On 06.03.23 17:38, Alexander H Duyck wrote:
On Mon, 2023-03-06 at 11:36 +0800, D. Wythe wrote:
From: "D. Wythe" <alibuda@xxxxxxxxxxxxxxxxx>
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.
Fixes: 0b29ec643613 ("net/smc: immediate termination for SMCR link groups")
Signed-off-by: D. Wythe <alibuda@xxxxxxxxxxxxxxxxx>
Looking at the code for __smc_buf_create it seems like you might have
more issues hiding in the code. From what I can tell smc_buf_get_slot
can only return a pointer or NULL but it is getting checked for being
being a PTR_ERR or IS_ERR in several spots that are likely all dead
code.
This smc_buf_get_slot() is used to get a reusable slot, which is
originally assigned by smcr_new_buf_create() or smcd_new_buf_create()
depending on the device being used. In
smcr_new_buf_create()/smcd_new_buf_create(), the pointer values of the
return codes are converted from integer values.
---
net/smc/smc_cdc.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/net/smc/smc_cdc.c b/net/smc/smc_cdc.c
index 53f63bf..2f0e2ee 100644
--- a/net/smc/smc_cdc.c
+++ b/net/smc/smc_cdc.c
@@ -114,6 +114,9 @@ int smc_cdc_msg_send(struct smc_connection *conn,
union smc_host_cursor cfed;
int rc;
+ if (unlikely(!READ_ONCE(conn->sndbuf_desc)))
+ return -EINVAL;
+
This return value doesn't seem right to me. Rather than en EINVAL
should this be something like a ENOBUFS just to make it easier to debug
when this issue is encountered?
I agree.
smc_cdc_add_pending_send(conn, pend);
conn->tx_cdc_seq++;
