The issue reported by OSS-Fuzz produces the following backtrace:

  ==447470==ERROR: AddressSanitizer: heap-buffer-overflow
  READ of size 1 at 0x61500002a080 thread T0
      #0 0x71766d47 in sdhci_read_dataport hw/sd/sdhci.c:474:18
      #1 0x7175f139 in sdhci_read hw/sd/sdhci.c:1022:19
      #2 0x721b937b in memory_region_read_accessor softmmu/memory.c:440:11
      #3 0x72171e51 in access_with_adjusted_size softmmu/memory.c:554:18
      #4 0x7216f47c in memory_region_dispatch_read1 softmmu/memory.c:1424:16
      #5 0x7216ebb9 in memory_region_dispatch_read softmmu/memory.c:1452:9
      #6 0x7212db5d in flatview_read_continue softmmu/physmem.c:2879:23
      #7 0x7212f958 in flatview_read softmmu/physmem.c:2921:12
      #8 0x7212f418 in address_space_read_full softmmu/physmem.c:2934:18
      #9 0x721305a9 in address_space_rw softmmu/physmem.c:2962:16
      #10 0x7175a392 in dma_memory_rw_relaxed include/sysemu/dma.h:89:12
      #11 0x7175a0ea in dma_memory_rw include/sysemu/dma.h:132:12
      #12 0x71759684 in dma_memory_read include/sysemu/dma.h:152:12
      #13 0x7175518c in sdhci_do_adma hw/sd/sdhci.c:823:27
      #14 0x7174bf69 in sdhci_data_transfer hw/sd/sdhci.c:935:13
      #15 0x7176aaa7 in sdhci_send_command hw/sd/sdhci.c:376:9
      #16 0x717629ee in sdhci_write hw/sd/sdhci.c:1212:9
      #17 0x72172513 in memory_region_write_accessor softmmu/memory.c:492:5
      #18 0x72171e51 in access_with_adjusted_size softmmu/memory.c:554:18
      #19 0x72170766 in memory_region_dispatch_write softmmu/memory.c:1504:16
      #20 0x721419ee in flatview_write_continue softmmu/physmem.c:2812:23
      #21 0x721301eb in flatview_write softmmu/physmem.c:2854:12
      #22 0x7212fca8 in address_space_write softmmu/physmem.c:2950:18
      #23 0x721d9a53 in qtest_process_command softmmu/qtest.c:727:9

A DMA descriptor is previously filled in RAM. An I/O access to the
device (frames #22 to #16) start the DMA engine (frame #13). The
engine fetch the descriptor and execute the request, which itself
accesses the SDHCI I/O registers (frame #1 and #0), triggering a
re-entrancy issue.

Fix by prohibit transactions from the DMA to devices. The DMA engine
is thus restricted to memories.

Reported-by: OSS-Fuzz (Issue 36391)
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/451


Message-Id: <20211215205656.488940-3-philmd@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>