[PULL 2/3] hw/sd/sdhci: Do not set Buf Wr Ena before writing block (CVE-2022-3872)

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

When sdhci_write_block_to_card() is called to transfer data from
the FIFO to the SD bus, the data is already present in the buffer
and we have to consume it directly.

See the description of the 'Buffer Write Enable' bit from the
'Present State' register (prnsts::SDHC_SPACE_AVAILABLE) in Table
2.14 from the SDHCI spec v2:

  Buffer Write Enable

  This status is used for non-DMA write transfers.

  The Host Controller can implement multiple buffers to transfer
  data efficiently. This read only flag indicates if space is
  available for write data. If this bit is 1, data can be written
  to the buffer. A change of this bit from 1 to 0 occurs when all
  the block data is written to the buffer. A change of this bit
  from 0 to 1 occurs when top of block data can be written to the
  buffer and generates the Buffer Write Ready interrupt.

In our case, we do not want to overwrite the buffer, so we want
this bit to be 0, then set it to 1 once the data is written onto
the bus.

This is probably a copy/paste error from commit d7dfca0807
("hw/sdhci: introduce standard SD host controller").

OSS-Fuzz Report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=45986#c4

Reproducers:

  $ cat << EOF | \
     qemu-system-x86_64 -nodefaults -display none -machine accel=qtest \
       -m 512M  -device sdhci-pci -device sd-card,drive=mydrive \
       -drive if=none,index=0,file=null-co://,format=raw,id=mydrive \
       -nographic -qtest stdio
  outl 0xcf8 0x80001010
  outl 0xcfc 0xe0000000
  outl 0xcf8 0x80001001
  outl 0xcfc 0x06000000
  write 0xe0000058 0x1 0x6e
  write 0xe0000059 0x1 0x5a
  write 0xe0000028 0x1 0x10
  write 0xe000002c 0x1 0x05
  write 0x5a6e 0x1 0x21
  write 0x5a75 0x1 0x20
  write 0xe0000005 0x1 0x02
  write 0xe000000c 0x1 0x01
  write 0xe000000e 0x1 0x20
  write 0xe000000f 0x1 0x00
  write 0xe000000c 0x1 0x00
  write 0xe0000020 0x1 0x00
  EOF

or https://lore.kernel.org/qemu-devel/CAA8xKjXrmS0fkr28AKvNNpyAtM0y0B+5FichpsrhD+mUgnuyKg@mail.gmail.com/

Fixes: CVE-2022-3872
Reported-by: RivenDell <XRivenDell@outlook.com>
Reported-by: Siqi Chen <coc.cyqh@gmail.com>
Reported-by: ningqiang <ningqiang1@huawei.com>
Reported-by: ClusterFuzz
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Tested-by: Mauro Matteo Cascella <mcascell@redhat.com>
Message-Id: <20221107221236.47841-2-philmd@linaro.org>
---
 hw/sd/sdhci.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/sd/sdhci.c b/hw/sd/sdhci.c
index 306070c872..f230e7475f 100644
--- a/hw/sd/sdhci.c
+++ b/hw/sd/sdhci.c
@@ -954,7 +954,7 @@ static void sdhci_data_transfer(void *opaque)
             sdhci_read_block_from_card(s);
         } else {
             s->prnsts |= SDHC_DOING_WRITE | SDHC_DAT_LINE_ACTIVE |
-                    SDHC_SPACE_AVAILABLE | SDHC_DATA_INHIBIT;
+                                           SDHC_DATA_INHIBIT;
             sdhci_write_block_to_card(s);
         }
     }
-- 
2.38.1