[PATCH net] net/smc: fix application data exception

[PATCH net] net/smc: fix application data exception

[D.Wythe]

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

There is a certain probability that following
exceptions will occur in the wrk benchmark test:

Running 10s test @ http://11.213.45.6:80
  8 threads and 64 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency     3.72ms   13.94ms 245.33ms   94.17%
    Req/Sec     1.96k   713.67     5.41k    75.16%
  155262 requests in 10.10s, 23.10MB read
Non-2xx or 3xx responses: 3

We will find that the error is HTTP 400 error, which is a serious
exception in our test, which means the application data was
corrupted.

Consider the following scenarios:

CPU0                            CPU1

buf_desc->used = 0;
                                cmpxchg(buf_desc->used, 0, 1)
                                deal_with(buf_desc)

memset(buf_desc->cpu_addr,0);

This will cause the data received by a victim connection to be cleared,
thus triggering an HTTP 400 error in the server.

This patch exchange the order between clear used and memset, add
barrier to ensure memory consistency.

Fixes: 1c5526968e27 ("net/smc: Clear memory when release and reuse buffer")
Signed-off-by: D. Wythe <alibuda@linux.alibaba.com>
---
 net/smc/smc_core.c | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c
index c305d8d..c19d4b7 100644
--- a/net/smc/smc_core.c
+++ b/net/smc/smc_core.c
@@ -1120,8 +1120,9 @@ static void smcr_buf_unuse(struct smc_buf_desc *buf_desc, bool is_rmb,
 
 		smc_buf_free(lgr, is_rmb, buf_desc);
 	} else {
-		buf_desc->used = 0;
-		memset(buf_desc->cpu_addr, 0, buf_desc->len);
+		/* memzero_explicit provides potential memory barrier semantics */
+		memzero_explicit(buf_desc->cpu_addr, buf_desc->len);
+		WRITE_ONCE(buf_desc->used, 0);
 	}
 }
 
@@ -1132,19 +1133,17 @@ static void smc_buf_unuse(struct smc_connection *conn,
 		if (!lgr->is_smcd && conn->sndbuf_desc->is_vm) {
 			smcr_buf_unuse(conn->sndbuf_desc, false, lgr);
 		} else {
-			conn->sndbuf_desc->used = 0;
-			memset(conn->sndbuf_desc->cpu_addr, 0,
-			       conn->sndbuf_desc->len);
+			memzero_explicit(conn->sndbuf_desc->cpu_addr, conn->sndbuf_desc->len);
+			WRITE_ONCE(conn->sndbuf_desc->used, 0);
 		}
 	}
 	if (conn->rmb_desc) {
 		if (!lgr->is_smcd) {
 			smcr_buf_unuse(conn->rmb_desc, true, lgr);
 		} else {
-			conn->rmb_desc->used = 0;
-			memset(conn->rmb_desc->cpu_addr, 0,
-			       conn->rmb_desc->len +
-			       sizeof(struct smcd_cdc_msg));
+			memzero_explicit(conn->rmb_desc->cpu_addr,
+					 conn->rmb_desc->len + sizeof(struct smcd_cdc_msg));
+			WRITE_ONCE(conn->rmb_desc->used, 0);
 		}
 	}
 }
-- 
1.8.3.1

Re: [PATCH net] net/smc: fix application data exception

[D. Wythe]

Hi, wenjia

This patch of bugfix seems to have been hanging for a long time.
If you have any concerns, please let us know.

Best wishes.
D. Wythe


On 11/26/22 4:22 PM, D.Wythe wrote:
> From: "D. Wythe" <alibuda@linux.alibaba.com>
> 
> There is a certain probability that following
> exceptions will occur in the wrk benchmark test:
> 
> Running 10s test @ http://11.213.45.6:80
>    8 threads and 64 connections
>    Thread Stats   Avg      Stdev     Max   +/- Stdev
>      Latency     3.72ms   13.94ms 245.33ms   94.17%
>      Req/Sec     1.96k   713.67     5.41k    75.16%
>    155262 requests in 10.10s, 23.10MB read
> Non-2xx or 3xx responses: 3
> 
> We will find that the error is HTTP 400 error, which is a serious
> exception in our test, which means the application data was
> corrupted.
> 
> Consider the following scenarios:
> 
> CPU0                            CPU1
> 
> buf_desc->used = 0;
>                                  cmpxchg(buf_desc->used, 0, 1)
>                                  deal_with(buf_desc)
> 
> memset(buf_desc->cpu_addr,0);
> 
> This will cause the data received by a victim connection to be cleared,
> thus triggering an HTTP 400 error in the server.
> 
> This patch exchange the order between clear used and memset, add
> barrier to ensure memory consistency.
> 
> Fixes: 1c5526968e27 ("net/smc: Clear memory when release and reuse buffer")
> Signed-off-by: D. Wythe <alibuda@linux.alibaba.com>
> ---
>   net/smc/smc_core.c | 17 ++++++++---------
>   1 file changed, 8 insertions(+), 9 deletions(-)
> 
> diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c
> index c305d8d..c19d4b7 100644
> --- a/net/smc/smc_core.c
> +++ b/net/smc/smc_core.c
> @@ -1120,8 +1120,9 @@ static void smcr_buf_unuse(struct smc_buf_desc *buf_desc, bool is_rmb,
>   
>   		smc_buf_free(lgr, is_rmb, buf_desc);
>   	} else {
> -		buf_desc->used = 0;
> -		memset(buf_desc->cpu_addr, 0, buf_desc->len);
> +		/* memzero_explicit provides potential memory barrier semantics */
> +		memzero_explicit(buf_desc->cpu_addr, buf_desc->len);
> +		WRITE_ONCE(buf_desc->used, 0);
>   	}
>   }
>   
> @@ -1132,19 +1133,17 @@ static void smc_buf_unuse(struct smc_connection *conn,
>   		if (!lgr->is_smcd && conn->sndbuf_desc->is_vm) {
>   			smcr_buf_unuse(conn->sndbuf_desc, false, lgr);
>   		} else {
> -			conn->sndbuf_desc->used = 0;
> -			memset(conn->sndbuf_desc->cpu_addr, 0,
> -			       conn->sndbuf_desc->len);
> +			memzero_explicit(conn->sndbuf_desc->cpu_addr, conn->sndbuf_desc->len);
> +			WRITE_ONCE(conn->sndbuf_desc->used, 0);
>   		}
>   	}
>   	if (conn->rmb_desc) {
>   		if (!lgr->is_smcd) {
>   			smcr_buf_unuse(conn->rmb_desc, true, lgr);
>   		} else {
> -			conn->rmb_desc->used = 0;
> -			memset(conn->rmb_desc->cpu_addr, 0,
> -			       conn->rmb_desc->len +
> -			       sizeof(struct smcd_cdc_msg));
> +			memzero_explicit(conn->rmb_desc->cpu_addr,
> +					 conn->rmb_desc->len + sizeof(struct smcd_cdc_msg));
> +			WRITE_ONCE(conn->rmb_desc->used, 0);
>   		}
>   	}
>   }

Re: [PATCH net] net/smc: fix application data exception

[Wenjia Zhang]

On 26.11.22 09:22, D.Wythe wrote:
> From: "D. Wythe" <alibuda@linux.alibaba.com>
> 
> There is a certain probability that following
> exceptions will occur in the wrk benchmark test:
> 
> Running 10s test @ http://11.213.45.6:80
>    8 threads and 64 connections
>    Thread Stats   Avg      Stdev     Max   +/- Stdev
>      Latency     3.72ms   13.94ms 245.33ms   94.17%
>      Req/Sec     1.96k   713.67     5.41k    75.16%
>    155262 requests in 10.10s, 23.10MB read
> Non-2xx or 3xx responses: 3
> 
> We will find that the error is HTTP 400 error, which is a serious
> exception in our test, which means the application data was
> corrupted.
> 
> Consider the following scenarios:
> 
> CPU0                            CPU1
> 
> buf_desc->used = 0;
>                                  cmpxchg(buf_desc->used, 0, 1)
>                                  deal_with(buf_desc)
> 
> memset(buf_desc->cpu_addr,0);
> 
> This will cause the data received by a victim connection to be cleared,
> thus triggering an HTTP 400 error in the server.
> 
> This patch exchange the order between clear used and memset, add
> barrier to ensure memory consistency.
> 
> Fixes: 1c5526968e27 ("net/smc: Clear memory when release and reuse buffer")
> Signed-off-by: D. Wythe <alibuda@linux.alibaba.com>
> ---
>   net/smc/smc_core.c | 17 ++++++++---------
>   1 file changed, 8 insertions(+), 9 deletions(-)
> 
> diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c
> index c305d8d..c19d4b7 100644
> --- a/net/smc/smc_core.c
> +++ b/net/smc/smc_core.c
> @@ -1120,8 +1120,9 @@ static void smcr_buf_unuse(struct smc_buf_desc *buf_desc, bool is_rmb,
>   
>   		smc_buf_free(lgr, is_rmb, buf_desc);
>   	} else {
> -		buf_desc->used = 0;
> -		memset(buf_desc->cpu_addr, 0, buf_desc->len);
> +		/* memzero_explicit provides potential memory barrier semantics */
> +		memzero_explicit(buf_desc->cpu_addr, buf_desc->len);
> +		WRITE_ONCE(buf_desc->used, 0);
>   	}
>   }
>   
> @@ -1132,19 +1133,17 @@ static void smc_buf_unuse(struct smc_connection *conn,
>   		if (!lgr->is_smcd && conn->sndbuf_desc->is_vm) {
>   			smcr_buf_unuse(conn->sndbuf_desc, false, lgr);
>   		} else {
> -			conn->sndbuf_desc->used = 0;
> -			memset(conn->sndbuf_desc->cpu_addr, 0,
> -			       conn->sndbuf_desc->len);
> +			memzero_explicit(conn->sndbuf_desc->cpu_addr, conn->sndbuf_desc->len);
> +			WRITE_ONCE(conn->sndbuf_desc->used, 0);
>   		}
>   	}
>   	if (conn->rmb_desc) {
>   		if (!lgr->is_smcd) {
>   			smcr_buf_unuse(conn->rmb_desc, true, lgr);
>   		} else {
> -			conn->rmb_desc->used = 0;
> -			memset(conn->rmb_desc->cpu_addr, 0,
> -			       conn->rmb_desc->len +
> -			       sizeof(struct smcd_cdc_msg));
> +			memzero_explicit(conn->rmb_desc->cpu_addr,
> +					 conn->rmb_desc->len + sizeof(struct smcd_cdc_msg));
> +			WRITE_ONCE(conn->rmb_desc->used, 0);
>   		}
>   	}
>   }

Hi David,

Thank you for remembering me again about this patch. I did forget to 
answer you, sorry!

My consideration was if memzero_explicit() is necessary in this case. 
But sure, it makes sense, especiall when the dereferencing is in 
somewhere else.

Thank you for the fix!

Reviewed-by: Wenjia Zhang <wenjia@linux.ibm.com>

Re: [PATCH net] net/smc: fix application data exception

[Jakub Kicinski]

On Wed, 15 Feb 2023 10:27:55 +0100 Wenjia Zhang wrote:
> Hi David,
> 
> Thank you for remembering me again about this patch. I did forget to 
> answer you, sorry!
> 
> My consideration was if memzero_explicit() is necessary in this case. 
> But sure, it makes sense, especiall when the dereferencing is in 
> somewhere else.
> 
> Thank you for the fix!
> 
> Reviewed-by: Wenjia Zhang <wenjia@linux.ibm.com>

Thanks! David, please repost if you'd like the patch to be applied to
the networking tree. The original posting is too old to use.

Re: [PATCH net] net/smc: fix application data exception

[D. Wythe]

On 2/16/23 1:31 AM, Jakub Kicinski wrote:
> On Wed, 15 Feb 2023 10:27:55 +0100 Wenjia Zhang wrote:
>> Hi David,
>>
>> Thank you for remembering me again about this patch. I did forget to
>> answer you, sorry!
>>
>> My consideration was if memzero_explicit() is necessary in this case.
>> But sure, it makes sense, especiall when the dereferencing is in
>> somewhere else.
>>
>> Thank you for the fix!
>>
>> Reviewed-by: Wenjia Zhang <wenjia@linux.ibm.com>
> 
> Thanks! David, please repost if you'd like the patch to be applied to
> the networking tree. The original posting is too old to use.

Thank you for your reminder.  I will repost it after rebasing.
D. Wythe