[PATCH net] sunrpc: fix UDP memory accounting

[PATCH net] sunrpc: fix UDP memory accounting

[Paolo Abeni]

The commit f9b2ee714c5c ("SUNRPC: Move UDP receive data path
into a workqueue context"), as a side effect, moved the
skb_free_datagram() call outside the scope of the related socket
lock, but UDP sockets require such lock to be held for proper
memory accounting.
Fix it by replacing skb_free_datagram() with
skb_free_datagram_locked().

Fixes: f9b2ee714c5c ("SUNRPC: Move UDP receive data path into a workqueue context")
Reported-and-tested-by: Jan Stancek <jstancek-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Signed-off-by: Paolo Abeni <pabeni-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 net/sunrpc/xprtsock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index 8ede3bc..bf16883 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -1074,7 +1074,7 @@ static void xs_udp_data_receive(struct sock_xprt *transport)
 		skb = skb_recv_datagram(sk, 0, 1, &err);
 		if (skb != NULL) {
 			xs_udp_data_read_skb(&transport->xprt, sk, skb);
-			skb_free_datagram(sk, skb);
+			skb_free_datagram_locked(sk, skb);
 			continue;
 		}
 		if (!test_and_clear_bit(XPRT_SOCK_DATA_READY, &transport->sock_state))
-- 
1.8.3.1

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Re: [PATCH net] sunrpc: fix UDP memory accounting

[Benjamin Coddington]

On 25 Aug 2016, at 12:42, Paolo Abeni wrote:

> The commit f9b2ee714c5c ("SUNRPC: Move UDP receive data path
> into a workqueue context"), as a side effect, moved the
> skb_free_datagram() call outside the scope of the related socket
> lock, but UDP sockets require such lock to be held for proper
> memory accounting.
> Fix it by replacing skb_free_datagram() with
> skb_free_datagram_locked().
>
> Fixes: f9b2ee714c5c ("SUNRPC: Move UDP receive data path into a 
> workqueue context")
> Reported-and-tested-by: Jan Stancek <jstancek-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> Signed-off-by: Paolo Abeni <pabeni-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>

Thanks for finding this. A similar fix in 2009 for svcsock.c was done by 
Eric Dumazet:
9d410c796067 ("net: fix sk_forward_alloc corruption")

skb_free_datagram_locked() is used for all xprt types in svcsock.c, 
should we use
it for the xs_local_transport as well in xprtsock.c?

Ben

> ---
>  net/sunrpc/xprtsock.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
> index 8ede3bc..bf16883 100644
> --- a/net/sunrpc/xprtsock.c
> +++ b/net/sunrpc/xprtsock.c
> @@ -1074,7 +1074,7 @@ static void xs_udp_data_receive(struct sock_xprt 
> *transport)
>  		skb = skb_recv_datagram(sk, 0, 1, &err);
>  		if (skb != NULL) {
>  			xs_udp_data_read_skb(&transport->xprt, sk, skb);
> -			skb_free_datagram(sk, skb);
> +			skb_free_datagram_locked(sk, skb);
>  			continue;
>  		}
>  		if (!test_and_clear_bit(XPRT_SOCK_DATA_READY, 
> &transport->sock_state))
> -- 
> 1.8.3.1
>
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Re: [PATCH net] sunrpc: fix UDP memory accounting

[Paolo Abeni]

On Tue, 2016-08-30 at 12:28 -0400, Benjamin Coddington wrote:
> On 25 Aug 2016, at 12:42, Paolo Abeni wrote:
> 
> > The commit f9b2ee714c5c ("SUNRPC: Move UDP receive data path
> > into a workqueue context"), as a side effect, moved the
> > skb_free_datagram() call outside the scope of the related socket
> > lock, but UDP sockets require such lock to be held for proper
> > memory accounting.
> > Fix it by replacing skb_free_datagram() with
> > skb_free_datagram_locked().
> >
> > Fixes: f9b2ee714c5c ("SUNRPC: Move UDP receive data path into a 
> > workqueue context")
> > Reported-and-tested-by: Jan Stancek <jstancek-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> > Signed-off-by: Paolo Abeni <pabeni-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> 
> Thanks for finding this. A similar fix in 2009 for svcsock.c was done by 
> Eric Dumazet:
> 9d410c796067 ("net: fix sk_forward_alloc corruption")
> 
> skb_free_datagram_locked() is used for all xprt types in svcsock.c, 
> should we use
> it for the xs_local_transport as well in xprtsock.c?

AFAICS a similar fix is _not_ needed for xs_local_transport(), since it
uses AF_LOCAL sockets and such family does not support protocol's memory
accounting.

Paolo

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Re: [PATCH net] sunrpc: fix UDP memory accounting

[Benjamin Coddington]

On 31 Aug 2016, at 7:45, Paolo Abeni wrote:

> On Tue, 2016-08-30 at 12:28 -0400, Benjamin Coddington wrote:
>> On 25 Aug 2016, at 12:42, Paolo Abeni wrote:
>>
>>> The commit f9b2ee714c5c ("SUNRPC: Move UDP receive data path
>>> into a workqueue context"), as a side effect, moved the
>>> skb_free_datagram() call outside the scope of the related socket
>>> lock, but UDP sockets require such lock to be held for proper
>>> memory accounting.
>>> Fix it by replacing skb_free_datagram() with
>>> skb_free_datagram_locked().
>>>
>>> Fixes: f9b2ee714c5c ("SUNRPC: Move UDP receive data path into a
>>> workqueue context")
>>> Reported-and-tested-by: Jan Stancek <jstancek-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
>>> Signed-off-by: Paolo Abeni <pabeni-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
>>
>> Thanks for finding this. A similar fix in 2009 for svcsock.c was done by
>> Eric Dumazet:
>> 9d410c796067 ("net: fix sk_forward_alloc corruption")
>>
>> skb_free_datagram_locked() is used for all xprt types in svcsock.c,
>> should we use
>> it for the xs_local_transport as well in xprtsock.c?
>
> AFAICS a similar fix is _not_ needed for xs_local_transport(), since it
> uses AF_LOCAL sockets and such family does not support protocol's memory
> accounting.

This fixes the WARNING reported by Jan Stancek here:
http://marc.info/?l=linux-nfs&m=146616830928019&w=2

Reviewed-by: Benjamin Coddington <bcodding-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>

Ben
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