skb->truesize assertion checking for TCP

skb->truesize assertion checking for TCP

[David S. Miller]

Herbert what do you think of this?

I know it might be better to check this right where we
make the manipulations, but this catch-all trap at the
end points seems to make sense and will catch other kinds
of errors.

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index c4619a4..60a7c5a 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -344,6 +344,13 @@ extern void	      skb_over_panic(struct 
 				     void *here);
 extern void	      skb_under_panic(struct sk_buff *skb, int len,
 				      void *here);
+extern void	      skb_truesize_bug(struct sk_buff *skb);
+
+static inline void skb_truesize_check(struct sk_buff *skb)
+{
+	if (unlikely((int)skb->truesize < sizeof(struct sk_buff)))
+		skb_truesize_bug(skb);
+}
 
 extern int skb_append_datato_frags(struct sock *sk, struct sk_buff *skb,
 			int getfrag(void *from, char *to, int offset,
diff --git a/include/net/sock.h b/include/net/sock.h
index af2b054..ff8b0da 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -454,6 +454,7 @@ static inline void sk_stream_set_owner_r
 
 static inline void sk_stream_free_skb(struct sock *sk, struct sk_buff *skb)
 {
+	skb_truesize_check(skb);
 	sock_set_flag(sk, SOCK_QUEUE_SHRUNK);
 	sk->sk_wmem_queued   -= skb->truesize;
 	sk->sk_forward_alloc += skb->truesize;
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 09464fa..f2b4238 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -112,6 +112,12 @@ void skb_under_panic(struct sk_buff *skb
 	BUG();
 }
 
+void skb_truesize_bug(struct sk_buff *skb)
+{
+	printk("SKB BUG: Invalid truesize (%u) sizeof(sk_buff)=%Zd\n",
+	       skb->truesize, sizeof(struct sk_buff));
+}
+
 /* 	Allocate a new skbuff. We do this ourselves so we can fill in a few
  *	'private' fields and also do memory statistics to find all the
  *	[BEEP] leaks.
diff --git a/net/core/stream.c b/net/core/stream.c
index 35e2525..e948969 100644
--- a/net/core/stream.c
+++ b/net/core/stream.c
@@ -176,6 +176,7 @@ void sk_stream_rfree(struct sk_buff *skb
 {
 	struct sock *sk = skb->sk;
 
+	skb_truesize_check(skb);
 	atomic_sub(skb->truesize, &sk->sk_rmem_alloc);
 	sk->sk_forward_alloc += skb->truesize;
 }

Re: skb->truesize assertion checking for TCP

[Herbert Xu]

Hi David:

On Wed, Apr 19, 2006 at 09:55:13PM -0700, David S. Miller wrote:
> 
> Herbert what do you think of this?
> 
> I know it might be better to check this right where we
> make the manipulations, but this catch-all trap at the
> end points seems to make sense and will catch other kinds
> of errors.

Yes that should do the trick.

> +static inline void skb_truesize_check(struct sk_buff *skb)
> +{
> +	if (unlikely((int)skb->truesize < sizeof(struct sk_buff)))
> +		skb_truesize_bug(skb);
> +}

I think we can go for the stronger test:

skb->truesize < sizeof(struct sk_buff) + skb->len

> +void skb_truesize_bug(struct sk_buff *skb)
> +{
> +	printk("SKB BUG: Invalid truesize (%u) sizeof(sk_buff)=%Zd\n",
> +	       skb->truesize, sizeof(struct sk_buff));
> +}

Printing out skb->len would be good too if we changed the test.

Thanks,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: skb->truesize assertion checking for TCP

[David S. Miller]

From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Thu, 20 Apr 2006 15:04:06 +1000

> On Wed, Apr 19, 2006 at 09:55:13PM -0700, David S. Miller wrote:
> > +static inline void skb_truesize_check(struct sk_buff *skb)
> > +{
> > +	if (unlikely((int)skb->truesize < sizeof(struct sk_buff)))
> > +		skb_truesize_bug(skb);
> > +}
> 
> I think we can go for the stronger test:
> 
> skb->truesize < sizeof(struct sk_buff) + skb->len

Agreed, let me see if that triggers on my machine before
I commit this :-)

Re: skb->truesize assertion checking for TCP

[Jesse Brandeburg]

On 4/19/06, David S. Miller <davem@davemloft.net> wrote:
> From: Herbert Xu <herbert@gondor.apana.org.au>
> Date: Thu, 20 Apr 2006 15:04:06 +1000
>
> > On Wed, Apr 19, 2006 at 09:55:13PM -0700, David S. Miller wrote:
> > > +static inline void skb_truesize_check(struct sk_buff *skb)
> > > +{
> > > +   if (unlikely((int)skb->truesize < sizeof(struct sk_buff)))
> > > +           skb_truesize_bug(skb);
> > > +}
> >
> > I think we can go for the stronger test:
> >
> > skb->truesize < sizeof(struct sk_buff) + skb->len
>
> Agreed, let me see if that triggers on my machine before
> I commit this :-)

Um, I get a log full of these now with the 7.0.33 driver in the
kernel.  BTW, it seems like it is missing a WARN_ON or
printk(__function__) - or whatever prints the function name of a
caller in the debug output.

Apr 24 15:48:36 lindenhurst-2 kernel: e1000: eth1:
e1000_watchdog_task: NIC Link is Up 100 Mbps Half Duplex
Apr 24 15:48:36 lindenhurst-2 kernel: e1000: eth1:
e1000_watchdog_task: 10/100 speed: disabling TSO
Apr 24 15:49:21 lindenhurst-2 kernel: SKB BUG: Invalid truesize (616)
len=1448, sizeof(sk_buff)=232
Apr 24 15:49:21 lindenhurst-2 last message repeated 13 times
Apr 24 15:49:21 lindenhurst-2 kernel: SKB BUG: Invalid truesize (616)
len=1408, sizeof(sk_buff)=232
Apr 24 15:49:21 lindenhurst-2 kernel: SKB BUG: Invalid truesize (616)
len=1448, sizeof(sk_buff)=232
Apr 24 15:49:21 lindenhurst-2 last message repeated 15 times
Apr 24 15:49:21 lindenhurst-2 kernel: SKB BUG: Invalid truesize (616)
len=1408, sizeof(sk_buff)=232
Apr 24 15:49:21 lindenhurst-2 kernel: SKB BUG: Invalid truesize (616)
len=1448, sizeof(sk_buff)=232
Apr 24 15:49:21 lindenhurst-2 last message repeated 97 times

I have the latest version of net/core/skbuff.c in git.

I've verified that the below patch fixes the message appearing but I
still think the message could be refined a little bit.  We're working
on seperate patches for this for 17-rc and 16 stable.

Jesse

PS this is just for reference, this patch is mangled due to cut/paste

 drivers/net/e1000/e1000_main.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/drivers/net/e1000/e1000_main.c b/drivers/net/e1000/e1000_main.c
index add8dc4..c99e878 100644
--- a/drivers/net/e1000/e1000_main.c
+++ b/drivers/net/e1000/e1000_main.c
@@ -3768,6 +3768,7 @@ e1000_clean_rx_irq_ps(struct e1000_adapt
                        ps_page->ps_page[j] = NULL;
                        skb->len += length;
                        skb->data_len += length;
+                       skb->truesize += length;
                }

 copydone: