Re: [PATCH] ip6_offload: check segs for NULL in ipv6_gso_segment.

[David Miller]

From: Artem Savkov 
Date: Thu,  1 Dec 2016 14:06:04 +0100

> segs needs to be checked for being NULL in ipv6_gso_segment() before calling
> skb_shinfo(segs), otherwise kernel can run into a NULL-pointer dereference:
 ...
> Signed-off-by: Artem Savkov 

Applied and queued up for -stable.

Re: [PATCH] ip6_offload: check segs for NULL in ipv6_gso_segment.

[David Miller]

From: Artem Savkov 
Date: Thu,  1 Dec 2016 14:06:04 +0100

> segs needs to be checked for being NULL in ipv6_gso_segment() before calling
> skb_shinfo(segs), otherwise kernel can run into a NULL-pointer dereference:
 ...
> Signed-off-by: Artem Savkov 

Applied and queued up for -stable.

Re: [PATCH] ip6_offload: check segs for NULL in ipv6_gso_segment.

[Artem Savkov]

On Thu, Dec 01, 2016 at 09:47:17PM -0500, Don Bowman wrote:
> I have been having this problem (4.9rc6).
> I applied this patch.
> I still have the problem.
> 
> My stack trace (attached as image, i did not get it in text) is:
> 
> ipv6_gso_segment
> skb_mac_gso_segment
> __skb_gso_segment
> validate_xmit_skb
> sch_direct_xmit
> __dev_queue_xmit
> macvlan_start
> 
>  ..
> 
> I think the macvlan is important (it does not seem to occur on my VM
> that are not macvtap).

I don't see any way that the same problem may get reproduced in
ipv6_gso_segment with that patch applied, so this must be a different
issue.

-- 
Regards,
  Artem

Re: [PATCH] ip6_offload: check segs for NULL in ipv6_gso_segment.

[Artem Savkov]

On Thu, Dec 01, 2016 at 09:47:17PM -0500, Don Bowman wrote:
> I have been having this problem (4.9rc6).
> I applied this patch.
> I still have the problem.
> 
> My stack trace (attached as image, i did not get it in text) is:
> 
> ipv6_gso_segment
> skb_mac_gso_segment
> __skb_gso_segment
> validate_xmit_skb
> sch_direct_xmit
> __dev_queue_xmit
> macvlan_start
> 
>  ..
> 
> I think the macvlan is important (it does not seem to occur on my VM
> that are not macvtap).

I don't see any way that the same problem may get reproduced in
ipv6_gso_segment with that patch applied, so this must be a different
issue.

-- 
Regards,
  Artem

Re: [PATCH] ip6_offload: check segs for NULL in ipv6_gso_segment.

[Eric Dumazet]

On Thu, 2016-12-01 at 16:07 +0100, Artem Savkov wrote:

> I am not, but this would have the same behavior as pre-07b26c9 code and
> IS_ERR_OR_NULL is used in ipv4's inet_gso_segment().

My concern might have been that IS_ERR_OR_NULL() considers the !ptr to
be unlikely.

But in this code path, we really can not tell.

segs == NULL can be quite likely in TUN case, because of DODGY bit

Commit 50c3a487d50756 replaced the perfectly fine :

if (!segs || IS_ERR(segs))

into dubious

if (IS_ERR_OR_NULL(segs))

segs = NULL is not an error, but use of IS_ERR_OR_NULL() might mislead
programmers trying to understand this code.

Re: [PATCH] ip6_offload: check segs for NULL in ipv6_gso_segment.

[Eric Dumazet]

On Thu, 2016-12-01 at 16:07 +0100, Artem Savkov wrote:

> I am not, but this would have the same behavior as pre-07b26c9 code and
> IS_ERR_OR_NULL is used in ipv4's inet_gso_segment().

My concern might have been that IS_ERR_OR_NULL() considers the !ptr to
be unlikely.

But in this code path, we really can not tell.

segs == NULL can be quite likely in TUN case, because of DODGY bit

Commit 50c3a487d50756 replaced the perfectly fine :

if (!segs || IS_ERR(segs))

into dubious

if (IS_ERR_OR_NULL(segs))

segs = NULL is not an error, but use of IS_ERR_OR_NULL() might mislead
programmers trying to understand this code.

Re: [PATCH] ip6_offload: check segs for NULL in ipv6_gso_segment.

[Eric Dumazet]

On Thu, 2016-12-01 at 06:34 -0800, Eric Dumazet wrote:
> On Thu, 2016-12-01 at 14:06 +0100, Artem Savkov wrote:
> > segs needs to be checked for being NULL in ipv6_gso_segment() before calling
> > skb_shinfo(segs), otherwise kernel can run into a NULL-pointer dereference:
> 
> 
> > Signed-off-by: Artem Savkov 
> > ---
> >  
> 
> > diff --git a/net/ipv6/ip6_offload.c b/net/ipv6/ip6_offload.c
> > index 1fcf61f..89c59e6 100644
> > --- a/net/ipv6/ip6_offload.c
> > +++ b/net/ipv6/ip6_offload.c
> > @@ -99,7 +99,7 @@ static struct sk_buff *ipv6_gso_segment(struct sk_buff 
> > *skb,
> > segs = ops->callbacks.gso_segment(skb, features);
> > }
> >  
> > -   if (IS_ERR(segs))
> > +   if (IS_ERR_OR_NULL(segs))
> > goto out;
> >  
> > gso_partial = !!(skb_shinfo(segs)->gso_type & SKB_GSO_PARTIAL);
> 
> Do you know when was this bug added ?
> 
> Are you sure this is the right fix ?
> 
> Which gso_segment() is returning NULL exactly ?

Oh never mind.

This is the same fix than 576a30eb64534 but applied to IPv6.

Thanks !

Acked-by: Eric Dumazet 

Re: [PATCH] ip6_offload: check segs for NULL in ipv6_gso_segment.

[Eric Dumazet]

On Thu, 2016-12-01 at 06:34 -0800, Eric Dumazet wrote:
> On Thu, 2016-12-01 at 14:06 +0100, Artem Savkov wrote:
> > segs needs to be checked for being NULL in ipv6_gso_segment() before calling
> > skb_shinfo(segs), otherwise kernel can run into a NULL-pointer dereference:
> 
> 
> > Signed-off-by: Artem Savkov 
> > ---
> >  
> 
> > diff --git a/net/ipv6/ip6_offload.c b/net/ipv6/ip6_offload.c
> > index 1fcf61f..89c59e6 100644
> > --- a/net/ipv6/ip6_offload.c
> > +++ b/net/ipv6/ip6_offload.c
> > @@ -99,7 +99,7 @@ static struct sk_buff *ipv6_gso_segment(struct sk_buff 
> > *skb,
> > segs = ops->callbacks.gso_segment(skb, features);
> > }
> >  
> > -   if (IS_ERR(segs))
> > +   if (IS_ERR_OR_NULL(segs))
> > goto out;
> >  
> > gso_partial = !!(skb_shinfo(segs)->gso_type & SKB_GSO_PARTIAL);
> 
> Do you know when was this bug added ?
> 
> Are you sure this is the right fix ?
> 
> Which gso_segment() is returning NULL exactly ?

Oh never mind.

This is the same fix than 576a30eb64534 but applied to IPv6.

Thanks !

Acked-by: Eric Dumazet 

Re: [PATCH] ip6_offload: check segs for NULL in ipv6_gso_segment.

[Artem Savkov]

On Thu, Dec 01, 2016 at 06:34:07AM -0800, Eric Dumazet wrote:
> On Thu, 2016-12-01 at 14:06 +0100, Artem Savkov wrote:
> > segs needs to be checked for being NULL in ipv6_gso_segment() before calling
> > skb_shinfo(segs), otherwise kernel can run into a NULL-pointer dereference:
> 
> 
> > Signed-off-by: Artem Savkov 
> > ---
> >  
> 
> > diff --git a/net/ipv6/ip6_offload.c b/net/ipv6/ip6_offload.c
> > index 1fcf61f..89c59e6 100644
> > --- a/net/ipv6/ip6_offload.c
> > +++ b/net/ipv6/ip6_offload.c
> > @@ -99,7 +99,7 @@ static struct sk_buff *ipv6_gso_segment(struct sk_buff 
> > *skb,
> > segs = ops->callbacks.gso_segment(skb, features);
> > }
> >  
> > -   if (IS_ERR(segs))
> > +   if (IS_ERR_OR_NULL(segs))
> > goto out;
> >  
> > gso_partial = !!(skb_shinfo(segs)->gso_type & SKB_GSO_PARTIAL);
> 
> Do you know when was this bug added ?

It started to show up with 4.9-rc4, from what I see the culprit is
07b26c9 gso: Support partial splitting at the frag_list pointer

> Are you sure this is the right fix ?

I am not, but this would have the same behavior as pre-07b26c9 code and
IS_ERR_OR_NULL is used in ipv4's inet_gso_segment().

> Which gso_segment() is returning NULL exactly ?

Unfortunatelly I don't know that and I don't have a good reproducer, the
only way to reproduce this that I currently have is calling
virt-install.

-- 
Regards,
  Artem

Re: [PATCH] ip6_offload: check segs for NULL in ipv6_gso_segment.

[Artem Savkov]

On Thu, Dec 01, 2016 at 06:34:07AM -0800, Eric Dumazet wrote:
> On Thu, 2016-12-01 at 14:06 +0100, Artem Savkov wrote:
> > segs needs to be checked for being NULL in ipv6_gso_segment() before calling
> > skb_shinfo(segs), otherwise kernel can run into a NULL-pointer dereference:
> 
> 
> > Signed-off-by: Artem Savkov 
> > ---
> >  
> 
> > diff --git a/net/ipv6/ip6_offload.c b/net/ipv6/ip6_offload.c
> > index 1fcf61f..89c59e6 100644
> > --- a/net/ipv6/ip6_offload.c
> > +++ b/net/ipv6/ip6_offload.c
> > @@ -99,7 +99,7 @@ static struct sk_buff *ipv6_gso_segment(struct sk_buff 
> > *skb,
> > segs = ops->callbacks.gso_segment(skb, features);
> > }
> >  
> > -   if (IS_ERR(segs))
> > +   if (IS_ERR_OR_NULL(segs))
> > goto out;
> >  
> > gso_partial = !!(skb_shinfo(segs)->gso_type & SKB_GSO_PARTIAL);
> 
> Do you know when was this bug added ?

It started to show up with 4.9-rc4, from what I see the culprit is
07b26c9 gso: Support partial splitting at the frag_list pointer

> Are you sure this is the right fix ?

I am not, but this would have the same behavior as pre-07b26c9 code and
IS_ERR_OR_NULL is used in ipv4's inet_gso_segment().

> Which gso_segment() is returning NULL exactly ?

Unfortunatelly I don't know that and I don't have a good reproducer, the
only way to reproduce this that I currently have is calling
virt-install.

-- 
Regards,
  Artem

Re: [PATCH] ip6_offload: check segs for NULL in ipv6_gso_segment.

[Eric Dumazet]

On Thu, 2016-12-01 at 14:06 +0100, Artem Savkov wrote:
> segs needs to be checked for being NULL in ipv6_gso_segment() before calling
> skb_shinfo(segs), otherwise kernel can run into a NULL-pointer dereference:


> Signed-off-by: Artem Savkov 
> ---
>  

> diff --git a/net/ipv6/ip6_offload.c b/net/ipv6/ip6_offload.c
> index 1fcf61f..89c59e6 100644
> --- a/net/ipv6/ip6_offload.c
> +++ b/net/ipv6/ip6_offload.c
> @@ -99,7 +99,7 @@ static struct sk_buff *ipv6_gso_segment(struct sk_buff *skb,
>   segs = ops->callbacks.gso_segment(skb, features);
>   }
>  
> - if (IS_ERR(segs))
> + if (IS_ERR_OR_NULL(segs))
>   goto out;
>  
>   gso_partial = !!(skb_shinfo(segs)->gso_type & SKB_GSO_PARTIAL);

Do you know when was this bug added ?

Are you sure this is the right fix ?

Which gso_segment() is returning NULL exactly ?

Thanks.

Re: [PATCH] ip6_offload: check segs for NULL in ipv6_gso_segment.

[Eric Dumazet]

On Thu, 2016-12-01 at 14:06 +0100, Artem Savkov wrote:
> segs needs to be checked for being NULL in ipv6_gso_segment() before calling
> skb_shinfo(segs), otherwise kernel can run into a NULL-pointer dereference:


> Signed-off-by: Artem Savkov 
> ---
>  

> diff --git a/net/ipv6/ip6_offload.c b/net/ipv6/ip6_offload.c
> index 1fcf61f..89c59e6 100644
> --- a/net/ipv6/ip6_offload.c
> +++ b/net/ipv6/ip6_offload.c
> @@ -99,7 +99,7 @@ static struct sk_buff *ipv6_gso_segment(struct sk_buff *skb,
>   segs = ops->callbacks.gso_segment(skb, features);
>   }
>  
> - if (IS_ERR(segs))
> + if (IS_ERR_OR_NULL(segs))
>   goto out;
>  
>   gso_partial = !!(skb_shinfo(segs)->gso_type & SKB_GSO_PARTIAL);

Do you know when was this bug added ?

Are you sure this is the right fix ?

Which gso_segment() is returning NULL exactly ?

Thanks.