[PATCH 5.15 111/148] net/smc: Stop the CLC flow if no link to map buffers on

[Greg Kroah-Hartman]

From: Wen Gu <guwen@xxxxxxxxxxxxxxxxx>

[ Upstream commit e738455b2c6dcdab03e45d97de36476f93f557d2 ]

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>
Link: https://lore.kernel.org/r/1663656189-32090-1-git-send-email-guwen@xxxxxxxxxxxxxxxxx
Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 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 7401ec67ebcf..2eafefa15a1a 100644
--- a/net/smc/smc_core.c
+++ b/net/smc/smc_core.c
@@ -1980,7 +1980,7 @@ 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);
@@ -1993,9 +1993,12 @@ 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;
 }
 
-- 
2.35.1