[PATCH net] net/smc: fix NULL sndbuf_desc in smc_cdc_tx_handler()

[PATCH net] net/smc: fix NULL sndbuf_desc in smc_cdc_tx_handler()

[D. Wythe]

From: "D. Wythe" <alibuda@linux.alibaba.com>

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@linux.alibaba.com>
---
 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;
+
 	smc_cdc_add_pending_send(conn, pend);
 
 	conn->tx_cdc_seq++;
-- 
1.8.3.1

Re: [PATCH net] net/smc: fix NULL sndbuf_desc in smc_cdc_tx_handler()

[Tony Lu]

On Mon, Mar 06, 2023 at 11:36:26AM +0800, D. Wythe wrote:
> From: "D. Wythe" <alibuda@linux.alibaba.com>
> 
> 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@linux.alibaba.com>

LGTM.

Reviewed-by: Tony Lu <tonylu@linux.alibaba.com>

> ---
>  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;
> +
>  	smc_cdc_add_pending_send(conn, pend);
>  
>  	conn->tx_cdc_seq++;
> -- 
> 1.8.3.1

Re: [PATCH net] net/smc: fix NULL sndbuf_desc in smc_cdc_tx_handler()

[Alexander H Duyck]

On Mon, 2023-03-06 at 11:36 +0800, D. Wythe wrote:
> From: "D. Wythe" <alibuda@linux.alibaba.com>
> 
> 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@linux.alibaba.com>

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.

> ---
>  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?

>  	smc_cdc_add_pending_send(conn, pend);
>  
>  	conn->tx_cdc_seq++;

Re: [PATCH net] net/smc: fix NULL sndbuf_desc in smc_cdc_tx_handler()

[Wenjia Zhang]

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@linux.alibaba.com>
>>
>> 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@linux.alibaba.com>
> 
> 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++;
> 
> 

Re: [PATCH net] net/smc: fix NULL sndbuf_desc in smc_cdc_tx_handler()

[Alexander H Duyck]

On Mon, 2023-03-06 at 22:06 +0100, Wenjia Zhang wrote:
> 
> 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@linux.alibaba.com>
> > > 
> > > 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@linux.alibaba.com>
> > 
> > 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.

Ah, okay that is what I was missing.

Re: [PATCH net] net/smc: fix NULL sndbuf_desc in smc_cdc_tx_handler()

[Tony Lu]

On Mon, Mar 06, 2023 at 08:38:52AM -0800, Alexander H Duyck wrote:
> On Mon, 2023-03-06 at 11:36 +0800, D. Wythe wrote:
> > From: "D. Wythe" <alibuda@linux.alibaba.com>
> > 
> > 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@linux.alibaba.com>
> 
> 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.
> 
> > ---
> >  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 with you. It is reasonable to use ENOBUFS here.

Thanks.

> >  	smc_cdc_add_pending_send(conn, pend);
> >  
> >  	conn->tx_cdc_seq++;
>