Re: [PATCH v4] RDMA/rtrs-srv: Incorporate ib_register_client into rtrs server init

[Jason Gunthorpe <jgg@nvidia.com>]

On Mon, Sep 07, 2020 at 04:01:06PM +0530, Md Haris Iqbal wrote:
> The rnbd_server module's communication manager (cm) initialization depends
> on the registration of the "network namespace subsystem" of the RDMA CM
> agent module. As such, when the kernel is configured to load the
> rnbd_server and the RDMA cma module during initialization; and if the
> rnbd_server module is initialized before RDMA cma module, a null ptr
> dereference occurs during the RDMA bind operation.
> 
> Call trace below,
> 
> [    1.904782] Call Trace:
> [    1.904782]  ? xas_load+0xd/0x80
> [    1.904782]  xa_load+0x47/0x80
> [    1.904782]  cma_ps_find+0x44/0x70
> [    1.904782]  rdma_bind_addr+0x782/0x8b0
> [    1.904782]  ? get_random_bytes+0x35/0x40
> [    1.904782]  rtrs_srv_cm_init+0x50/0x80
> [    1.904782]  rtrs_srv_open+0x102/0x180
> [    1.904782]  ? rnbd_client_init+0x6e/0x6e
> [    1.904782]  rnbd_srv_init_module+0x34/0x84
> [    1.904782]  ? rnbd_client_init+0x6e/0x6e
> [    1.904782]  do_one_initcall+0x4a/0x200
> [    1.904782]  kernel_init_freeable+0x1f1/0x26e
> [    1.904782]  ? rest_init+0xb0/0xb0
> [    1.904782]  kernel_init+0xe/0x100
> [    1.904782]  ret_from_fork+0x22/0x30
> [    1.904782] Modules linked in:
> [    1.904782] CR2: 0000000000000015
> [    1.904782] ---[ end trace c42df88d6c7b0a48 ]---
> 
> All this happens cause the cm init is in the call chain of the module init,
> which is not a preferred practice.
> 
> So remove the call to rdma_create_id() from the module init call chain.
> Instead register rtrs-srv as an ib client, which makes sure that the
> rdma_create_id() is called only when an ib device is added.
> 
> Fixes: 9cb837480424 ("RDMA/rtrs: server: main functionality")
> Reported-by: kernel test robot <rong.a.chen@intel.com>
> Signed-off-by: Md Haris Iqbal <haris.iqbal@cloud.ionos.com>
> Reviewed-by: Jack Wang <jinpu.wang@cloud.ionos.com>
> Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
> ---
> Change in v4:
> 	Add mutex lock to prevent the add/remove of ib device from racing
> Change in v3:
> 	Remove RDMA init error check while rtrs server open
> 	Remove -1 assignment for ib_dev_count on RDMA init error
> Change in v2:
>         Use only single variable to track number of IB devices and failure
>         Change according to kernel coding style
> 
>  drivers/infiniband/ulp/rtrs/rtrs-srv.c | 77 +++++++++++++++++++++++++-
>  drivers/infiniband/ulp/rtrs/rtrs-srv.h |  7 +++
>  2 files changed, 81 insertions(+), 3 deletions(-)

Applied to for-next with Leon's remark

Thanks,
Jason