Re: "Memory modified after free" - by whom?

From: Adrian Chadd <adrian_at_freebsd.org>
Date: Mon, 10 Dec 2012 15:21:44 -0800
On 10 December 2012 15:18,  <mdf_at_freebsd.org> wrote:
> On Mon, Dec 10, 2012 at 3:10 PM, Adrian Chadd <adrian_at_freebsd.org> wrote:
>> 9216 sounds like a jumbo frame mbuf. So the NIC is writing to an mbuf
>> after it's finalised/freed.
>>
>> I have a similar bug showing up on ath(4) RX. :(
>
> Compile with DEBUG_MEMGUARD in the kernel configuration, and then set
> vm.memguard.desc to the name of the UMA zone used for the 9216 byte
> allocations, mbuf_jumbo_9k.  This should cause a panic when the memory
> is touched after free.

Right, but I think its a _hardware_ access after the buffer has been freed..


Adrian
Received on Mon Dec 10 2012 - 22:21:46 UTC

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