hw/virtio.c checks vq->vring.desc != NULL to see if the vring has been
set up successfully.
When virtio_queue_set_rings() fails due to an invalid vring memory
address it must clear vq->vring.desc (and related fields) so we don't
treat this virtqueue as successfully initialized later on.
This bug was found by device fuzzing and can be triggered as follows:
$ qemu -M pc -device virtio-blk-pci,id=drv0,drive=drive0,addr=4.0 \
-drive if=none,id=drive0,file=null-co://,format=raw,auto-read-only=off
\
-drive
if=none,id=drive1,file=null-co://,file.read-zeroes=on,format=raw \
-display none \
-qtest stdio
endianness
outl 0xcf8 0x80002020
outl 0xcfc 0xe0000000
outl 0xcf8 0x80002004
outw 0xcfc 0x7
write 0xe0000000 0x24
0x00ffffffabffffffabffffffabffffffabffffffabffffffabffffffabffffffabffffffabffffffabffffffabffffffabffffffabffffffab5cffffffabffffffabffffffabffffffabffffffabffffffabffffffabffffffabffffffabffffffabffffffabffffffabffffffabffffffabffffffab0000000001
inb 0x4
writew 0xe000001c 0x1
write 0xe0000014 0x1 0x0d
The following error message is produced:
qemu-system-x86_64: /home/stefanha/qemu/hw/virtio/virtio.c:286:
vring_get_region_caches: Assertion `caches != NULL' failed.
The backtrace looks like this:
#0 0x00007ffff5520625 in raise () at /lib64/libc.so.6
#1 0x00007ffff55098d9 in abort () at /lib64/libc.so.6
#2 0x00007ffff55097a9 in _nl_load_domain.cold () at /lib64/libc.so.6
#3 0x00007ffff5518a66 in annobin_assert.c_end () at /lib64/libc.so.6
#4 0x00005555559073da in vring_get_region_caches (vq=<optimized out>) at
qemu/hw/virtio/virtio.c:286
#5 vring_get_region_caches (vq=<optimized out>) at
qemu/hw/virtio/virtio.c:283
#6 0x000055555590818d in vring_used_flags_set_bit (mask=1,
vq=0x5555575ceea0) at qemu/hw/virtio/virtio.c:398
#7 virtio_queue_split_set_notification (enable=0, vq=0x5555575ceea0) at
qemu/hw/virtio/virtio.c:398
#8 virtio_queue_set_notification (vq=vq@entry=0x5555575ceea0,
enable=enable@entry=0) at qemu/hw/virtio/virtio.c:451
#9 0x0000555555908512 in virtio_queue_set_notification
(vq=vq@entry=0x5555575ceea0, enable=enable@entry=0) at
qemu/hw/virtio/virtio.c:444
#10 0x00005555558c697a in virtio_blk_handle_vq (s=0x5555575c57e0,
vq=0x5555575ceea0) at qemu/hw/block/virtio-blk.c:775
#11 0x0000555555907836 in virtio_queue_notify_aio_vq (vq=0x5555575ceea0) at
qemu/hw/virtio/virtio.c:2244
#12 0x0000555555cb5dd7 in aio_dispatch_handlers
(ctx=ctx@entry=0x55555671a420) at util/aio-posix.c:429
#13 0x0000555555cb67a8 in aio_dispatch (ctx=0x55555671a420) at
util/aio-posix.c:460
#14 0x0000555555cb307e in aio_ctx_dispatch (source=<optimized out>,
callback=<optimized out>, user_data=<optimized out>) at util/async.c:260
#15 0x00007ffff7bbc510 in g_main_context_dispatch () at
/lib64/libglib-2.0.so.0
#16 0x0000555555cb5848 in glib_pollfds_poll () at util/main-loop.c:219
#17 os_host_main_loop_wait (timeout=<optimized out>) at util/main-loop.c:242
#18 main_loop_wait (nonblocking=<optimized out>) at util/main-loop.c:518
#19 0x00005555559b20c9 in main_loop () at vl.c:1683
#20 0x0000555555838115 in main (argc=<optimized out>, argv=<optimized out>,
envp=<optimized out>) at vl.c:4441
Reported-by: Alexander Bulekov <alx...@bu.edu>
Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
---
hw/virtio/virtio.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 2c5410e981..5d7f619a1e 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -2163,6 +2163,11 @@ void virtio_queue_set_rings(VirtIODevice *vdev, int n,
hwaddr desc,
vdev->vq[n].vring.avail = avail;
vdev->vq[n].vring.used = used;
virtio_init_region_cache(vdev, n);
+ if (vdev->broken) {
+ vdev->vq[n].vring.desc = 0;
+ vdev->vq[n].vring.avail = 0;
+ vdev->vq[n].vring.used = 0;
+ }
}
void virtio_queue_set_num(VirtIODevice *vdev, int n, int num)
--
2.24.1
