On Tue, Aug 11, 2020 at 2:15 PM Leon Romanovsky <leon@xxxxxxxxxx> wrote:
>
> On Mon, Aug 10, 2020 at 05:20:49PM +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 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);
> > + }
>
> I afraid that you overcomplicated here, ib_register_client() doesn't
> return error if ->add() for specific device failed, it doesn't mean
> that ->add won't be called again for another device.
>
> So you don't need to use ib_dev_count == -1, just keep it to be 0 and
> leave to rtrs_srv_close() to free srv_ctx.
Leaving it 0 when there is an error is not gonna work. Since when the
modules are all built-in, a call to ib_register_client() will not
result in a call to ->add() then and there. So ib_register_client()
will return after registering the client, but without calling ->add().
Which means, ib_dev_count would be 0.
>
> Failure to call ->add shouldn't be any different from no-ib-devices situation.
>
> Thanks
>
> > +
> > 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
> >
--
Regards
-Haris
