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Re: [PATCH v4 for-6.0 00/12] esp: fix asserts/segfaults discovered by fu

From: Mark Cave-Ayland
Subject: Re: [PATCH v4 for-6.0 00/12] esp: fix asserts/segfaults discovered by fuzzer
Date: Fri, 9 Apr 2021 12:39:33 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.9.0

On 07/04/2021 20:57, Mark Cave-Ayland wrote:

(added Peter to CC)

Recently there have been a number of issues raised on Launchpad as a result of
fuzzing the am53c974 (ESP) device. I spent some time over the past couple of
days checking to see if anything had improved since my last patchset: from
what I can tell the issues are still present, but the cmdfifo related failures
now assert rather than corrupting memory.

This patchset applied to master passes my local tests using the qtest fuzz test
cases added by Alexander for the following Launchpad bugs:

I'm posting this now just before soft freeze since I see that some of the issues
have recently been allocated CVEs and so it could be argued that even though
they have existed for some time, it is worth fixing them for 6.0.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>

- Rebase onto master
- Add R-B tags from Phil
- Fix accidental line space removal in patch 3 discovered by Phil
- Change spelling of sanitiser -> sanitizer in patch 5 as suggested by Phil
- Fix up cmdfifo length checks in patch 8
- Add T-B tags from Alex
- Add patch 11 to handle additional assert discovered by Alex during fuzzing

- Rebase onto master
- Rearrange patch ordering (move patch 5 to the front) to help reduce cross-talk
   between the regression tests
- Introduce patch 2 to remove unnecessary FIFO usage
- Introduce patches 3-4 to consolidate esp_fifo_pop()/esp_fifo_push() wrapper
   functions to avoid having to introduce 2 variants of esp_fifo_pop_buf()
- Introduce esp_fifo_pop_buf() in patch 5 to prevent callers from overflowing
   the array used to model the FIFO
- Introduce patch 10 to clarify cancellation logic should all occur in the 
   SCSI callback rather than at the site of the caller
- Add extra qtests in patch 11 to cover addition test cases provided on LP

- Add Alexander's R-B tag for patch 2 and Phil's R-B for patch 3
- Add patch 4 for additional testcase provided in Alexander's patch 1 comment
- Move current_req NULL checks forward in DMA functions (fixes ASAN bug reported
   at https://bugs.launchpad.net/qemu/+bug/1909247/comments/6) in patch 3
- Add qtest for am53c974 containing a basic set of regression tests using the
   automatic test cases generated by the fuzzer as requested by Paolo

Mark Cave-Ayland (12):
   esp: always check current_req is not NULL before use in DMA callbacks
   esp: rework write_response() to avoid using the FIFO for DMA
   esp: consolidate esp_cmdfifo_push() into esp_fifo_push()
   esp: consolidate esp_cmdfifo_pop() into esp_fifo_pop()
   esp: introduce esp_fifo_pop_buf() and use it instead of
   esp: ensure cmdfifo is not empty and current_dev is non-NULL
   esp: don't underflow cmdfifo in do_cmd()
   esp: don't overflow cmdfifo in get_cmd()
   esp: don't overflow cmdfifo if TC is larger than the cmdfifo size
   esp: don't reset async_len directly in esp_select() if cancelling
   esp: ensure that do_cmd is set to zero before submitting an ESP select
   tests/qtest: add tests for am53c974 device

  MAINTAINERS                 |   1 +
  hw/scsi/esp.c               | 119 +++++++++++---------
  tests/qtest/am53c974-test.c | 216 ++++++++++++++++++++++++++++++++++++
  tests/qtest/meson.build     |   1 +
  4 files changed, 285 insertions(+), 52 deletions(-)
  create mode 100644 tests/qtest/am53c974-test.c

Hi Paolo,

Is this still a candidate for 6.0 as you suggested in your response to v1? There is also the related ESP fix for the SPARC acceptance test failure which I think is also appropriate for 6.0.

If so, who would be able to review/merge both these ESP patches? Given that we're already at -rc2 I'm aware that it's getting quite close to the 6.0 release.



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