_out_of_bounds.cold+0x4c/0xf9
>  rxe_qp_from_attr.cold+0x37/0x5d [rdma_rxe]
>  rxe_modify_qp+0x59/0x70 [rdma_rxe]
>  _ib_modify_qp+0x5aa/0x7c0 [ib_core]
>  ib_modify_qp+0x3b/0x50 [ib_core]
>  cma_modify_qp_rtr+0x234/0x260 [rdma_cm]
>  __rdma_accept+0x1a7/0x650 [rdma_cm]
>  nvmet_rdma_cm_handler+0x1286/0x14cd [nvmet_rdma]
>  cma_cm_event_handler+0x6b/0x330 [rdma_cm]
>  cma_ib_req_handler+0xe60/0x22d0 [rdma_cm]
>  cm_process_work+0x30/0x140 [ib_cm]
>  cm_req_handler+0x11f4/0x1cd0 [ib_cm]
>  cm_work_handler+0xb8/0x344e [ib_cm]
>  process_one_work+0x569/0xb60
>  worker_thread+0x7a/0x5d0
>  kthread+0x1e6/0x210
>  ret_from_fork+0x24/0x30
>
> Cc: Moni Shoua <monis@mellanox.com>
> Fixes: 8700e3e7c485 ("Soft RoCE driver")
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
> ---
>  drivers/infiniband/sw/rxe/rxe_qp.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/infiniband/sw/rxe/rxe_qp.c b/drivers/infiniband/sw/rxe/rxe_qp.c
> index ec21f616ac98..6c11c3aeeca6 100644
> --- a/drivers/infiniband/sw/rxe/rxe_qp.c
> +++ b/drivers/infiniband/sw/rxe/rxe_qp.c
> @@ -590,15 +590,16 @@ int rxe_qp_from_attr(struct rxe_qp *qp, struct ib_qp_attr *attr, int mask,
>         int err;
>
>         if (mask & IB_QP_MAX_QP_RD_ATOMIC) {
> -               int max_rd_atomic = __roundup_pow_of_two(attr->max_rd_atomic);
> +               int max_rd_atomic = attr->max_rd_atomic ?
> +                       roundup_pow_of_two(attr->max_rd_atomic) : 0;
>
>                 qp->attr.max_rd_atomic = max_rd_atomic;
>                 atomic_set(&qp->req.rd_atomic, max_rd_atomic);
>         }
>
>         if (mask & IB_QP_MAX_DEST_RD_ATOMIC) {
> -               int max_dest_rd_atomic =
> -                       __roundup_pow_of_two(attr->max_dest_rd_atomic);
> +               int max_dest_rd_atomic = attr->max_dest_rd_atomic ?
> +                       roundup_pow_of_two(attr->max_dest_rd_atomic) : 0;
>
>                 qp->attr.max_dest_rd_atomic = max_dest_rd_atomic;
>