Hi Leon,
On Thu, Aug 20, 2020 at 9:26 AM Leon Romanovsky <leon@xxxxxxxxxx> wrote:
>
> On Thu, Aug 20, 2020 at 09:11:52AM +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@xxxxxxxxx>
> > Signed-off-by: Md Haris Iqbal <haris.iqbal@xxxxxxxxxxxxxxx>
> > ---
> > Change in v3:
> > Removed RDMA init error check while rtrs server open
> > Removed -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 | 69 ++++++++++++++++++++++++--
> > drivers/infiniband/ulp/rtrs/rtrs-srv.h | 6 +++
> > 2 files changed, 72 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/infiniband/ulp/rtrs/rtrs-srv.c b/drivers/infiniband/ulp/rtrs/rtrs-srv.c
> > index a219bd1bdbc2..febc1478b96f 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 +2035,63 @@ 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");
> > + 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
> > @@ -2051,7 +2110,12 @@ 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,
> > + };
>
> It can be my personal issue, but I prefer to see this type of assignment in variable declarations only.
> In the code, the better style will be to use direct assignment, e.g. "ib.ctx.port = port;"
> It will simplify future refactoring.
>
> Thanks
Thanks for your suggestion, but we have a few other place using the
same style, eg
https://elixir.bootlin.com/linux/latest/source/drivers/infiniband/ulp/rtrs/rtrs-srv.c#L1545
It's more consistent to keep it as it is, IMO.
Regards!
