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

[Li Qiang]

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 <address@hidden>
---
Change since v1:
remove auto-generated unnecessary message

 hw/intc/ioapic.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/hw/intc/ioapic.c b/hw/intc/ioapic.c
index 7074489fdf..711775cc6f 100644
--- a/hw/intc/ioapic.c
+++ b/hw/intc/ioapic.c
@@ -245,8 +245,8 @@ void ioapic_eoi_broadcast(int vector)
             s->ioredtbl[n] = entry & ~IOAPIC_LVT_REMOTE_IRR;
 
             if (!(entry & IOAPIC_LVT_MASKED) && (s->irr & (1 << n))) {
-                ++s->irq_eoi[vector];
-                if (s->irq_eoi[vector] >= SUCCESSIVE_IRQ_MAX_COUNT) {
+                ++s->irq_eoi[n];
+                if (s->irq_eoi[n] >= SUCCESSIVE_IRQ_MAX_COUNT) {
                     /*
                      * Real hardware does not deliver the interrupt immediately
                      * during eoi broadcast, and this lets a buggy guest make
@@ -254,16 +254,16 @@ void ioapic_eoi_broadcast(int vector)
                      * level-triggered interrupt. Emulate this behavior if we
                      * detect an interrupt storm.
                      */
-                    s->irq_eoi[vector] = 0;
+                    s->irq_eoi[n] = 0;
                     timer_mod_anticipate(s->delayed_ioapic_service_timer,
                                          qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) 
+
                                          NANOSECONDS_PER_SECOND / 100);
-                    trace_ioapic_eoi_delayed_reassert(vector);
+                    trace_ioapic_eoi_delayed_reassert(n);
                 } else {
                     ioapic_service(s);
                 }
             } else {
-                s->irq_eoi[vector] = 0;
+                s->irq_eoi[n] = 0;
             }
         }
     }
-- 
2.17.1