netdev - Re: [PATCH v2] sctp: Fix sk_ack_backlog wrap-around problem

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Date:	Thu, 12 Jun 2014 10:29:46 -0400
From:	Vlad Yasevich <vyasevich@...il.com>
To:	Xufeng Zhang <xufeng.zhang@...driver.com>, nhorman@...driver.com,
	davem@...emloft.net
CC:	linux-sctp@...r.kernel.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] sctp: Fix sk_ack_backlog wrap-around problem

On 06/11/2014 10:53 PM, Xufeng Zhang wrote:
> Consider the scenario:
> For a TCP-style socket, while processing the COOKIE_ECHO chunk in
> sctp_sf_do_5_1D_ce(), after it has passed a series of sanity check,
> a new association would be created in sctp_unpack_cookie(), but afterwards,
> some processing maybe failed, and sctp_association_free() will be called to
> free the previously allocated association, in sctp_association_free(),
> sk_ack_backlog value is decremented for this socket, since the initial
> value for sk_ack_backlog is 0, after the decrement, it will be 65535,
> a wrap-around problem happens, and if we want to establish new associations
> afterward in the same socket, ABORT would be triggered since sctp deem the
> accept queue as full.
> Fix this issue by only decrementing sk_ack_backlog for associations in
> the endpoint's list.
> 
> Fix-suggested-by: Neil Horman <nhorman@...driver.com>
> Signed-off-by: Xufeng Zhang <xufeng.zhang@...driver.com>

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

Thanks
-vlad


> ---
> Change for v2:
>   Drop the redundant test for temp suggested by Vlad Yasevich.
> 
>  net/sctp/associola.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/net/sctp/associola.c b/net/sctp/associola.c
> index 39579c3..0b99998 100644
> --- a/net/sctp/associola.c
> +++ b/net/sctp/associola.c
> @@ -330,7 +330,7 @@ void sctp_association_free(struct sctp_association *asoc)
>  	/* Only real associations count against the endpoint, so
>  	 * don't bother for if this is a temporary association.
>  	 */
> -	if (!asoc->temp) {
> +	if (!list_empty(&asoc->asocs)) {
>  		list_del(&asoc->asocs);
>  
>  		/* Decrement the backlog value for a TCP-style listening
> 

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