[03/11] ocfs2/o2net: incorrect to terminate accepting connections loop upon rejecting an invalid one
diff mbox

Message ID 20140124204702.9871031C2C7@corp2gmr1-1.hot.corp.google.com
State New, archived
Headers show

Commit Message

Andrew Morton Jan. 24, 2014, 8:47 p.m. UTC
From: Tariq Saeed <tariq.x.saeed@oracle.com>
Subject: ocfs2/o2net: incorrect to terminate accepting connections loop upon rejecting an invalid one

When o2net-accept-one() rejects an illegal connection, it terminates the
loop picking up the remaining queued connections.  This fix will continue
accepting connections till the queue is emtpy.

Addresses Orabug 17489469.

Signed-off-by: Tariq Saseed <tariq.x.saeed@oracle.com>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/ocfs2/cluster/tcp.c |   13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

Comments

Mark Fasheh Jan. 24, 2014, 9:55 p.m. UTC | #1
On Fri, Jan 24, 2014 at 12:47:02PM -0800, akpm@linux-foundation.org wrote:
> From: Tariq Saeed <tariq.x.saeed@oracle.com>
> Subject: ocfs2/o2net: incorrect to terminate accepting connections loop upon rejecting an invalid one
> 
> When o2net-accept-one() rejects an illegal connection, it terminates the
> loop picking up the remaining queued connections.  This fix will continue
> accepting connections till the queue is emtpy.
> 
> Addresses Orabug 17489469.

Thanks for sending this, review comments below.


> diff -puN fs/ocfs2/cluster/tcp.c~ocfs2-o2net-incorrect-to-terminate-accepting-connections-loop-upon-rejecting-an-invalid-one fs/ocfs2/cluster/tcp.c
> --- a/fs/ocfs2/cluster/tcp.c~ocfs2-o2net-incorrect-to-terminate-accepting-connections-loop-upon-rejecting-an-invalid-one
> +++ a/fs/ocfs2/cluster/tcp.c
> @@ -1826,7 +1826,7 @@ int o2net_register_hb_callbacks(void)
>  
>  /* ------------------------------------------------------------ */
>  
> -static int o2net_accept_one(struct socket *sock)
> +static int o2net_accept_one(struct socket *sock, int *more)
>  {
>  	int ret, slen;
>  	struct sockaddr_in sin;
> @@ -1837,6 +1837,7 @@ static int o2net_accept_one(struct socke
>  	struct o2net_node *nn;
>  
>  	BUG_ON(sock == NULL);
> +	*more = 0;
>  	ret = sock_create_lite(sock->sk->sk_family, sock->sk->sk_type,
>  			       sock->sk->sk_protocol, &new_sock);
>  	if (ret)
> @@ -1848,6 +1849,7 @@ static int o2net_accept_one(struct socke
>  	if (ret < 0)
>  		goto out;
>  
> +	*more = 1;
>  	new_sock->sk->sk_allocation = GFP_ATOMIC;
>  
>  	ret = o2net_set_nodelay(new_sock);
> @@ -1949,8 +1951,15 @@ out:
>  static void o2net_accept_many(struct work_struct *work)
>  {
>  	struct socket *sock = o2net_listen_sock;
> -	while (o2net_accept_one(sock) == 0)
> +	int	more;
> +	int	err;
> +
> +	for (;;) {
> +		err = o2net_accept_one(sock, &more);
> +		if (!more)
> +			break;

We're throwing out 'err' here and trusting the variable 'more'. However, err
could be set and more would be 0 regardless of whether there actually are
more connections to be had. This makes more sense given when 'more' is set:

	if (err)
		break;
	/* only trust the value of 'more' when err == 0 */
	if (more)
		break;

Thanks,
	--Mark

--
Mark Fasheh
Srinivas Eeda Jan. 24, 2014, 10:15 p.m. UTC | #2
On 01/24/2014 01:55 PM, Mark Fasheh wrote:
> On Fri, Jan 24, 2014 at 12:47:02PM -0800, akpm@linux-foundation.org wrote:
>> From: Tariq Saeed <tariq.x.saeed@oracle.com>
>> Subject: ocfs2/o2net: incorrect to terminate accepting connections loop upon rejecting an invalid one
>>
>> When o2net-accept-one() rejects an illegal connection, it terminates the
>> loop picking up the remaining queued connections.  This fix will continue
>> accepting connections till the queue is emtpy.
>>
>> Addresses Orabug 17489469.
> Thanks for sending this, review comments below.
>
>
>> diff -puN fs/ocfs2/cluster/tcp.c~ocfs2-o2net-incorrect-to-terminate-accepting-connections-loop-upon-rejecting-an-invalid-one fs/ocfs2/cluster/tcp.c
>> --- a/fs/ocfs2/cluster/tcp.c~ocfs2-o2net-incorrect-to-terminate-accepting-connections-loop-upon-rejecting-an-invalid-one
>> +++ a/fs/ocfs2/cluster/tcp.c
>> @@ -1826,7 +1826,7 @@ int o2net_register_hb_callbacks(void)
>>   
>>   /* ------------------------------------------------------------ */
>>   
>> -static int o2net_accept_one(struct socket *sock)
>> +static int o2net_accept_one(struct socket *sock, int *more)
>>   {
>>   	int ret, slen;
>>   	struct sockaddr_in sin;
>> @@ -1837,6 +1837,7 @@ static int o2net_accept_one(struct socke
>>   	struct o2net_node *nn;
>>   
>>   	BUG_ON(sock == NULL);
>> +	*more = 0;
>>   	ret = sock_create_lite(sock->sk->sk_family, sock->sk->sk_type,
>>   			       sock->sk->sk_protocol, &new_sock);
>>   	if (ret)
>> @@ -1848,6 +1849,7 @@ static int o2net_accept_one(struct socke
>>   	if (ret < 0)
>>   		goto out;
>>   
>> +	*more = 1;
>>   	new_sock->sk->sk_allocation = GFP_ATOMIC;
>>   
>>   	ret = o2net_set_nodelay(new_sock);
>> @@ -1949,8 +1951,15 @@ out:
>>   static void o2net_accept_many(struct work_struct *work)
>>   {
>>   	struct socket *sock = o2net_listen_sock;
>> -	while (o2net_accept_one(sock) == 0)
>> +	int	more;
>> +	int	err;
>> +
>> +	for (;;) {
>> +		err = o2net_accept_one(sock, &more);
>> +		if (!more)
>> +			break;
> We're throwing out 'err' here and trusting the variable 'more'. However, err
> could be set and more would be 0 regardless of whether there actually are
> more connections to be had. This makes more sense given when 'more' is set:
Hi Mark,

thanks for reviewing this :). Please correct me if I am wrong.

The idea was if "accept" itself fails exit the loop, otherwise continue 
scanning all queued connections. For eg: if a connection request from 
unknown node followed by known node happens at the same time, we can 
ignore the ret value of the first connection request and still continue 
accepting the next connection.

ret value appears to be of not much importance other than just for 
logging or debugging purpose.


>
> 	if (err)
> 		break;
> 	/* only trust the value of 'more' when err == 0 */
> 	if (more)
> 		break;
>
> Thanks,
> 	--Mark
>
> --
> Mark Fasheh
>
> _______________________________________________
> Ocfs2-devel mailing list
> Ocfs2-devel@oss.oracle.com
> https://oss.oracle.com/mailman/listinfo/ocfs2-devel
Tariq Saeed Jan. 24, 2014, 10:22 p.m. UTC | #3
Thanks for the comments.
To understand the consequences of ignoring the err, we need to look at 
what is going on.
We get a softIRQ when a connection packet (tcp SYN). It is critical to 
note that we may not
get a softIRQ_for every connection s_ince connection packets can arrive
back-to-back (as happened in this bug). So, one softIRQ could be 
delivered for > 1 pending accept.
_This is the KEY point. _

If we terminate the loop calling o2net_accept_one() upon seeing an 
error, what happens
to the rest of the connections in the queue. If no new connection 
arrives for hours, no new softIRQ
will be delivered, and the connections will just sit in the queue.

Thanks,
-Tariq


On 1/24/2014 1:55 PM, Mark Fasheh wrote:
> On Fri, Jan 24, 2014 at 12:47:02PM -0800, akpm@linux-foundation.org wrote:
>> From: Tariq Saeed <tariq.x.saeed@oracle.com>
>> Subject: ocfs2/o2net: incorrect to terminate accepting connections loop upon rejecting an invalid one
>>
>> When o2net-accept-one() rejects an illegal connection, it terminates the
>> loop picking up the remaining queued connections.  This fix will continue
>> accepting connections till the queue is emtpy.
>>
>> Addresses Orabug 17489469.
> Thanks for sending this, review comments below.
>
>
>> diff -puN fs/ocfs2/cluster/tcp.c~ocfs2-o2net-incorrect-to-terminate-accepting-connections-loop-upon-rejecting-an-invalid-one fs/ocfs2/cluster/tcp.c
>> --- a/fs/ocfs2/cluster/tcp.c~ocfs2-o2net-incorrect-to-terminate-accepting-connections-loop-upon-rejecting-an-invalid-one
>> +++ a/fs/ocfs2/cluster/tcp.c
>> @@ -1826,7 +1826,7 @@ int o2net_register_hb_callbacks(void)
>>   
>>   /* ------------------------------------------------------------ */
>>   
>> -static int o2net_accept_one(struct socket *sock)
>> +static int o2net_accept_one(struct socket *sock, int *more)
>>   {
>>   	int ret, slen;
>>   	struct sockaddr_in sin;
>> @@ -1837,6 +1837,7 @@ static int o2net_accept_one(struct socke
>>   	struct o2net_node *nn;
>>   
>>   	BUG_ON(sock == NULL);
>> +	*more = 0;
>>   	ret = sock_create_lite(sock->sk->sk_family, sock->sk->sk_type,
>>   			       sock->sk->sk_protocol, &new_sock);
>>   	if (ret)
>> @@ -1848,6 +1849,7 @@ static int o2net_accept_one(struct socke
>>   	if (ret < 0)
>>   		goto out;
>>   
>> +	*more = 1;
>>   	new_sock->sk->sk_allocation = GFP_ATOMIC;
>>   
>>   	ret = o2net_set_nodelay(new_sock);
>> @@ -1949,8 +1951,15 @@ out:
>>   static void o2net_accept_many(struct work_struct *work)
>>   {
>>   	struct socket *sock = o2net_listen_sock;
>> -	while (o2net_accept_one(sock) == 0)
>> +	int	more;
>> +	int	err;
>> +
>> +	for (;;) {
>> +		err = o2net_accept_one(sock, &more);
>> +		if (!more)
>> +			break;
> We're throwing out 'err' here and trusting the variable 'more'. However, err
> could be set and more would be 0 regardless of whether there actually are
> more connections to be had. This makes more sense given when 'more' is set:
>
> 	if (err)
> 		break;
> 	/* only trust the value of 'more' when err == 0 */
> 	if (more)
> 		break;
>
> Thanks,
> 	--Mark
>
> --
> Mark Fasheh

Patch
diff mbox

diff -puN fs/ocfs2/cluster/tcp.c~ocfs2-o2net-incorrect-to-terminate-accepting-connections-loop-upon-rejecting-an-invalid-one fs/ocfs2/cluster/tcp.c
--- a/fs/ocfs2/cluster/tcp.c~ocfs2-o2net-incorrect-to-terminate-accepting-connections-loop-upon-rejecting-an-invalid-one
+++ a/fs/ocfs2/cluster/tcp.c
@@ -1826,7 +1826,7 @@  int o2net_register_hb_callbacks(void)
 
 /* ------------------------------------------------------------ */
 
-static int o2net_accept_one(struct socket *sock)
+static int o2net_accept_one(struct socket *sock, int *more)
 {
 	int ret, slen;
 	struct sockaddr_in sin;
@@ -1837,6 +1837,7 @@  static int o2net_accept_one(struct socke
 	struct o2net_node *nn;
 
 	BUG_ON(sock == NULL);
+	*more = 0;
 	ret = sock_create_lite(sock->sk->sk_family, sock->sk->sk_type,
 			       sock->sk->sk_protocol, &new_sock);
 	if (ret)
@@ -1848,6 +1849,7 @@  static int o2net_accept_one(struct socke
 	if (ret < 0)
 		goto out;
 
+	*more = 1;
 	new_sock->sk->sk_allocation = GFP_ATOMIC;
 
 	ret = o2net_set_nodelay(new_sock);
@@ -1949,8 +1951,15 @@  out:
 static void o2net_accept_many(struct work_struct *work)
 {
 	struct socket *sock = o2net_listen_sock;
-	while (o2net_accept_one(sock) == 0)
+	int	more;
+	int	err;
+
+	for (;;) {
+		err = o2net_accept_one(sock, &more);
+		if (!more)
+			break;
 		cond_resched();
+	}
 }
 
 static void o2net_listen_data_ready(struct sock *sk, int bytes)