On Mon, Aug 10, 2020 at 1:51 PM Md Haris Iqbal
<haris.iqbal@xxxxxxxxxxxxxxx> 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@xxxxxxxxx>
> Signed-off-by: Md Haris Iqbal <haris.iqbal@xxxxxxxxxxxxxxx>
> ---
> 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 | 79 +++++++++++++++++++++++++-
> drivers/infiniband/ulp/rtrs/rtrs-srv.h | 6 ++
> 2 files changed, 82 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/infiniband/ulp/rtrs/rtrs-srv.c b/drivers/infiniband/ulp/rtrs/rtrs-srv.c
> index 0d9241f5d9e6..69a37ce73b0c 100644
> --- a/drivers/infiniband/ulp/rtrs/rtrs-srv.c
> +++ b/drivers/infiniband/ulp/rtrs/rtrs-srv.c
> @@ -16,6 +16,7 @@
> #include "rtrs-srv.h"
> #include "rtrs-log.h"
> #include <rdma/ib_cm.h>
> +#include <rdma/ib_verbs.h>
>
> MODULE_DESCRIPTION("RDMA Transport Server");
> MODULE_LICENSE("GPL");
> @@ -31,6 +32,7 @@ MODULE_LICENSE("GPL");
> static struct rtrs_rdma_dev_pd dev_pd;
> static mempool_t *chunk_pool;
> struct class *rtrs_dev_class;
> +static struct rtrs_srv_ib_ctx ib_ctx;
>
> static int __read_mostly max_chunk_size = DEFAULT_MAX_CHUNK_SIZE;
> static int __read_mostly sess_queue_depth = DEFAULT_SESS_QUEUE_DEPTH;
> @@ -2033,6 +2035,64 @@ static void free_srv_ctx(struct rtrs_srv_ctx *ctx)
> kfree(ctx);
> }
>
> +static int rtrs_srv_add_one(struct ib_device *device)
> +{
> + struct rtrs_srv_ctx *ctx;
> + int ret;
> +
> + if (ib_ctx.ib_dev_count)
> + goto out;
> +
> + /*
> + * Since our CM IDs are NOT bound to any ib device we will create them
> + * only once
> + */
> + ctx = ib_ctx.srv_ctx;
> + ret = rtrs_srv_rdma_init(ctx, ib_ctx.port);
> + if (ret) {
> + /*
> + * We errored out here.
> + * According to the ib code, if we encounter an error here then the
> + * error code is ignored, and no more calls to our ops are made.
> + */
> + pr_err("Failed to initialize RDMA connection");
> + ib_ctx.ib_dev_count = -1;
> + return ret;
> + }
> +
> +out:
> + /*
> + * Keep a track on the number of ib devices added
> + */
> + ib_ctx.ib_dev_count++;
> +
> + return 0;
> +}
> +
> +static void rtrs_srv_remove_one(struct ib_device *device, void *client_data)
> +{
> + struct rtrs_srv_ctx *ctx;
> +
> + ib_ctx.ib_dev_count--;
> +
> + if (ib_ctx.ib_dev_count)
> + return;
> +
> + /*
> + * Since our CM IDs are NOT bound to any ib device we will remove them
> + * only once, when the last device is removed
> + */
> + ctx = ib_ctx.srv_ctx;
> + rdma_destroy_id(ctx->cm_id_ip);
> + rdma_destroy_id(ctx->cm_id_ib);
> +}
> +
> +static struct ib_client rtrs_srv_client = {
> + .name = "rtrs_server",
> + .add = rtrs_srv_add_one,
> + .remove = rtrs_srv_remove_one
> +};
> +
> /**
> * rtrs_srv_open() - open RTRS server context
> * @ops: callback functions
> @@ -2051,12 +2111,26 @@ struct rtrs_srv_ctx *rtrs_srv_open(struct rtrs_srv_ops *ops, u16 port)
> if (!ctx)
> return ERR_PTR(-ENOMEM);
>
> - err = rtrs_srv_rdma_init(ctx, port);
> + ib_ctx = (struct rtrs_srv_ib_ctx) {
> + .srv_ctx = ctx,
> + .port = port,
> + };
> +
> + err = ib_register_client(&rtrs_srv_client);
> if (err) {
> free_srv_ctx(ctx);
> return ERR_PTR(err);
> }
>
> + /*
> + * Since ib_register_client does not propagate the device add error
> + * we check if .add was called and the RDMA connection init failed
> + */
> + if (ib_ctx.ib_dev_count < 0) {
> + free_srv_ctx(ctx);
> + return ERR_PTR(-ENODEV);
> + }
> +
> return ctx;
> }
> EXPORT_SYMBOL(rtrs_srv_open);
> @@ -2090,8 +2164,7 @@ static void close_ctx(struct rtrs_srv_ctx *ctx)
> */
> void rtrs_srv_close(struct rtrs_srv_ctx *ctx)
> {
> - rdma_destroy_id(ctx->cm_id_ip);
> - rdma_destroy_id(ctx->cm_id_ib);
> + ib_unregister_client(&rtrs_srv_client);
> close_ctx(ctx);
> free_srv_ctx(ctx);
> }
> diff --git a/drivers/infiniband/ulp/rtrs/rtrs-srv.h b/drivers/infiniband/ulp/rtrs/rtrs-srv.h
> index dc95b0932f0d..e8f7e99a9a6e 100644
> --- a/drivers/infiniband/ulp/rtrs/rtrs-srv.h
> +++ b/drivers/infiniband/ulp/rtrs/rtrs-srv.h
> @@ -118,6 +118,12 @@ struct rtrs_srv_ctx {
> struct list_head srv_list;
> };
>
> +struct rtrs_srv_ib_ctx {
> + struct rtrs_srv_ctx *srv_ctx;
> + u16 port;
> + int ib_dev_count;
> +};
> +
> extern struct class *rtrs_dev_class;
>
> void close_sess(struct rtrs_srv_sess *sess);
> --
> 2.25.1
>
This patch goes all the way registering an ib client in order to call
rdma_bind_addr only after the first device is added instead of calling
it from module_init directly.
I think the original one line fix
https://www.spinics.net/lists/linux-rdma/msg93267.html was good enough
to close a bug triggered only when all modules are build-in.
Since the convention appears to be to call ib_client_register, this
also looks good to me.
Thanks you!
Acked-by: Danil Kipnis <danil.kipnis@xxxxxxxxxxxxxxx>
