Re: [Qemu-devel] [PATCH 0/1] Add check for header length in virtio-net-tx

[Michael S. Tsirkin]

On Tue, Jul 16, 2019 at 03:38:00AM +0000, Oleinik, Alexander wrote:
> While fuzzing the virtio-net tx vq, I ran into an assertion failure due
> to iov_copy offsets larger than the total iov size. Though there is
> a check to cover this, it does not execute when !n->has_vnet_hdr. This
> patch tries to fix this. 
> 
> The call stack for the assertion failure:
> 
> #8 in __assert_fail (libc.so.6+0x300f1)
> #9 in iov_copy iov.c:266:5
> #10 in virtio_net_flush_tx virtio-net.c:2073:23
> #11 in virtio_net_tx_bh virtio-net.c:2197:11
> #12 in aio_bh_poll async.c:118:13
> #13 in aio_dispatch aio-posix.c:460:5
> #14 in aio_ctx_dispatch async.c:261:5
> #15 in g_main_context_dispatch (libglib-2.0.so.0+0x4df2d)
> #16 in glib_pollfds_poll main-loop.c:213:9
> #17 in os_host_main_loop_wait main-loop.c:236
> #18 in main_loop_wait main-loop.c:512
> #19 in virtio_net_tx_fuzz virtio-net-fuzz.c:160:3
> 
> Thanks
> -Alex

I think I'd rather introduce a variant of iov_copy
that returns the remaining offset.

the code that duplicates this for byte-swap seems to
also have this problem.


> Alexander Oleinik (1):
>   virtio-net: check guest header length is valid
> 
>  hw/net/virtio-net.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> -- 
> 2.20.1