[PATCH 1/4] sctp: fix association hangs due to off-by-one errors in sctp_tsnmap_grow()

[PATCH 1/4] sctp: fix association hangs due to off-by-one errors in sctp_tsnmap_grow()

[Roberts, Lee A.]

From: Lee A. Roberts <lee.roberts@hp.com>

Resolve SCTP association hangs observed during SCTP stress
testing.  Observable symptoms include communications hangs
with data being held in the association lobby (ordering)
queue.  Close examination of reassembly/ordering queues shows
duplicated packets.

In sctp_tsnmap_grow(), correct off-by-one errors when copying
and resizing the tsnmap.  If max_tsn_seen is in the LSB of the
word, this bit can be lost, causing the corresponding packet
to be transmitted again and to be entered as a duplicate into
the SCTP reassembly/ordering queues.

Patch applies to linux-3.8 kernel.

Signed-off-by: Lee A. Roberts <lee.roberts@hp.com>
---
 net/sctp/tsnmap.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff -uprN -X linux-3.8-vanilla/Documentation/dontdiff linux-3.8-vanilla/net/sctp/tsnmap.c linux-3.8-SCTP+1/net/sctp/tsnmap.c
--- linux-3.8-vanilla/net/sctp/tsnmap.c	2013-02-18 16:58:34.000000000 -0700
+++ linux-3.8-SCTP+1/net/sctp/tsnmap.c	2013-02-20 08:01:02.555223259 -0700
@@ -369,14 +369,15 @@ static int sctp_tsnmap_grow(struct sctp_
 	if (gap >= SCTP_TSN_MAP_SIZE)
 		return 0;
 
-	inc = ALIGN((gap - map->len),BITS_PER_LONG) + SCTP_TSN_MAP_INCREMENT;
+	inc = ALIGN((gap - map->len + 1), BITS_PER_LONG)
+		+ SCTP_TSN_MAP_INCREMENT;
 	len = min_t(u16, map->len + inc, SCTP_TSN_MAP_SIZE);
 
 	new = kzalloc(len>>3, GFP_ATOMIC);
 	if (!new)
 		return 0;
 
-	bitmap_copy(new, map->tsn_map, map->max_tsn_seen - map->base_tsn);
+	bitmap_copy(new, map->tsn_map, map->max_tsn_seen - map->base_tsn + 1);
 	kfree(map->tsn_map);
 	map->tsn_map = new;
 	map->len = len;

Re: [PATCH 1/4] sctp: fix association hangs due to off-by-one errors in sctp_tsnmap_grow()

[Vlad Yasevich]

On 02/21/2013 11:44 AM, Roberts, Lee A. wrote:
> From: Lee A. Roberts <lee.roberts@hp.com>
>
> Resolve SCTP association hangs observed during SCTP stress
> testing.  Observable symptoms include communications hangs
> with data being held in the association lobby (ordering)
> queue.  Close examination of reassembly/ordering queues shows
> duplicated packets.
>
> In sctp_tsnmap_grow(), correct off-by-one errors when copying
> and resizing the tsnmap.  If max_tsn_seen is in the LSB of the
> word, this bit can be lost, causing the corresponding packet
> to be transmitted again and to be entered as a duplicate into
> the SCTP reassembly/ordering queues.
>
> Patch applies to linux-3.8 kernel.
>
> Signed-off-by: Lee A. Roberts <lee.roberts@hp.com>
> ---
>   net/sctp/tsnmap.c |    5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff -uprN -X linux-3.8-vanilla/Documentation/dontdiff linux-3.8-vanilla/net/sctp/tsnmap.c linux-3.8-SCTP+1/net/sctp/tsnmap.c
> --- linux-3.8-vanilla/net/sctp/tsnmap.c	2013-02-18 16:58:34.000000000 -0700
> +++ linux-3.8-SCTP+1/net/sctp/tsnmap.c	2013-02-20 08:01:02.555223259 -0700
> @@ -369,14 +369,15 @@ static int sctp_tsnmap_grow(struct sctp_
>   	if (gap >= SCTP_TSN_MAP_SIZE)

No that I think about this a bit more, this should be gap + 1.  If you 
do that, you might as well call sctp_tsnmap_grow() with gap+1 as 
argument and then can just use the 'gap' everywhere inside.

>   		return 0;
>
> -	inc = ALIGN((gap - map->len),BITS_PER_LONG) + SCTP_TSN_MAP_INCREMENT;
> +	inc = ALIGN((gap - map->len + 1), BITS_PER_LONG)
> +		+ SCTP_TSN_MAP_INCREMENT;
>   	len = min_t(u16, map->len + inc, SCTP_TSN_MAP_SIZE);
>
>   	new = kzalloc(len>>3, GFP_ATOMIC);
>   	if (!new)
>   		return 0;
>
> -	bitmap_copy(new, map->tsn_map, map->max_tsn_seen - map->base_tsn);
> +	bitmap_copy(new, map->tsn_map, map->max_tsn_seen - map->base_tsn + 1);

Can simplify that this by using map->cumulative_tsn_ack_point instead of 
base_tsn.

-vlad

>   	kfree(map->tsn_map);
>   	map->tsn_map = new;
>   	map->len = len;
> --
> To unsubscribe from this list: send the line "unsubscribe linux-sctp" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>

RE: [PATCH 1/4] sctp: fix association hangs due to off-by-one errors in sctp_tsnmap_grow()

[Roberts, Lee A.]

Vlad,

> -----Original Message-----
> From: Vlad Yasevich [mailto:vyasevich@gmail.com]
> Sent: Thursday, February 21, 2013 10:19 AM
> To: Roberts, Lee A.
> Cc: linux-sctp@vger.kernel.org; netdev@vger.kernel.org; linux-kernel@vger.kernel.org
> Subject: Re: [PATCH 1/4] sctp: fix association hangs due to off-by-one errors in sctp_tsnmap_grow()
> 
> On 02/21/2013 11:44 AM, Roberts, Lee A. wrote:
> > From: Lee A. Roberts <lee.roberts@hp.com>
> >
> > Resolve SCTP association hangs observed during SCTP stress
> > testing.  Observable symptoms include communications hangs
> > with data being held in the association lobby (ordering)
> > queue.  Close examination of reassembly/ordering queues shows
> > duplicated packets.
> >
> > In sctp_tsnmap_grow(), correct off-by-one errors when copying
> > and resizing the tsnmap.  If max_tsn_seen is in the LSB of the
> > word, this bit can be lost, causing the corresponding packet
> > to be transmitted again and to be entered as a duplicate into
> > the SCTP reassembly/ordering queues.
> >
> > Patch applies to linux-3.8 kernel.
> >
> > Signed-off-by: Lee A. Roberts <lee.roberts@hp.com>
> > ---
> >   net/sctp/tsnmap.c |    5 +++--
> >   1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff -uprN -X linux-3.8-vanilla/Documentation/dontdiff linux-3.8-vanilla/net/sctp/tsnmap.c linux-
> 3.8-SCTP+1/net/sctp/tsnmap.c
> > --- linux-3.8-vanilla/net/sctp/tsnmap.c	2013-02-18 16:58:34.000000000 -0700
> > +++ linux-3.8-SCTP+1/net/sctp/tsnmap.c	2013-02-20 08:01:02.555223259 -0700
> > @@ -369,14 +369,15 @@ static int sctp_tsnmap_grow(struct sctp_
> >   	if (gap >= SCTP_TSN_MAP_SIZE)
> 
> No that I think about this a bit more, this should be gap + 1.  If you
> do that, you might as well call sctp_tsnmap_grow() with gap+1 as
> argument and then can just use the 'gap' everywhere inside.

I think the calculation of "gap" in sctp_tsnmap_mark() should change:

-	gap = tsn - map->base_tsn;
+	gap = tsn - map->cumulative_tsn_ack_point;

> 
> >   		return 0;
> >
> > -	inc = ALIGN((gap - map->len),BITS_PER_LONG) + SCTP_TSN_MAP_INCREMENT;
> > +	inc = ALIGN((gap - map->len + 1), BITS_PER_LONG)
> > +		+ SCTP_TSN_MAP_INCREMENT;
> >   	len = min_t(u16, map->len + inc, SCTP_TSN_MAP_SIZE);
> >
> >   	new = kzalloc(len>>3, GFP_ATOMIC);
> >   	if (!new)
> >   		return 0;
> >
> > -	bitmap_copy(new, map->tsn_map, map->max_tsn_seen - map->base_tsn);
> > +	bitmap_copy(new, map->tsn_map, map->max_tsn_seen - map->base_tsn + 1);
> 
> Can simplify that this by using map->cumulative_tsn_ack_point instead of
> base_tsn.
> 
> -vlad
> 

I changed the code to use "cumulative_tsn_ack_point" in an updated version
of the patch.

                                         -- Lee

> >   	kfree(map->tsn_map);
> >   	map->tsn_map = new;
> >   	map->len = len;
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-sctp" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> >

RE: [PATCH 1/4] sctp: fix association hangs due to off-by-one errors in sctp_tsnmap_grow()

[Roberts, Lee A.]

Vlad,

> -----Original Message-----
> From: Roberts, Lee A.
> Sent: Thursday, February 21, 2013 11:00 AM
> To: 'Vlad Yasevich'
> Cc: linux-sctp@vger.kernel.org; netdev@vger.kernel.org; linux-kernel@vger.kernel.org
> Subject: RE: [PATCH 1/4] sctp: fix association hangs due to off-by-one errors in sctp_tsnmap_grow()
> 
> Vlad,
> 
> > -----Original Message-----
> > From: Vlad Yasevich [mailto:vyasevich@gmail.com]
> > Sent: Thursday, February 21, 2013 10:19 AM
> > To: Roberts, Lee A.
> > Cc: linux-sctp@vger.kernel.org; netdev@vger.kernel.org; linux-kernel@vger.kernel.org
> > Subject: Re: [PATCH 1/4] sctp: fix association hangs due to off-by-one errors in sctp_tsnmap_grow()
> >
> > On 02/21/2013 11:44 AM, Roberts, Lee A. wrote:
> > > From: Lee A. Roberts <lee.roberts@hp.com>
> > >
> > > Resolve SCTP association hangs observed during SCTP stress
> > > testing.  Observable symptoms include communications hangs
> > > with data being held in the association lobby (ordering)
> > > queue.  Close examination of reassembly/ordering queues shows
> > > duplicated packets.
> > >
> > > In sctp_tsnmap_grow(), correct off-by-one errors when copying
> > > and resizing the tsnmap.  If max_tsn_seen is in the LSB of the
> > > word, this bit can be lost, causing the corresponding packet
> > > to be transmitted again and to be entered as a duplicate into
> > > the SCTP reassembly/ordering queues.
> > >
> > > Patch applies to linux-3.8 kernel.
> > >
> > > Signed-off-by: Lee A. Roberts <lee.roberts@hp.com>
> > > ---
> > >   net/sctp/tsnmap.c |    5 +++--
> > >   1 file changed, 3 insertions(+), 2 deletions(-)
> > >
> > > diff -uprN -X linux-3.8-vanilla/Documentation/dontdiff linux-3.8-vanilla/net/sctp/tsnmap.c linux-
> > 3.8-SCTP+1/net/sctp/tsnmap.c
> > > --- linux-3.8-vanilla/net/sctp/tsnmap.c	2013-02-18 16:58:34.000000000 -0700
> > > +++ linux-3.8-SCTP+1/net/sctp/tsnmap.c	2013-02-20 08:01:02.555223259 -0700
> > > @@ -369,14 +369,15 @@ static int sctp_tsnmap_grow(struct sctp_
> > >   	if (gap >= SCTP_TSN_MAP_SIZE)
> >
> > No that I think about this a bit more, this should be gap + 1.  If you
> > do that, you might as well call sctp_tsnmap_grow() with gap+1 as
> > argument and then can just use the 'gap' everywhere inside.
> 
> I think the calculation of "gap" in sctp_tsnmap_mark() should change:
> 
> -	gap = tsn - map->base_tsn;
> +	gap = tsn - map->cumulative_tsn_ack_point;
> 

Oops, this breaks the logic that follows.  Using "gap + 1" in the call should work.
I sent an updated patch (v3).

                                    - Lee

> >
> > >   		return 0;
> > >
> > > -	inc = ALIGN((gap - map->len),BITS_PER_LONG) + SCTP_TSN_MAP_INCREMENT;
> > > +	inc = ALIGN((gap - map->len + 1), BITS_PER_LONG)
> > > +		+ SCTP_TSN_MAP_INCREMENT;
> > >   	len = min_t(u16, map->len + inc, SCTP_TSN_MAP_SIZE);
> > >
> > >   	new = kzalloc(len>>3, GFP_ATOMIC);
> > >   	if (!new)
> > >   		return 0;
> > >
> > > -	bitmap_copy(new, map->tsn_map, map->max_tsn_seen - map->base_tsn);
> > > +	bitmap_copy(new, map->tsn_map, map->max_tsn_seen - map->base_tsn + 1);
> >
> > Can simplify that this by using map->cumulative_tsn_ack_point instead of
> > base_tsn.
> >
> > -vlad
> >
> 
> I changed the code to use "cumulative_tsn_ack_point" in an updated version
> of the patch.
> 
>                                          -- Lee
> 
> > >   	kfree(map->tsn_map);
> > >   	map->tsn_map = new;
> > >   	map->len = len;
> > > --
> > > To unsubscribe from this list: send the line "unsubscribe linux-sctp" in
> > > the body of a message to majordomo@vger.kernel.org
> > > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > >