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Subject: [Bug 197535] [re] [panic] if_re (Realtek 8168) causes memory write
 after free and kernel panic
Date: Wed, 25 Feb 2015 14:48:53 +0000
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=197535

--- Comment #10 from luca.pizzamiglio@gmail.com ---
Finally, I get the behavior of the my re0 interface, unfortunately, still
without solution.

When the driver gets a new descriptor on the rxring, the mbuf is still full of
0xdeadcode.

The Memory modified after free:
Memory modified after free 0xfffff800039de800(2048) val=ffffffff @
0xfffff800039de800
The value is the first 4 byte of a broadcast ethernet packet and the address is
one previously used to store a mbuf.

The first conclusion is that packets are not yet written when a rxring entry is
sent.

I've also checked why rxring entries are flying away causing page faults:
simply, the ring is acting as an array :) In other words, new entries are
always written sequentially, violating the size of the ring.
When the last element of the ring (idx=255) is used, it correctly rewritten
using 0xC0000800 instead of 0x80000800, signalling that it's the last entry of
the ring.

Any ideas?

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