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Date:      Tue, 30 Nov 2010 01:23:12 +0600
From:      Eugene Grosbein <eugen@eg.sd.rdtc.ru>
To:        Jack Vogel <jfvogel@gmail.com>
Cc:        freebsd-net <freebsd-net@freebsd.org>, Eugene Grosbein <eugen@eg.sd.rdtc.ru>
Subject:   Re: em(4) updated to version 7.1.8
Message-ID:  <20101129192312.GA33547@rdtc.ru>
In-Reply-To: <AANLkTimL1VHbjjv7a6RTdyj4VGcJxfNfTjc4fCcaSHXY@mail.gmail.com>
References:  <201011270946271408828@yahoo.com.cn> <AANLkTikG8RJQw%2Bh1SHZPs1cHGrM%2B3LfniZrdLqVoPVtr@mail.gmail.com> <AANLkTi=YjG40%2BDj7471wyv3aeXGJgoL1GC33iNaypsrW@mail.gmail.com> <AANLkTi=LgejYxRXnxLtkvB-Qfp2u%2BtySdriWHfGWPQjL@mail.gmail.com> <20101128081617.GA90332@zibbi.meraka.csir.co.za> <AANLkTinF1fovumkeXxWgaKi_bNiUCnqgWAtdaCaXELzO@mail.gmail.com> <20101129175128.GA32977@rdtc.ru> <AANLkTin4=kN27dMeWXzGUpTpx9HiZ3T-aymbyjMrsBn8@mail.gmail.com> <20101129182652.GA33150@rdtc.ru> <AANLkTimL1VHbjjv7a6RTdyj4VGcJxfNfTjc4fCcaSHXY@mail.gmail.com>

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On Mon, Nov 29, 2010 at 11:10:22AM -0800, Jack Vogel wrote:

> Not sure what code you created this from, but its not the new driver,

Yes, that's for previous version and that's what keeps my production
servers from panicing.

> things have been reorganized and I do not believe this issue exists.
> Please test with the latest.

I'd rather not risk. Here is the same check for today's RELENG_8 driver.
Please, please take a look. After several days of nearly gigabit load
it has already happened m_head was NULL here, in previous version.
Can it be possible in current version?
There is still no check before dereferencing.

--- if_em.c.orig	2010-11-30 01:16:17.000000000 +0600
+++ if_em.c	2010-11-30 01:19:09.000000000 +0600
@@ -4321,10 +4321,12 @@
                          
 	/* Reset state, keep loaded DMA map and reuse */
 	m = rbuf->m_head;
+	if(m) {
 	m->m_len = m->m_pkthdr.len = adapter->rx_mbuf_sz;
 	m->m_flags |= M_PKTHDR;
 	m->m_data = m->m_ext.ext_buf;
 	m->m_next = NULL;
+	}
 
 	return;
 }



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