Re: [PATCH] hw/sd/sdhci: Do not modify BlockSizeRegister if transaction in progress

[Bin Meng]

Hi Philippe,

On Tue, Feb 9, 2021 at 3:34 AM Philippe Mathieu-Daudé <f4bug@amsat.org> wrote:
>
> Per the "SD Host Controller Simplified Specification Version 2.00"
> spec. 'Table 2-4 : Block Size Register':
>
>   Transfer Block Size [...] can be accessed only if no
>   transaction is executing (i.e., after a transaction has stopped).
>   Read operations during transfers may return an invalid value,
>   and write operations shall be ignored.
>
> Transactions will update 'data_count', so do not modify 'blksize'
> and 'blkcnt' when 'data_count' is used. This fixes:
>
> $ cat << EOF | qemu-system-x86_64 -qtest stdio -monitor none \
>                -nographic -serial none -M pc-q35-5.0 \
>                -device sdhci-pci,sd-spec-version=3 \
>                -device sd-card,drive=mydrive \
>                -drive if=sd,index=0,file=null-co://,format=raw,id=mydrive
>   outl 0xcf8 0x80001810
>   outl 0xcfc 0xe1068000
>   outl 0xcf8 0x80001814

Is this command needed?

>   outl 0xcf8 0x80001804
>   outw 0xcfc 0x7
>   outl 0xcf8 0x8000fa20

and this one?

>   write 0xe106802c 0x1 0x0f
>   write 0xe1068004 0xc 0x2801d10101fffffbff28a384

Are these fuzzy data?

>   write 0xe106800c 0x1f 
> 0x9dacbbcad9e8f7061524334251606f7e8d9cabbac9d8e7f60514233241505f
>   write 0xe1068003 0x28 
> 0x80d000251480d000252280d000253080d000253e80d000254c80d000255a80d000256880d0002576
>   write 0xe1068003 0x1 0xfe
>   EOF
>   =================================================================
>   ==2686219==ERROR: AddressSanitizer: heap-buffer-overflow on address 
> 0x61500003bb00 at pc 0x55ab469f456c bp 0x7ffee71be330 sp 0x7ffee71bdae0
>   WRITE of size 4 at 0x61500003bb00 thread T0
>       #0 0x55ab469f456b in __asan_memcpy (qemu-system-i386+0x1cea56b)
>       #1 0x55ab483dc396 in stl_he_p include/qemu/bswap.h:353:5
>       #2 0x55ab483af5e4 in stn_he_p include/qemu/bswap.h:546:1
>       #3 0x55ab483aeb4b in flatview_read_continue softmmu/physmem.c:2839:13
>       #4 0x55ab483b0705 in flatview_read softmmu/physmem.c:2877:12
>       #5 0x55ab483b028e in address_space_read_full softmmu/physmem.c:2890:18
>       #6 0x55ab483b1294 in address_space_rw softmmu/physmem.c:2918:16
>       #7 0x55ab479374a2 in dma_memory_rw_relaxed include/sysemu/dma.h:88:12
>       #8 0x55ab47936f50 in dma_memory_rw include/sysemu/dma.h:127:12
>       #9 0x55ab4793665f in dma_memory_read include/sysemu/dma.h:145:12
>       #10 0x55ab4792f176 in sdhci_sdma_transfer_multi_blocks 
> hw/sd/sdhci.c:639:13
>       #11 0x55ab4793dc9d in sdhci_write hw/sd/sdhci.c:1129:17
>       #12 0x55ab483f8db8 in memory_region_write_accessor 
> softmmu/memory.c:491:5
>       #13 0x55ab483f868a in access_with_adjusted_size softmmu/memory.c:552:18
>       #14 0x55ab483f6da5 in memory_region_dispatch_write 
> softmmu/memory.c:1501:16
>       #15 0x55ab483c3b11 in flatview_write_continue softmmu/physmem.c:2774:23
>       #16 0x55ab483b0eb6 in flatview_write softmmu/physmem.c:2814:14
>       #17 0x55ab483b0a3e in address_space_write softmmu/physmem.c:2906:18
>       #18 0x55ab48465c56 in qtest_process_command softmmu/qtest.c:654:9
>
>   0x61500003bb00 is located 0 bytes to the right of 512-byte region 
> [0x61500003b900,0x61500003bb00)
>   allocated by thread T0 here:
>       #0 0x55ab469f58a7 in calloc (qemu-system-i386+0x1ceb8a7)
>       #1 0x7f21d678f9b0 in g_malloc0 (/lib64/libglib-2.0.so.0+0x589b0)
>       #2 0x55ab479530ed in sdhci_pci_realize hw/sd/sdhci-pci.c:36:5
>       #3 0x55ab476f102a in pci_qdev_realize hw/pci/pci.c:2108:9
>       #4 0x55ab48baaad2 in device_set_realized hw/core/qdev.c:761:13
>
>   SUMMARY: AddressSanitizer: heap-buffer-overflow 
> (qemu-system-i386+0x1cea56b) in __asan_memcpy
>   Shadow bytes around the buggy address:
>     0x0c2a7ffff710: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
>     0x0c2a7ffff720: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>     0x0c2a7ffff730: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>     0x0c2a7ffff740: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>     0x0c2a7ffff750: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>   =>0x0c2a7ffff760:[fa]fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
>     0x0c2a7ffff770: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
>     0x0c2a7ffff780: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
>     0x0c2a7ffff790: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
>     0x0c2a7ffff7a0: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
>     0x0c2a7ffff7b0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
>   Shadow byte legend (one shadow byte represents 8 application bytes):
>     Addressable:           00
>     Heap left redzone:       fa
>     Freed heap region:       fd
>   ==2686219==ABORTING
>
> Fixes: CVE-2020-17380
> Fixes: CVE-2020-25085
> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> ---
> Cc: Mauro Matteo Cascella <mcascell@redhat.com>
> Cc: Alexander Bulekov <alxndr@bu.edu>
> Cc: Alistair Francis <alistair.francis@wdc.com>
> Cc: Prasad J Pandit <ppandit@redhat.com>
> Cc: Bandan Das <bsd@redhat.com>
>
> RFC because missing Reported-by tags, launchpad/bugzilla links and
> qtest reproducer. Sending for review meanwhile.
> ---
>  hw/sd/sdhci.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/hw/sd/sdhci.c b/hw/sd/sdhci.c
> index 8ffa53999d8..7ac7d9af9e4 100644
> --- a/hw/sd/sdhci.c
> +++ b/hw/sd/sdhci.c
> @@ -1133,6 +1133,12 @@ sdhci_write(void *opaque, hwaddr offset, uint64_t val, 
> unsigned size)
>          }
>          break;
>      case SDHC_BLKSIZE:
> +        if (s->data_count) {
> +            qemu_log_mask(LOG_GUEST_ERROR,
> +                          "%s: Can not update blksize when"
> +                          " transaction is executing\n", __func__);
> +            break;
> +        }
>          if (!TRANSFERRING_DATA(s->prnsts)) {

I am not sure I get the whole picture here.

Isn't write to s->blksize and s->blkcnt already protected in this if
() statement?

>              MASKED_WRITE(s->blksize, mask, extract32(value, 0, 12));
>              MASKED_WRITE(s->blkcnt, mask >> 16, value >> 16);
> --

Regards,
Bin