On Tue, Jan 08, 2019 at 04:07:03PM +0800, Zha Bin wrote:
> The vsock core only supports 32bit CID, but the Virtio-vsock spec define
> CID (dst_cid and src_cid) as u64 and the upper 32bits is reserved as
> zero. This inconsistency causes one bug in vhost vsock driver. The
> scenarios is:
>
> 0. A hash table (vhost_vsock_hash) is used to map an CID to a vsock
> object. And hash_min() is used to compute the hash key. hash_min() is
> defined as:
> (sizeof(val) <= 4 ? hash_32(val, bits) : hash_long(val, bits)).
> That means the hash algorithm has dependency on the size of macro
> argument 'val'.
> 0. In function vhost_vsock_set_cid(), a 64bit CID is passed to
> hash_min() to compute the hash key when inserting a vsock object into
> the hash table.
> 0. In function vhost_vsock_get(), a 32bit CID is passed to hash_min()
> to compute the hash key when looking up a vsock for an CID.
>
> Because the different size of the CID, hash_min() returns different hash
> key, thus fails to look up the vsock object for an CID.
>
> To fix this bug, we keep CID as u64 in the IOCTLs and virtio message
> headers, but explicitly convert u64 to u32 when deal with the hash table
> and vsock core.
>
> Fixes: 834e772c8db0 ("vhost/vsock: fix use-after-free in network stack callers")
> Link: https://github.com/stefanha/virtio/blob/vsock/trunk/content.tex
> Signed-off-by: Zha Bin <zhabin@xxxxxxxxxxxxxxxxx>
> Reviewed-by: Liu Jiang <gerry@xxxxxxxxxxxxxxxxx>
> ---
> drivers/vhost/vsock.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
Thanks for tracking this down!
Reviewed-by: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
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