Re: [PATCH net] net/smc: Stop the CLC flow if no link to map buffers on

[Wenjia Zhang]

On 22.09.22 10:29, Wen Gu wrote:
> On 2022/9/20 14:43, Wen Gu wrote:
>
> > There might be a potential race between SMC-R buffer map and
> > link group termination.
> >
> > smc_smcr_terminate_all()     | smc_connect_rdma()
> > --------------------------------------------------------------
> >                               | smc_conn_create()
> > for links in smcibdev        |
> >          schedule links down  |
> >                               | smc_buf_create()
> >                               |  \- smcr_buf_map_usable_links()
> >                               |      \- no usable links found,
> >                               |         (rmb->mr = NULL)
> >                               |
> >                               | smc_clc_send_confirm()
> >                               |  \- access conn->rmb_desc->mr[]->rkey
> >                               |     (panic)
> >
> > During reboot and IB device module remove, all links will be set
> > down and no usable links remain in link groups. In such situation
> > smcr_buf_map_usable_links() should return an error and stop the
> > CLC flow accessing to uninitialized mr.
> >
> > Fixes: b9247544c1bc ("net/smc: convert static link ID instances to 
> > support multiple links")
> > Signed-off-by: Wen Gu <guwen@xxxxxxxxxxxxxxxxx>
> > ---
> >   net/smc/smc_core.c | 5 ++++-
> >   1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c
> > index ebf56cd..df89c2e 100644
> > --- a/net/smc/smc_core.c
> > +++ b/net/smc/smc_core.c
> > @@ -2239,7 +2239,7 @@ static struct smc_buf_desc 
> > *smcr_new_buf_create(struct smc_link_group *lgr,
> >   static int smcr_buf_map_usable_links(struct smc_link_group *lgr,
> >                        struct smc_buf_desc *buf_desc, bool is_rmb)
> >   {
> > -    int i, rc = 0;
> > +    int i, rc = 0, cnt = 0;
> >       /* protect against parallel link reconfiguration */
> >       mutex_lock(&lgr->llc_conf_mutex);
> > @@ -2252,9 +2252,12 @@ static int smcr_buf_map_usable_links(struct 
> > smc_link_group *lgr,
> >               rc = -ENOMEM;
> >               goto out;
> >           }
> > +        cnt++;
> >       }
> >   out:
> >       mutex_unlock(&lgr->llc_conf_mutex);
> > +    if (!rc && !cnt)
> > +        rc = -EINVAL;
> >       return rc;
> >   }
>
> Any comments or reviews are welcome and appreciated.
>
> Thanks,
> Wen Gu

Sorry for the late answer!
Good catch! Thank you!

Acked-by: Wenjia Zhang <wenjia@xxxxxxxxxxxxx>