net/smc: Stop the CLC flow if no link to map buffers on

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@linux.alibaba.com>
Link: https://lore.kernel.org/r/1663656189-32090-1-git-send-email-guwen@linux.alibaba.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c
index ebf56cdf17dbbb5d0e0df48f96757e42e269cf74..df89c2e08cbf455de32166df8d9854a94ae5f64f 100644 (file)
--- 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;
 }