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[RFC PATCH v2 0/5] physmem: Have flaview API check bus permission from M


From: Philippe Mathieu-Daudé
Subject: [RFC PATCH v2 0/5] physmem: Have flaview API check bus permission from MemTxAttrs argument
Date: Mon, 23 Aug 2021 18:41:52 +0200

This series aim to kill a recent class of bug, the infamous
"DMA reentrancy" issues found by Alexander while fuzzing.

Introduce the 'bus_perm' field in MemTxAttrs, defining 3 bits:

- MEMTXPERM_UNSPECIFIED (current default, unchanged behavior)
- MEMTXPERM_UNRESTRICTED (allow list approach)
- MEMTXPERM_RAM_DEVICE (example of deny list approach)

If a transaction permission is not allowed (for example access
to non-RAM device), we return the specific MEMTX_BUS_ERROR.

Permissions are checked in after the flatview is resolved, and
before the access is done, in a new function: flatview_access_allowed().

I'll post another series on top as example, fixing the SD card
bugs.

Since v1 ("hw: Forbid DMA write accesses to MMIO regions") [1]:
- rewrite based on Peter / Stefan feedbacks

Based on "hw: Let the DMA API take a MemTxAttrs argument" [2].

Supersedes: <20200903110831.353476-1-philmd@redhat.com>
Based-on: <20210702092439.989969-1-philmd@redhat.com>

[1] https://www.mail-archive.com/qemu-block@nongnu.org/msg72924.html
[2] https://www.mail-archive.com/qemu-devel@nongnu.org/msg820359.html

Philippe Mathieu-Daudé (5):
  softmmu/physmem: Simplify flatview_write and
    address_space_access_valid
  hw/intc/arm_gicv3: Check for !MEMTX_OK instead of MEMTX_ERROR
  exec/memattrs: Introduce MemTxAttrs::bus_perm field
  softmmu/physmem: Introduce flatview_access_allowed() to check bus
    perms
  softmmu/physmem: Have flaview API check MemTxAttrs::bus_perm field

 include/exec/memattrs.h    | 21 +++++++++++++
 hw/intc/arm_gicv3_dist.c   |  4 +--
 hw/intc/arm_gicv3_redist.c |  4 +--
 softmmu/physmem.c          | 61 ++++++++++++++++++++++++++++++++------
 4 files changed, 77 insertions(+), 13 deletions(-)

-- 
2.31.1





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