netdev - Re: [PATCH] cls_u32: use skb_copy_bits() to dereference data safely

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Message-Id: <1275481538.14363.10.camel@bigi>
Date:	Wed, 02 Jun 2010 08:25:38 -0400
From:	jamal <hadi@...erus.ca>
To:	Changli Gao <xiaosuo@...il.com>
Cc:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH] cls_u32: use skb_copy_bits() to dereference data safely

On Wed, 2010-06-02 at 08:21 -0400, jamal wrote:

> Can we make the fix very simple please? i.e no copy bits, this is the
> fast path.

Example, something along lines of:

---
diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c
index 9627542..dde7a23 100644
--- a/net/sched/cls_u32.c
+++ b/net/sched/cls_u32.c
@@ -135,6 +135,9 @@ next_knode:
 
 for (i = n->sel.nkeys; i>0; i--, key++) {
 
+        int toff = key->off+(off2&key->offmask)- 4;
+        if (unlikely(toff > skb->len))
+              /* bailout here - needs some thought */
         if ((*(__be32*)(ptr+key->off+(off2&key->offmask))^key->v
             n = n->next;
             goto next_knode;
----


cheers,
jamal

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