From: Paolo Bonzini <pbonzini@redhat.com>
To: Li Qiang <liq3ea@gmail.com>,
Bug 1886362 <1886362@bugs.launchpad.net>,
Jason Wang <jasowang@redhat.com>
Cc: 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: Thu, 9 Jul 2020 19:36:53 +0200 [thread overview]
Message-ID: <2cbdf822-c74c-1af9-e5e6-7dd71412201e@redhat.com> (raw)
In-Reply-To: <CAKXe6S+J3nARveToQjECbwV224gs66WkqGHybUhfw35t1+V8og@mail.gmail.com>
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
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.
Paolo
next prev parent reply other threads:[~2020-07-09 17:38 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 [this message]
2020-07-10 10:37 ` Li Qiang
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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