On Thu, Jul 17, 2025 at 10:01:16AM +0100, Will Deacon wrote: > When transmitting a vsock packet, virtio_transport_send_pkt_info() calls > virtio_transport_alloc_linear_skb() to allocate and fill SKBs with the > transmit data. Unfortunately, these are always linear allocations and > can therefore result in significant pressure on kmalloc() considering > that the maximum packet size (VIRTIO_VSOCK_MAX_PKT_BUF_SIZE + > VIRTIO_VSOCK_SKB_HEADROOM) is a little over 64KiB, resulting in a 128KiB > allocation for each packet. > > Rework the vsock SKB allocation so that, for sizes with page order > greater than PAGE_ALLOC_COSTLY_ORDER, a nonlinear SKB is allocated > instead with the packet header in the SKB and the transmit data in the > fragments. Note that this affects both the vhost and virtio transports. > > Reviewed-by: Stefano Garzarella <sgarzare@xxxxxxxxxx> > Signed-off-by: Will Deacon <will@xxxxxxxxxx> So this caused a regression, see syzbot report: https://lore.kernel.org/all/689a3d92.050a0220.7f033.00ff.GAE@xxxxxxxxxx I'm inclined to revert unless we have a fix quickly. > --- > net/vmw_vsock/virtio_transport_common.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c > index c9eb7f7ac00d..fe92e5fa95b4 100644 > --- a/net/vmw_vsock/virtio_transport_common.c > +++ b/net/vmw_vsock/virtio_transport_common.c > @@ -109,7 +109,8 @@ static int virtio_transport_fill_skb(struct sk_buff *skb, > return __zerocopy_sg_from_iter(info->msg, NULL, skb, > &info->msg->msg_iter, len, NULL); > > - return memcpy_from_msg(skb_put(skb, len), info->msg, len); > + virtio_vsock_skb_put(skb, len); > + return skb_copy_datagram_from_iter(skb, 0, &info->msg->msg_iter, len); > } > > static void virtio_transport_init_hdr(struct sk_buff *skb, > @@ -261,7 +262,7 @@ static struct sk_buff *virtio_transport_alloc_skb(struct virtio_vsock_pkt_info * > if (!zcopy) > skb_len += payload_len; > > - skb = virtio_vsock_alloc_linear_skb(skb_len, GFP_KERNEL); > + skb = virtio_vsock_alloc_skb(skb_len, GFP_KERNEL); > if (!skb) > return NULL; > > -- > 2.50.0.727.gbf7dc18ff4-goog
