[PATCH net-next v4 31/33] bpf: add xdp.frame_sz in bpf_prog_test_run_xdp().

Jesper Dangaard Brouer
2020-05-14T10:51:51Z

Update the memory requirements, when adding xdp.frame_sz in BPF test_run
function bpf_prog_test_run_xdp() which e.g. is used by XDP selftests.

Specifically add the expected reserved tailroom, but also allocated a
larger memory area to reflect that XDP frames usually comes in this
format. Limit the provided packet data size to 4096 minus headroom +
tailroom, as this also reflect a common 3520 bytes MTU limit with XDP.

Note that bpf_test_init already use a memory allocation method that clears
memory. Thus, this already guards against leaking uninit kernel memory.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
net/bpf/test_run.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index 29dbdd4c29f6..30ba7d38941d 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -470,25 +470,34 @@ int bpf_prog_test_run_skb(struct bpf_prog *prog, const union bpf_attr *kattr,
int bpf_prog_test_run_xdp(struct bpf_prog *prog, const union bpf_attr *kattr,
union bpf_attr __user *uattr)
{
+ u32 tailroom = SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
+ u32 headroom = XDP_PACKET_HEADROOM;
u32 size = kattr->test.data_size_in;
u32 repeat = kattr->test.repeat;
struct netdev_rx_queue *rxqueue;
struct xdp_buff xdp = {};
u32 retval, duration;
+ u32 max_data_sz;
void *data;
int ret;

if (kattr->test.ctx_in || kattr->test.ctx_out)
return -EINVAL;

- data = bpf_test_init(kattr, size, XDP_PACKET_HEADROOM + NET_IP_ALIGN, 0);
+ /* XDP have extra tailroom as (most) drivers use full page */
+ max_data_sz = 4096 - headroom - tailroom;
+ if (size > max_data_sz)
+ return -EINVAL;
+
+ data = bpf_test_init(kattr, max_data_sz, headroom, tailroom);
if (IS_ERR(data))
return PTR_ERR(data);

xdp.data_hard_start = data;
- xdp.data = data + XDP_PACKET_HEADROOM + NET_IP_ALIGN;
+ xdp.data = data + headroom;
xdp.data_meta = xdp.data;
xdp.data_end = xdp.data + size;
+ xdp.frame_sz = headroom + max_data_sz + tailroom;

rxqueue = __netif_get_rx_queue(current->nsproxy->net_ns->loopback_dev, 0);
xdp.rxq = &rxqueue->xdp_rxq;
@@ -496,8 +505,7 @@ int bpf_prog_test_run_xdp(struct bpf_prog *prog, const union bpf_attr *kattr,
ret = bpf_test_run(prog, &xdp, repeat, &retval, &duration, true);
if (ret)
goto out;
- if (xdp.data != data + XDP_PACKET_HEADROOM + NET_IP_ALIGN ||
- xdp.data_end != xdp.data + size)
+ if (xdp.data != data + headroom || xdp.data_end != xdp.data + size)
size = xdp.data_end - xdp.data;
ret = bpf_test_finish(kattr, uattr, xdp.data, size, retval, duration);