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Re: [RFC PATCH 2/3] hw/audio/intel-hda: Restrict DMA engine to memories


From: Thomas Huth
Subject: Re: [RFC PATCH 2/3] hw/audio/intel-hda: Restrict DMA engine to memories (not MMIO devices) [CVE-2021-3611]
Date: Fri, 18 Mar 2022 20:13:37 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.6.0

On 18/12/2021 17.09, Philippe Mathieu-Daudé wrote:
Issue #542 reports a reentrancy problem when the DMA engine accesses
the HDA controller I/O registers. Fix by restricting the DMA engine
to memories regions (forbidding MMIO devices such the HDA controller).

Reported-by: OSS-Fuzz (Issue 28435)
Reported-by: Alexander Bulekov <alxndr@bu.edu>
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/542
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
Likely intel_hda_xfer() and intel_hda_corb_run() should be restricted
too.
---
  hw/audio/intel-hda.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/audio/intel-hda.c b/hw/audio/intel-hda.c
index 0c1017edbbf..3aa57d274e6 100644
--- a/hw/audio/intel-hda.c
+++ b/hw/audio/intel-hda.c
@@ -345,7 +345,7 @@ static void intel_hda_corb_run(IntelHDAState *d)
static void intel_hda_response(HDACodecDevice *dev, bool solicited, uint32_t response)
  {
-    const MemTxAttrs attrs = MEMTXATTRS_UNSPECIFIED;
+    const MemTxAttrs attrs = { .memory = true };
      HDACodecBus *bus = HDA_BUS(dev->qdev.parent_bus);
      IntelHDAState *d = container_of(bus, IntelHDAState, codecs);
      hwaddr addr;

That's maybe the best we can do right now to fix CVE-2021-3611 !

Reviewed-by: Thomas Huth <thuth@redhat.com>




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