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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Wen Gu <guwen@linux.alibaba.com>,
        Paolo Abeni <pabeni@redhat.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.19 152/207] net/smc: Stop the CLC flow if no link to map buffers on
Date:   Mon, 26 Sep 2022 12:12:21 +0200
Message-Id: <20220926100813.457204333@linuxfoundation.org>
In-Reply-To: <20220926100806.522017616@linuxfoundation.org>
References: <20220926100806.522017616@linuxfoundation.org>
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From: Wen Gu <guwen@linux.alibaba.com>

[ 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@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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 1f3bb1f6b1f7..8095876b66eb 100644
--- a/net/smc/smc_core.c
+++ b/net/smc/smc_core.c
@@ -2148,7 +2148,7 @@ 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);
@@ -2161,9 +2161,12 @@ 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