From: Paolo Abeni pabeni@redhat.com
commit 3c4cea8fa7f71f00c5279547043a84bc2a4d8b8c upstream.
If the sendmsg() call in vhost_tx_batch() fails, both the 'batched_xdp' and 'done_idx' indexes are left unchanged. If such failure happens when batched_xdp == VHOST_NET_BATCH, the next call to vhost_net_build_xdp() will access and write memory outside the xdp buffers area.
Since sendmsg() can only error with EBADFD, this change addresses the issue explicitly freeing the XDP buffers batch on error.
Fixes: 0a0be13b8fe2 ("vhost_net: batch submitting XDP buffers to underlayer sockets") Suggested-by: Jason Wang jasowang@redhat.com Signed-off-by: Paolo Abeni pabeni@redhat.com Acked-by: Jason Wang jasowang@redhat.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/vhost/net.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-)
--- a/drivers/vhost/net.c +++ b/drivers/vhost/net.c @@ -466,7 +466,7 @@ static void vhost_tx_batch(struct vhost_ .num = nvq->batched_xdp, .ptr = nvq->xdp, }; - int err; + int i, err;
if (nvq->batched_xdp == 0) goto signal_used; @@ -475,6 +475,15 @@ static void vhost_tx_batch(struct vhost_ err = sock->ops->sendmsg(sock, msghdr, 0); if (unlikely(err < 0)) { vq_err(&nvq->vq, "Fail to batch sending packets\n"); + + /* free pages owned by XDP; since this is an unlikely error path, + * keep it simple and avoid more complex bulk update for the + * used pages + */ + for (i = 0; i < nvq->batched_xdp; ++i) + put_page(virt_to_head_page(nvq->xdp[i].data)); + nvq->batched_xdp = 0; + nvq->done_idx = 0; return; }