On Tue, Feb 04, 2020 at 03:16:18PM +0000, Stefan Hajnoczi wrote:
> 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>
Fixes: ???
> ---
> 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
