netdev - Re: [Bugme-new] [Bug 33502] New: Caught 64-bit read from uninitialized memory in __alloc

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Date:	Wed, 20 Apr 2011 22:32:27 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Christian Casteyde <casteyde.christian@...e.fr>
Cc:	Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Andrew Morton <akpm@...ux-foundation.org>,
	netdev@...r.kernel.org, bugzilla-daemon@...zilla.kernel.org,
	bugme-daemon@...zilla.kernel.org,
	Vegard Nossum <vegardno@....uio.no>,
	Changli Gao <xiaosuo@...il.com>
Subject: Re: [Bugme-new] [Bug 33502] New: Caught 64-bit read from
 uninitialized memory in __alloc_skb

Le mercredi 20 avril 2011 à 21:55 +0200, Eric Dumazet a écrit :
> Le mercredi 20 avril 2011 à 21:36 +0200, Christian Casteyde a écrit :
> 
> > I'm not sure it's the same problem anyway as I've said previously.
> > I append my config file used to build this kernel.
> 
> This is not the same problem, and is a known false positive from skb
> reallocation. (skb_reserve() doesnt mark memory as initialized) 
> 
> 

Please try following patch. It's a bit tricky, because network stack has
different functions to fill bytes in skb and change pointers/offsets in
it.

Alternative would be to change pskb_expand_head() to not copy zone
between skb->head and skb->data (might contain unitialized data)

Thanks


diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 79aafbb..3f2cba4 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1252,6 +1252,7 @@ static inline int skb_tailroom(const struct sk_buff *skb)
  */
 static inline void skb_reserve(struct sk_buff *skb, int len)
 {
+	kmemcheck_mark_initialized(skb->data, len);
 	skb->data += len;
 	skb->tail += len;
 }


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