aarch64-virt: heap-use-after-free in gic_dist_writeb

[Alexander Bulekov]

Reproducer:
cat << EOF | ./qemu-system-aarch64 \
-machine virt,accel=qtest -qtest stdio
writel 0x8000f00 0x5affaf
write 0x8000eff 0x1 0x0
EOF

Stacktrace:
../hw/intc/arm_gic.c:1419:17: runtime error: index 3068 out of bounds for type 'gic_irq_state [1020]'
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior ../hw/intc/arm_gic.c:1419:17 in
=================================================================
==641550==ERROR: AddressSanitizer: heap-use-after-free on address 0x629000023a85 at pc 0x55b5dfb0fbf8 bp 0x7fff95cb5870 sp 0x7fff95cb5868
WRITE of size 1 at 0x629000023a85 thread T0
    #0 0x55b5dfb0fbf7 in gic_dist_writeb /home/alxndr/Development/qemu/build/../hw/intc/arm_gic.c:1419:17
    #1 0x55b5dfb061e2 in gic_dist_write /home/alxndr/Development/qemu/build/../hw/intc/arm_gic.c
    #2 0x55b5e0809ef4 in memory_region_write_with_attrs_accessor /home/alxndr/Development/qemu/build/../softmmu/memory.c:511:12
    #3 0x55b5e0808bfb in access_with_adjusted_size /home/alxndr/Development/qemu/build/../softmmu/memory.c:552:18
    #4 0x55b5e0808467 in memory_region_dispatch_write /home/alxndr/Development/qemu/build/../softmmu/memory.c
    #5 0x55b5e0b98ffb in flatview_write_continue /home/alxndr/Development/qemu/build/../softmmu/physmem.c:2759:23
    #6 0x55b5e0b8e71b in flatview_write /home/alxndr/Development/qemu/build/../softmmu/physmem.c:2799:14
    #7 0x55b5e0b8e71b in address_space_write /home/alxndr/Development/qemu/build/../softmmu/physmem.c:2891:18
    #8 0x55b5e07fad35 in qtest_process_command /home/alxndr/Development/qemu/build/../softmmu/qtest.c:654:9
    #9 0x55b5e07f3b97 in qtest_process_inbuf /home/alxndr/Development/qemu/build/../softmmu/qtest.c:797:9
    #10 0x55b5e1044286 in fd_chr_read /home/alxndr/Development/qemu/build/../chardev/char-fd.c:68:9
    #11 0x7fa997b30aae in g_main_context_dispatch (/usr/lib/x86_64-linux-gnu/libglib-2.0.so.0+0x51aae)
    #12 0x55b5e169f363 in glib_pollfds_poll /home/alxndr/Development/qemu/build/../util/main-loop.c:232:9
    #13 0x55b5e169f363 in os_host_main_loop_wait /home/alxndr/Development/qemu/build/../util/main-loop.c:255:5
    #14 0x55b5e169f363 in main_loop_wait /home/alxndr/Development/qemu/build/../util/main-loop.c:531:11
    #15 0x55b5e075a599 in qemu_main_loop /home/alxndr/Development/qemu/build/../softmmu/runstate.c:721:9
    #16 0x55b5de9e71fd in main /home/alxndr/Development/qemu/build/../softmmu/main.c:50:5
    #17 0x7fa9975d5cc9 in __libc_start_main csu/../csu/libc-start.c:308:16
    #18 0x55b5de93abc9 in _start (/home/alxndr/Development/qemu/build/qemu-system-aarch64+0x3350bc9)

[Philippe Mathieu-Daudé (philmd)]

Fix for this 13+ years old issue:
https://lists.gnu.org/archive/html/qemu-devel/2021-01/msg07969.html

[Peter Maydell (pmaydell)]

The actual overrun here is not the one the backtrace describes. The first "writel 0x8000f00 0x5affaf" writes a value to GICD_SGIR which overruns the sgi_pending array in the GICState structure. In particular, it overwrites the s->num_irq field, which is what is guarding the array access to gic_irq_state[] that the "write 0x8000eff 0x1 0x0" exercises. With the first overrun fixed, the check for "if (irq >= s->num_irq)" functions correctly.

[Philippe Mathieu-Daudé (philmd)]

Commited as edfe2eb4360cde4ed5d95bda7777edcb3510f76a.