[PATCH net] net: sctp: use MAX_HEADER for headroom reserve in output path

[PATCH net] net: sctp: use MAX_HEADER for headroom reserve in output path

[Daniel Borkmann]

To accomodate for enough headroom for tunnels, use MAX_HEADER instead
of LL_MAX_HEADER. Robert reported that he has hit after roughly 40hrs
of trinity an skb_under_panic() via SCTP output path (see reference).
I couldn't reproduce it from here, but not using MAX_HEADER as elsewhere
in other protocols might be one possible cause for this.

In any case, it looks like accounting on chunks themself seems to look
good as the skb already passed the SCTP output path and did not hit
any skb_over_panic(). Given tunneling was enabled in his .config, the
headroom would have been expanded by MAX_HEADER in this case.

Reported-by: Robert Święcki <robert@swiecki.net>
Reference: https://lkml.org/lkml/2014/12/1/507
Fixes: 594ccc14dfe4d ("[SCTP] Replace incorrect use of dev_alloc_skb with alloc_skb in sctp_packet_transmit().")
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
---
 net/sctp/output.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/sctp/output.c b/net/sctp/output.c
index 42dffd4..fc5e45b 100644
--- a/net/sctp/output.c
+++ b/net/sctp/output.c
@@ -401,12 +401,12 @@ int sctp_packet_transmit(struct sctp_packet *packet)
 	sk = chunk->skb->sk;
 
 	/* Allocate the new skb.  */
-	nskb = alloc_skb(packet->size + LL_MAX_HEADER, GFP_ATOMIC);
+	nskb = alloc_skb(packet->size + MAX_HEADER, GFP_ATOMIC);
 	if (!nskb)
 		goto nomem;
 
 	/* Make sure the outbound skb has enough header room reserved. */
-	skb_reserve(nskb, packet->overhead + LL_MAX_HEADER);
+	skb_reserve(nskb, packet->overhead + MAX_HEADER);
 
 	/* Set the owning socket so that we know where to get the
 	 * destination IP address.
-- 
1.7.11.7

Re: [PATCH net] net: sctp: use MAX_HEADER for headroom reserve in output path

[Vlad Yasevich]

On 12/03/2014 06:13 AM, Daniel Borkmann wrote:
> To accomodate for enough headroom for tunnels, use MAX_HEADER instead
> of LL_MAX_HEADER. Robert reported that he has hit after roughly 40hrs
> of trinity an skb_under_panic() via SCTP output path (see reference).
> I couldn't reproduce it from here, but not using MAX_HEADER as elsewhere
> in other protocols might be one possible cause for this.
> 
> In any case, it looks like accounting on chunks themself seems to look
> good as the skb already passed the SCTP output path and did not hit
> any skb_over_panic(). Given tunneling was enabled in his .config, the
> headroom would have been expanded by MAX_HEADER in this case.
> 
> Reported-by: Robert Święcki <robert@swiecki.net>
> Reference: https://lkml.org/lkml/2014/12/1/507
> Fixes: 594ccc14dfe4d ("[SCTP] Replace incorrect use of dev_alloc_skb with alloc_skb in sctp_packet_transmit().")
> Signed-off-by: Daniel Borkmann <dborkman@redhat.com>

Looks right.  If sctp path is over any kind of L3 tunnel, we'll see this.

Acked-by: Vlad Yasevich <vyasevich@gmail.com>

-vlad

> ---
>  net/sctp/output.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/net/sctp/output.c b/net/sctp/output.c
> index 42dffd4..fc5e45b 100644
> --- a/net/sctp/output.c
> +++ b/net/sctp/output.c
> @@ -401,12 +401,12 @@ int sctp_packet_transmit(struct sctp_packet *packet)
>  	sk = chunk->skb->sk;
>  
>  	/* Allocate the new skb.  */
> -	nskb = alloc_skb(packet->size + LL_MAX_HEADER, GFP_ATOMIC);
> +	nskb = alloc_skb(packet->size + MAX_HEADER, GFP_ATOMIC);
>  	if (!nskb)
>  		goto nomem;
>  
>  	/* Make sure the outbound skb has enough header room reserved. */
> -	skb_reserve(nskb, packet->overhead + LL_MAX_HEADER);
> +	skb_reserve(nskb, packet->overhead + MAX_HEADER);
>  
>  	/* Set the owning socket so that we know where to get the
>  	 * destination IP address.
> 

Re: [PATCH net] net: sctp: use MAX_HEADER for headroom reserve in output path

[Neil Horman]

On Wed, Dec 03, 2014 at 12:13:58PM +0100, Daniel Borkmann wrote:
> To accomodate for enough headroom for tunnels, use MAX_HEADER instead
> of LL_MAX_HEADER. Robert reported that he has hit after roughly 40hrs
> of trinity an skb_under_panic() via SCTP output path (see reference).
> I couldn't reproduce it from here, but not using MAX_HEADER as elsewhere
> in other protocols might be one possible cause for this.
> 
> In any case, it looks like accounting on chunks themself seems to look
> good as the skb already passed the SCTP output path and did not hit
> any skb_over_panic(). Given tunneling was enabled in his .config, the
> headroom would have been expanded by MAX_HEADER in this case.
> 
> Reported-by: Robert Święcki <robert@swiecki.net>
> Reference: https://lkml.org/lkml/2014/12/1/507
> Fixes: 594ccc14dfe4d ("[SCTP] Replace incorrect use of dev_alloc_skb with alloc_skb in sctp_packet_transmit().")
> Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
> ---
>  net/sctp/output.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/net/sctp/output.c b/net/sctp/output.c
> index 42dffd4..fc5e45b 100644
> --- a/net/sctp/output.c
> +++ b/net/sctp/output.c
> @@ -401,12 +401,12 @@ int sctp_packet_transmit(struct sctp_packet *packet)
>  	sk = chunk->skb->sk;
>  
>  	/* Allocate the new skb.  */
> -	nskb = alloc_skb(packet->size + LL_MAX_HEADER, GFP_ATOMIC);
> +	nskb = alloc_skb(packet->size + MAX_HEADER, GFP_ATOMIC);
>  	if (!nskb)
>  		goto nomem;
>  
>  	/* Make sure the outbound skb has enough header room reserved. */
> -	skb_reserve(nskb, packet->overhead + LL_MAX_HEADER);
> +	skb_reserve(nskb, packet->overhead + MAX_HEADER);
>  
>  	/* Set the owning socket so that we know where to get the
>  	 * destination IP address.
> -- 
> 1.7.11.7
> 
> --
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> 
Acked-by: Neil Horman <nhorman@tuxdriver.com>

Re: [PATCH net] net: sctp: use MAX_HEADER for headroom reserve in output path

[David Miller]

From: Daniel Borkmann <dborkman@redhat.com>
Date: Wed,  3 Dec 2014 12:13:58 +0100

> To accomodate for enough headroom for tunnels, use MAX_HEADER instead
> of LL_MAX_HEADER. Robert reported that he has hit after roughly 40hrs
> of trinity an skb_under_panic() via SCTP output path (see reference).
> I couldn't reproduce it from here, but not using MAX_HEADER as elsewhere
> in other protocols might be one possible cause for this.
> 
> In any case, it looks like accounting on chunks themself seems to look
> good as the skb already passed the SCTP output path and did not hit
> any skb_over_panic(). Given tunneling was enabled in his .config, the
> headroom would have been expanded by MAX_HEADER in this case.
> 
> Reported-by: Robert Święcki <robert@swiecki.net>
> Reference: https://lkml.org/lkml/2014/12/1/507
> Fixes: 594ccc14dfe4d ("[SCTP] Replace incorrect use of dev_alloc_skb with alloc_skb in sctp_packet_transmit().")
> Signed-off-by: Daniel Borkmann <dborkman@redhat.com>

Applied and queued up for -stable, thanks.