From: Li Qiang <liq3ea@gmail.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Bug 1886362 <1886362@bugs.launchpad.net>,
Jason Wang <jasowang@redhat.com>,
Qemu Developers <qemu-devel@nongnu.org>
Subject: Re: [Bug 1886362] [NEW] Heap use-after-free in lduw_he_p through e1000e_write_to_rx_buffers
Date: Fri, 10 Jul 2020 18:37:26 +0800 [thread overview]
Message-ID: <CAKXe6S+ct7D+ibGmrAMJnqKBBKyUpwVnCem8=d=jB-0tUT-N2Q@mail.gmail.com> (raw)
In-Reply-To: <2cbdf822-c74c-1af9-e5e6-7dd71412201e@redhat.com>
Paolo Bonzini <pbonzini@redhat.com> 于2020年7月10日周五 上午1:36写道：
>
> On 09/07/20 17:51, Li Qiang wrote:
> > Maybe we should check whether the address is a RAM address in 'dma_memory_rw'?
> > But it is a hot path. I'm not sure it is right. Hope more discussion.
>
> Half of the purpose of dma-helpers.c (as opposed to address_space_*
> functions in exec.c) is exactly to support writes to MMIO. This is
Hi Paolo,
Could you please explain more about this(to support writes to MMIO).
I can just see the dma helpers with sg DMA, not related with MMIO.
> especially true of dma_blk_io, which takes care of doing the DMA via a
> bounce buffer, possibly in multiple steps and even blocking due to
> cpu_register_map_client.
>
> For dma_memory_rw this is not needed, so it only needs to handle
> QEMUSGList, but I think the design should be the same.
>
> However, this is indeed a nightmare for re-entrancy. The easiest
> solution is to delay processing of descriptors to a bottom half whenever
> MMIO is doing something complicated. This is also better for latency
> because it will free the vCPU thread more quickly and leave the work to
> the I/O thread.
Do you mean we define a per-e1000e bottom half. And in the MMIO write
or packet send
trigger this bh? So even if we again trigger the MMIO write, then
second bh will not be executed?
Thanks,
Li Qiang
>
> Paolo
>
next prev parent reply other threads:[~2020-07-10 10:39 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-06 2:44 [Bug 1886362] [NEW] Heap use-after-free in lduw_he_p through e1000e_write_to_rx_buffers Alexander Bulekov
2020-07-07 4:52 ` [Bug 1886362] " Philippe Mathieu-Daudé
2020-07-09 15:51 ` [Bug 1886362] [NEW] " Li Qiang
2020-07-09 17:36 ` Paolo Bonzini
2020-07-10 10:37 ` Li Qiang [this message]
2020-07-14 8:56 ` Jason Wang
2020-07-14 8:56 ` Jason Wang
2020-07-14 10:48 ` Li Qiang
2020-07-15 8:35 ` Jason Wang
2020-07-15 8:35 ` Jason Wang
2020-07-21 12:31 ` Peter Maydell
2020-07-21 12:31 ` Peter Maydell
2020-07-21 13:21 ` Jason Wang
2020-07-21 13:21 ` Jason Wang
2020-07-21 13:44 ` Peter Maydell
2020-07-21 13:44 ` Peter Maydell
2020-07-21 14:37 ` Alexander Bulekov
2020-07-21 14:37 ` Alexander Bulekov
2020-07-22 3:25 ` Jason Wang
2020-07-22 3:25 ` Jason Wang
2020-07-21 13:46 ` Li Qiang
2020-07-22 3:27 ` Jason Wang
2020-07-22 3:27 ` Jason Wang
2020-07-21 12:14 ` [Bug 1886362] " P J P
2021-05-26 14:34 ` Thomas Huth
2021-06-14 23:40 ` Alexander Bulekov
2021-06-15 18:19 ` Thomas Huth
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