Hang with high CPU usage in sdhci_data_transfer Hello, While fuzzing, I found an input that causes QEMU to hang with 100% CPU usage. I have waited several minutes, and QEMU is still unresponsive. Using gdb, It appears that it is stuck in an sdhci_data_transfer: #0 memory_region_access_valid (mr=, addr=0x10284920, size=, is_write=0xff, attrs=...) at /home/alxndr/Development/qemu/memory.c:1378 #1 memory_region_dispatch_write (mr=, addr=, data=, op=MO_32, attrs=...) at /home/alxndr/Development/qemu/memory.c:1463 #2 flatview_write_continue (fv=, addr=0x10284920, attrs=..., ptr=, len=0xb7, addr1=0x5555582798e0, l=, mr=0x5555582798e0 ) at /home/alxndr/Development/qemu/exec.c:3137 #3 flatview_write (fv=0x606000045da0, addr=, attrs=..., buf=, len=) at /home/alxndr/Development/qemu/exec.c:3177 #4 address_space_write (as=, addr=, attrs=..., buf=0xaaaab04f325, len=0x4) at /home/alxndr/Development/qemu/exec.c:3268 #5 address_space_rw (as=0x5555572509ac , addr=0x5555582798e0, attrs=..., attrs@entry=..., buf=0xaaaab04f325, len=0x4, is_write=0xb8, is_write@entry=0x1) at /home/alxndr/Development/qemu/exec.c:3278 #6 dma_memory_rw_relaxed (as=0x5555572509ac , addr=0x5555582798e0, buf=0xaaaab04f325, len=0x4, dir=DMA_DIRECTION_FROM_DEVICE) at /home/alxndr/Development/qemu/include/sysemu/dma.h:87 #7 dma_memory_rw (as=0x5555572509ac , addr=0x5555582798e0, buf=0xaaaab04f325, len=0x4, dir=DMA_DIRECTION_FROM_DEVICE) at /home/alxndr/Development/qemu/include/sysemu/dma.h:110 #8 dma_memory_write (as=0x5555572509ac , addr=0x5555582798e0, buf=0xaaaab04f325, len=0x4) at /home/alxndr/Development/qemu/include/sysemu/dma.h:122 #9 sdhci_sdma_transfer_multi_blocks (s=) at /home/alxndr/Development/qemu/hw/sd/sdhci.c:618 #10 sdhci_data_transfer (opaque=0x61e000021080) at /home/alxndr/Development/qemu/hw/sd/sdhci.c:891 #11 sdhci_send_command (s=0x61e000021080) at /home/alxndr/Development/qemu/hw/sd/sdhci.c:364 #12 sdhci_write (opaque=, offset=0xc, val=, size=) at /home/alxndr/Development/qemu/hw/sd/sdhci.c:1158 #13 memory_region_write_accessor (mr=, addr=, value=, size=, shift=, mask=, attrs=...) at /home/alxndr/Development/qemu/memory.c:483 #14 access_with_adjusted_size (addr=, value=, size=, access_size_min=, access_size_max=, access_fn=, mr=0x61e0000219f0, attrs=...) at /home/alxndr/Development/qemu/memory.c:544 #15 memory_region_dispatch_write (mr=, addr=, data=0x1ffe0ff, op=, attrs=...) at /home/alxndr/Development/qemu/memory.c:1476 #16 flatview_write_continue (fv=, addr=0xe106800c, attrs=..., ptr=, len=0xff3, addr1=0x5555582798e0, l=, mr=0x61e0000219f0) at /home/alxndr/Development/qemu/exec.c:3137 #17 flatview_write (fv=0x606000045da0, addr=, attrs=..., buf=, len=) at /home/alxndr/Development/qemu/exec.c:3177 #18 address_space_write (as=, addr=, attrs=..., attrs@entry=..., buf=0xaaaab04f325, buf@entry=0x62100008ad00, len=0x4) at /home/alxndr/Development/qemu/exec.c:3268 #19 qtest_process_command (chr=, chr@entry=0x55555827c040 , words=) at /home/alxndr/Development/qemu/qtest.c:567 #20 qtest_process_inbuf (chr=0x55555827c040 , inbuf=0x61900000f640) at /home/alxndr/Development/qemu/qtest.c:710 I am attaching the qtest commands for reproducing it. I can reproduce it in a qemu 5.0 build using: qemu-system-i386 -M pc-q35-5.0 -qtest stdio -device sdhci-pci,sd-spec-version=3 -device sd-card,drive=mydrive -drive if=sd,index=0,file=null-co://,format=raw,id=mydrive -nographic -nographic -serial none -monitor none < attachment Please let me know if I can provide any further info. -Alex