Re: [PATCH v2 6/6] hw/sd: sdhci: Reset the data pointer of s->fifo_buffer[] when a different block size is programmed

[Philippe Mathieu-Daudé]

Hi Bin,

On 2/16/21 4:46 AM, Bin Meng wrote:
> If the block size is programmed to a different value from the
> previous one, reset the data pointer of s->fifo_buffer[] so that
> s->fifo_buffer[] can be filled in using the new block size in
> the next transfer.
> 
> With this fix, the following reproducer:
> 
> outl 0xcf8 0x80001010
> outl 0xcfc 0xe0000000
> outl 0xcf8 0x80001001
> outl 0xcfc 0x06000000
> write 0xe000002c 0x1 0x05
> write 0xe0000005 0x1 0x02
> write 0xe0000007 0x1 0x01
> write 0xe0000028 0x1 0x10
> write 0x0 0x1 0x23
> write 0x2 0x1 0x08
> write 0xe000000c 0x1 0x01
> write 0xe000000e 0x1 0x20
> write 0xe000000f 0x1 0x00
> write 0xe000000c 0x1 0x32
> write 0xe0000004 0x2 0x0200
> write 0xe0000028 0x1 0x00
> write 0xe0000003 0x1 0x40
> 
> cannot be reproduced with the following QEMU command line:
> 
> $ qemu-system-x86_64 -nographic -machine accel=qtest -m 512M \
>       -nodefaults -device sdhci-pci,sd-spec-version=3 \
>       -drive if=sd,index=0,file=null-co://,format=raw,id=mydrive \
>       -device sd-card,drive=mydrive -qtest stdio
> 
> Cc: qemu-stable@nongnu.org
> Fixes: CVE-2020-17380
> Fixes: CVE-2020-25085
> Fixes: CVE-2021-3409
> Fixes: d7dfca0807a0 ("hw/sdhci: introduce standard SD host controller")
> Reported-by: Alexander Bulekov <alxndr@bu.edu>
> Reported-by: Cornelius Aschermann (Ruhr-University Bochum)
> Reported-by: Muhammad Ramdhan
> Reported-by: Sergej Schumilo (Ruhr-University Bochum)
> Reported-by: Simon Wrner (Ruhr-University Bochum)
> Buglink: https://bugs.launchpad.net/qemu/+bug/1892960
> Buglink: https://bugs.launchpad.net/qemu/+bug/1909418
> Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1928146
> Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
> 
> ---
> 
> Changes in v2:
> - new patch: sdhci: Reset the data pointer of s->fifo_buffer[] when a 
> different block size is programmed
> 
>  hw/sd/sdhci.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/hw/sd/sdhci.c b/hw/sd/sdhci.c
> index d0c8e29..5b86781 100644
> --- a/hw/sd/sdhci.c
> +++ b/hw/sd/sdhci.c
> @@ -1140,6 +1140,8 @@ sdhci_write(void *opaque, hwaddr offset, uint64_t val, 
> unsigned size)
>          break;
>      case SDHC_BLKSIZE:
>          if (!TRANSFERRING_DATA(s->prnsts)) {
> +            uint16_t blksize = s->blksize;
> +
>              MASKED_WRITE(s->blksize, mask, extract32(value, 0, 12));
>              MASKED_WRITE(s->blkcnt, mask >> 16, value >> 16);
>  
> @@ -1151,6 +1153,16 @@ sdhci_write(void *opaque, hwaddr offset, uint64_t val, 
> unsigned size)
>  
>                  s->blksize = deposit32(s->blksize, 0, 12, s->buf_maxsz);
>              }
> +
> +            /*
> +             * If the block size is programmed to a different value from
> +             * the previous one, reset the data pointer of s->fifo_buffer[]
> +             * so that s->fifo_buffer[] can be filled in using the new block
> +             * size in the next transfer.
> +             */
> +            if (blksize != s->blksize) {
> +                s->data_count = 0;

I doubt the hardware works that way. Shouldn't we reset the FIFO
each time BLKSIZE is accessed, regardless of its previous value?

> +            }
>          }
>  
>          break;
>