virtio_transport_send_pkt in now called on transport fast path, under RCU read lock. In that case, we have a bug: virtio_add_sgs is called with GFP_KERNEL, and might sleep.
Pass the gfp flags as an argument, and use GFP_ATOMIC on the fast path. Link: https://lore.kernel.org/all/hfcr2aget2zojmqpr4uhlzvnep4vgskblx5b6xf2ddosbsrke7@nt34bxgp7j2x Fixes: efcd71af38be ("vsock/virtio: avoid queuing packets when intermediate queue is empty") Reported-by: Christian Brauner <brau...@kernel.org> Cc: Stefano Garzarella <sgarz...@redhat.com> Cc: Luigi Leonardi <luigi.leona...@outlook.com> Signed-off-by: Michael S. Tsirkin <m...@redhat.com> --- Lightly tested. Christian, could you pls confirm this fixes the problem for you? Stefano, it's a holiday here - could you pls help test! Thanks! net/vmw_vsock/virtio_transport.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c index f992f9a216f0..0cd965f24609 100644 --- a/net/vmw_vsock/virtio_transport.c +++ b/net/vmw_vsock/virtio_transport.c @@ -96,7 +96,7 @@ static u32 virtio_transport_get_local_cid(void) /* Caller need to hold vsock->tx_lock on vq */ static int virtio_transport_send_skb(struct sk_buff *skb, struct virtqueue *vq, - struct virtio_vsock *vsock) + struct virtio_vsock *vsock, gfp_t gfp) { int ret, in_sg = 0, out_sg = 0; struct scatterlist **sgs; @@ -140,7 +140,7 @@ static int virtio_transport_send_skb(struct sk_buff *skb, struct virtqueue *vq, } } - ret = virtqueue_add_sgs(vq, sgs, out_sg, in_sg, skb, GFP_KERNEL); + ret = virtqueue_add_sgs(vq, sgs, out_sg, in_sg, skb, gfp); /* Usually this means that there is no more space available in * the vq */ @@ -178,7 +178,7 @@ virtio_transport_send_pkt_work(struct work_struct *work) reply = virtio_vsock_skb_reply(skb); - ret = virtio_transport_send_skb(skb, vq, vsock); + ret = virtio_transport_send_skb(skb, vq, vsock, GFP_KERNEL); if (ret < 0) { virtio_vsock_skb_queue_head(&vsock->send_pkt_queue, skb); break; @@ -221,7 +221,7 @@ static int virtio_transport_send_skb_fast_path(struct virtio_vsock *vsock, struc if (unlikely(ret == 0)) return -EBUSY; - ret = virtio_transport_send_skb(skb, vq, vsock); + ret = virtio_transport_send_skb(skb, vq, vsock, GFP_ATOMIC); if (ret == 0) virtqueue_kick(vq); -- MST
