net/smc: fix NULL sndbuf_desc in smc_cdc_tx_handler()

Vulnerability Description

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.

References

• https://git.kernel.org/stable/c/31817c530768b0199771ec6019571b4f0ddbf230
• https://git.kernel.org/stable/c/b108bd9e6be000492ebebe867daa699285978a10
• https://git.kernel.org/stable/c/3c270435db8aa34929263dddae8fd050f5216ecb
• https://git.kernel.org/stable/c/3ebac7cf0a184a8102821a7a00203f02bebda83c
• https://git.kernel.org/stable/c/22a825c541d775c1dbe7b2402786025acad6727b