Re: [Qemu-devel] [PATCH v2] ioapic: use irq number instead of vector in ioapic_eoi_broadcast

[Peter Xu <peterx@redhat.com>]

On Fri, Jun 21, 2019 at 05:21:19PM -0700, Li Qiang wrote:
> When emulating irqchip in qemu, such as following command:
> 
> x86_64-softmmu/qemu-system-x86_64 -m 1024 -smp 4 -hda /home/test/test.img
> -machine kernel-irqchip=off --enable-kvm -vnc :0 -device edu -monitor stdio
> 
> We will get a crash with following asan output:
> 
> (qemu) /home/test/qemu5/qemu/hw/intc/ioapic.c:266:27: runtime error: index 35 out of bounds for type 'int [24]'
> =================================================================
> ==113504==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x61b000003114 at pc 0x5579e3c7a80f bp 0x7fd004bf8c10 sp 0x7fd004bf8c00
> WRITE of size 4 at 0x61b000003114 thread T4
>     #0 0x5579e3c7a80e in ioapic_eoi_broadcast /home/test/qemu5/qemu/hw/intc/ioapic.c:266
>     #1 0x5579e3c6f480 in apic_eoi /home/test/qemu5/qemu/hw/intc/apic.c:428
>     #2 0x5579e3c720a7 in apic_mem_write /home/test/qemu5/qemu/hw/intc/apic.c:802
>     #3 0x5579e3b1e31a in memory_region_write_accessor /home/test/qemu5/qemu/memory.c:503
>     #4 0x5579e3b1e6a2 in access_with_adjusted_size /home/test/qemu5/qemu/memory.c:569
>     #5 0x5579e3b28d77 in memory_region_dispatch_write /home/test/qemu5/qemu/memory.c:1497
>     #6 0x5579e3a1b36b in flatview_write_continue /home/test/qemu5/qemu/exec.c:3323
>     #7 0x5579e3a1b633 in flatview_write /home/test/qemu5/qemu/exec.c:3362
>     #8 0x5579e3a1bcb1 in address_space_write /home/test/qemu5/qemu/exec.c:3452
>     #9 0x5579e3a1bd03 in address_space_rw /home/test/qemu5/qemu/exec.c:3463
>     #10 0x5579e3b8b979 in kvm_cpu_exec /home/test/qemu5/qemu/accel/kvm/kvm-all.c:2045
>     #11 0x5579e3ae4499 in qemu_kvm_cpu_thread_fn /home/test/qemu5/qemu/cpus.c:1287
>     #12 0x5579e4cbdb9f in qemu_thread_start util/qemu-thread-posix.c:502
>     #13 0x7fd0146376da in start_thread (/lib/x86_64-linux-gnu/libpthread.so.0+0x76da)
>     #14 0x7fd01436088e in __clone (/lib/x86_64-linux-gnu/libc.so.6+0x12188e
> 
> This is because in ioapic_eoi_broadcast function, we uses 'vector' to
> index the 's->irq_eoi'. To fix this, we should uses the irq number.
> 
> Signed-off-by: Li Qiang <liq3ea@163.com>

Reviewed-by: Peter Xu <peterx@redhat.com>

Maybe also add:

Fixes: 958a01dab8 ("ioapic: allow buggy guests mishandling ...")

Should we better clear irq_eoi when the entries are updated in
ioapic_mem_write()?

Regards,

-- 
Peter Xu