CVE-2023-53110: NULL Pointer Dereference

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

net/smc: fix NULL sndbuf_desc in smc_cdc_tx_handler()

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 smc_smcr_terminate_all() and smc_buf_create().

smc_smcr_terminate_all

smc_buf_create /* 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.