netdev - Re: [BUG] crash in 8139cp with 3.9.2 and KVM

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Message-ID: <1368769782.3301.83.camel@edumazet-glaptop>
Date:	Thu, 16 May 2013 22:49:42 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Stephen Hemminger <stephen@...workplumber.org>
Cc:	romieu@...zoreil.com, nic_swsd@...ltek.com, netdev@...r.kernel.org
Subject: Re: [BUG] crash in 8139cp with 3.9.2 and KVM

On Thu, 2013-05-16 at 21:49 -0700, Stephen Hemminger wrote:
> Seeing the following panic when using emulated 8139cp with KVM and 3.9.2 kernel.
> 
> Looks like netdev_alloc_skb_ip_align() can return a fragmented skb sometimes
> and using skb_put() on a non-linear skb causes a panic.

It looks like that len is not always less or equal to buflen.

I would try this fix :

diff --git a/drivers/net/ethernet/realtek/8139cp.c b/drivers/net/ethernet/realtek/8139cp.c
index 7d1fb9a..6488dec 100644
--- a/drivers/net/ethernet/realtek/8139cp.c
+++ b/drivers/net/ethernet/realtek/8139cp.c
@@ -494,7 +494,8 @@ rx_status_loop:
 		len = (status & 0x1fff) - 4;
 		mapping = le64_to_cpu(desc->addr);
 
-		if ((status & (FirstFrag | LastFrag)) != (FirstFrag | LastFrag)) {
+		if ((status & (FirstFrag | LastFrag)) != (FirstFrag | LastFrag) ||
+		    len > buflen) {
 			/* we don't support incoming fragmented frames.
 			 * instead, we attempt to ensure that the
 			 * pre-allocated RX skbs are properly sized such


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