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Length restrictions for fw_cfg_dma_transfer?
For me, this takes close to 3 minutes at 100% CPU:
echo "outl 0x518 0x9596ffff" | ./i386-softmmu/qemu-system-i386 -M q35 -m 32 -nographic -accel qtest -monitor none -serial none -qtest stdio
#0 phys_page_find (d=0x606000035d80, addr=136728041144404) at /exec.c:338
#1 address_space_lookup_region (d=0x606000035d80, addr=136728041144404, resolve_subpage=true) at /exec.c:363
#2 address_space_translate_internal (d=0x606000035d80, addr=136728041144404, xlat=0x7fff1fc0d070, plen=0x7fff1fc0d090, resolve_subpage=true) at /exec.c:382
#3 flatview_do_translate (fv=0x606000035d20, addr=136728041144404, xlat=0x7fff1fc0d070, plen_out=0x7fff1fc0d090, page_mask_out=0x0, is_write=true, is_mmio=true, target_as=0x7fff1fc0ce10, attrs=...)
pment/qemu/exec.c:520
#4 flatview_translate (fv=0x606000035d20, addr=136728041144404, xlat=0x7fff1fc0d070, plen=0x7fff1fc0d090, is_write=true, attrs=...) at /exec.c:586
#5 flatview_write_continue (fv=0x606000035d20, addr=136728041144404, attrs=..., ptr=0x7fff1fc0d660, len=172, addr1=136728041144400, l=172, mr=0x557fd54e77e0 <io_mem_unassigned>)
pment/qemu/exec.c:3160
#6 flatview_write (fv=0x606000035d20, addr=136728041144064, attrs=..., buf=0x7fff1fc0d660, len=512) at /exec.c:3177
#7 address_space_write (as=0x557fd54e7a00 <address_space_memory>, addr=136728041144064, attrs=..., buf=0x7fff1fc0d660, len=512) at /exec.c:3271
#8 dma_memory_set (as=0x557fd54e7a00 <address_space_memory>, addr=136728041144064, c=0 '\000', len=1378422272) at /dma-helpers.c:31
#9 fw_cfg_dma_transfer (s=0x61a000001e80) at /hw/nvram/fw_cfg.c:400
#10 fw_cfg_dma_mem_write (opaque=0x61a000001e80, addr=4, value=4294940309, size=4) at /hw/nvram/fw_cfg.c:467
#11 memory_region_write_accessor (mr=0x61a000002200, addr=4, value=0x7fff1fc0e3d0, size=4, shift=0, mask=4294967295, attrs=...) at /memory.c:483
#12 access_with_adjusted_size (addr=4, value=0x7fff1fc0e3d0, size=4, access_size_min=1, access_size_max=8, access_fn=0x557fd2288c80 <memory_region_write_accessor>, mr=0x61a000002200, attrs=...)
pment/qemu/memory.c:539
#13 memory_region_dispatch_write (mr=0x61a000002200, addr=4, data=4294940309, op=MO_32, attrs=...) at /memory.c:1476
#14 flatview_write_continue (fv=0x606000035f00, addr=1304, attrs=..., ptr=0x7fff1fc0ec40, len=4, addr1=4, l=4, mr=0x61a000002200) at /exec.c:3137
#15 flatview_write (fv=0x606000035f00, addr=1304, attrs=..., buf=0x7fff1fc0ec40, len=4) at /exec.c:3177
#16 address_space_write (as=0x557fd54e7bc0 <address_space_io>, addr=1304, attrs=..., buf=0x7fff1fc0ec40, len=4) at /exec.c:3271
It looks like fw_cfg_dma_transfer gets the address(136728041144064) and length(1378422272) for the read from the value provided as input 4294940309 (0xFFFF9695) which lands in pcbios. Should there be any limits on the length of guest-memory that fw_cfg should populate?
Found by libfuzzer
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