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

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

[Xufeng Zhang]

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@tuxdriver.com>
Signed-off-by: Xufeng Zhang <xufeng.zhang@windriver.com>
---
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
-- 
1.7.0.2

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

[Daniel Borkmann]

On 06/12/2014 04:53 AM, 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@tuxdriver.com>
> Signed-off-by: Xufeng Zhang <xufeng.zhang@windriver.com>

Looks good to me, thanks. This also needs to go to -stable.

Acked-by: Daniel Borkmann <dborkman@redhat.com>

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

[Vlad Yasevich]

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@tuxdriver.com>
> Signed-off-by: Xufeng Zhang <xufeng.zhang@windriver.com>

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

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

[David Miller]

From: Xufeng Zhang <xufeng.zhang@windriver.com>
Date: Thu, 12 Jun 2014 10:53:36 +0800

> 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@tuxdriver.com>
> Signed-off-by: Xufeng Zhang <xufeng.zhang@windriver.com>
> ---
> Change for v2:
>   Drop the redundant test for temp suggested by Vlad Yasevich.

Applied and queued up for -stable, thanks.