CVE-2023-53110

In the Linux kernel, the following vulnerability has been resolved:

net/smc: fix NULL sndbufdesc in smccdctxhandler()

When performing a stress test on SMC-R by rmmod mlx5_ib driver during the wrk/nginx test, we found that there is a probability of triggering a panic while terminating all link groups.

This issue dues to the race between smcsmcrterminateall() and smcbuf_create().

        smc_smcr_terminate_all

smcbufcreate /* init */ conn->sndbuf_desc = NULL; ...

        __smc_lgr_terminate
            smc_conn_kill
                smc_close_abort
                    smc_cdc_get_slot_and_msg_send

        __softirqentry_text_start
            smc_wr_tx_process_cqe
                smc_cdc_tx_handler
                    READ(conn->sndbuf_desc->len);
                    /* panic dues to NULL sndbuf_desc */

conn->sndbuf_desc = xxx;

This patch tries to fix the issue by always to check the sndbuf_desc before send any cdc msg, to make sure that no null pointer is seen during cqe processing.