Re: [PATCH v2] xfrm: Reset secpath in xfrm failure

[Myungho Jung <mhjungk@gmail.com>]

On Wed, Mar 06, 2019 at 02:31:25PM -0800, Eric Dumazet wrote:
> 
> 
> On 03/06/2019 01:55 PM, Myungho Jung wrote:
> > In esp4_gro_receive() and esp6_gro_receive(), secpath can be allocated
> > without adding xfrm state to xvec. Then, sp->xvec[sp->len - 1] would
> > fail and result in dereferencing invalid pointer in esp4_gso_segment()
> > and esp6_gso_segment(). Reset secpath if xfrm function returns error.
> > 
> > Fixes: 7785bba299a8 ("esp: Add a software GRO codepath")
> > Reported-by: syzbot+b69368fd933c6c592f4c@syzkaller.appspotmail.com
> > Signed-off-by: Myungho Jung <mhjungk@gmail.com>
> > ---
> > Changes in v2:
> >   - Add fixes tag.
> > 
> >  net/ipv4/esp4_offload.c | 9 +++++++--
> >  net/ipv6/esp6_offload.c | 9 +++++++--
> >  2 files changed, 14 insertions(+), 4 deletions(-)
> > 
> > diff --git a/net/ipv4/esp4_offload.c b/net/ipv4/esp4_offload.c
> > index 8756e0e790d2..7329e40c73f6 100644
> > --- a/net/ipv4/esp4_offload.c
> > +++ b/net/ipv4/esp4_offload.c
> > @@ -51,14 +51,18 @@ static struct sk_buff *esp4_gro_receive(struct list_head *head,
> >  		if (!sp)
> >  			goto out;
> >  
> > -		if (sp->len == XFRM_MAX_DEPTH)
> > +		if (sp->len == XFRM_MAX_DEPTH) {
> > +			secpath_reset(skb);
> >  			goto out;
> > +		}
> >  
> >  		x = xfrm_state_lookup(dev_net(skb->dev), skb->mark,
> >  				      (xfrm_address_t *)&ip_hdr(skb)->daddr,
> >  				      spi, IPPROTO_ESP, AF_INET);
> > -		if (!x)
> > +		if (!x) {
> > +			secpath_reset(skb);
> >  			goto out;
> > +		}
> >  
> 
> I suggest another exit label, so that you replace "goto out" by "goto out_reset";
> 
> diff --git a/net/ipv4/esp4_offload.c b/net/ipv4/esp4_offload.c
> index 8756e0e790d2a94a5b4a587c3bc3de0673baf2c4..76f754f6692696ba2aa8c9eb03b68b92d1e39ee1 100644
> --- a/net/ipv4/esp4_offload.c
> +++ b/net/ipv4/esp4_offload.c
> @@ -82,6 +82,8 @@ static struct sk_buff *esp4_gro_receive(struct list_head *head,
>         xfrm_input(skb, IPPROTO_ESP, spi, -2);
>  
>         return ERR_PTR(-EINPROGRESS);
> +out_reset:
> +       secpath_reset(skb);
>  out:
>         skb_push(skb, offset);
>         NAPI_GRO_CB(skb)->same_flow = 0;
> 
> 
> 
> 
> >  		sp->xvec[sp->len++] = x;
> >  		sp->olen++;
> > @@ -66,6 +70,7 @@ static struct sk_buff *esp4_gro_receive(struct list_head *head,
> >  		xo = xfrm_offload(skb);
> >  		if (!xo) {
> >  			xfrm_state_put(x);
> > +			secpath_reset(skb);
> >  			goto out;
> >  		}
> >  	}
> 
> 

Hi Eric,

Thanks for the suggestion. It looks better and clean. Let me update the fix to
v3.

Thanks,
Myungho