The bug is an uninitialized memory read, along the translate_fail path, which results in garbage being read from iotlb_to_section, which can lead to a crash in io_readx/io_writex.
The bug may be fixed by writing any value with zero in ~TARGET_PAGE_MASK, so that the call to iotlb_to_section using the xlat'ed address returns io_mem_unassigned, as desired by the translate_fail path. It is most useful to record the original physical page address, which will eventually be logged by memory_region_access_valid when the access is rejected by unassigned_mem_accepts. Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1065 Signed-off-by: Richard Henderson <[email protected]> --- softmmu/physmem.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/softmmu/physmem.c b/softmmu/physmem.c index 657841eed0..fb0f0709b5 100644 --- a/softmmu/physmem.c +++ b/softmmu/physmem.c @@ -681,6 +681,9 @@ address_space_translate_for_iotlb(CPUState *cpu, int asidx, hwaddr addr, AddressSpaceDispatch *d = qatomic_rcu_read(&cpu->cpu_ases[asidx].memory_dispatch); + /* Record the original phys page for use by the translate_fail path. */ + *xlat = addr; + for (;;) { section = address_space_translate_internal(d, addr, &addr, plen, false); -- 2.34.1
