On Tue, Aug 11, 2020 at 12:53 PM Haris Iqbal
<haris.iqbal@xxxxxxxxxxxxxxx> wrote:
>
> On Tue, Aug 11, 2020 at 4:17 PM Leon Romanovsky <leon@xxxxxxxxxx> wrote:
> >
> > On Tue, Aug 11, 2020 at 02:27:12PM +0530, Haris Iqbal wrote:
> > > 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.
> >
> > If ib_dev_count == 0 => rtrs_srv_rdma_init() didn't success => nothing
> > to release.
>
> True, but we have to send a failure back to the caller of
> "rtrs_srv_open()" (and user of this ulp); which in our case is
> rnbd-srv's function rnbd_srv_init_module().
> In our case, the rnbd-drv module init would fail if "rtrs_srv_open()"
> fails, meaning rtrs_srv_rdma_init() had failed.
>
> Even if we are talking in generic terms, any module calling the
> "rtrs_srv_open()" of the rtrs ulp, would want to know if the server
> open failed or succeeded right?
I think Leon is right, any success of call to ->add, we have something
to rtrs_srv_rdma_init,
we can consider rtrs_srv_open is success instead of an error.
Thanks Leon for catching this.
Regards!
