summaryrefslogtreecommitdiff
path: root/drivers/net/veth.c
diff options
context:
space:
mode:
authorJesper Dangaard Brouer <brouer@redhat.com>2020-05-14 13:49:43 +0300
committerAlexei Starovoitov <ast@kernel.org>2020-05-15 07:21:54 +0300
commit5c8572251fabc5bb49fd623c064e95a9daf6a3e3 (patch)
treeaf0d8d251053e850131e18b69960540f1188be58 /drivers/net/veth.c
parentdb612f749e2454c506f20155bba2871f0307d133 (diff)
downloadlinux-5c8572251fabc5bb49fd623c064e95a9daf6a3e3.tar.xz
veth: Adjust hard_start offset on redirect XDP frames
When native XDP redirect into a veth device, the frame arrives in the xdp_frame structure. It is then processed in veth_xdp_rcv_one(), which can run a new XDP bpf_prog on the packet. Doing so requires converting xdp_frame to xdp_buff, but the tricky part is that xdp_frame memory area is located in the top (data_hard_start) memory area that xdp_buff will point into. The current code tried to protect the xdp_frame area, by assigning xdp_buff.data_hard_start past this memory. This results in 32 bytes less headroom to expand into via BPF-helper bpf_xdp_adjust_head(). This protect step is actually not needed, because BPF-helper bpf_xdp_adjust_head() already reserve this area, and don't allow BPF-prog to expand into it. Thus, it is safe to point data_hard_start directly at xdp_frame memory area. Fixes: 9fc8d518d9d5 ("veth: Handle xdp_frames in xdp napi ring") Reported-by: Mao Wenan <maowenan@huawei.com> Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Toshiaki Makita <toshiaki.makita1@gmail.com> Acked-by: Toke Høiland-Jørgensen <toke@redhat.com> Link: https://lore.kernel.org/bpf/158945338331.97035.5923525383710752178.stgit@firesoul
Diffstat (limited to 'drivers/net/veth.c')
-rw-r--r--drivers/net/veth.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/drivers/net/veth.c b/drivers/net/veth.c
index aece0e5eec8c..d5691bb84448 100644
--- a/drivers/net/veth.c
+++ b/drivers/net/veth.c
@@ -564,13 +564,15 @@ static struct sk_buff *veth_xdp_rcv_one(struct veth_rq *rq,
struct veth_stats *stats)
{
void *hard_start = frame->data - frame->headroom;
- void *head = hard_start - sizeof(struct xdp_frame);
int len = frame->len, delta = 0;
struct xdp_frame orig_frame;
struct bpf_prog *xdp_prog;
unsigned int headroom;
struct sk_buff *skb;
+ /* bpf_xdp_adjust_head() assures BPF cannot access xdp_frame area */
+ hard_start -= sizeof(struct xdp_frame);
+
rcu_read_lock();
xdp_prog = rcu_dereference(rq->xdp_prog);
if (likely(xdp_prog)) {
@@ -592,7 +594,6 @@ static struct sk_buff *veth_xdp_rcv_one(struct veth_rq *rq,
break;
case XDP_TX:
orig_frame = *frame;
- xdp.data_hard_start = head;
xdp.rxq->mem = frame->mem;
if (unlikely(veth_xdp_tx(rq, &xdp, bq) < 0)) {
trace_xdp_exception(rq->dev, xdp_prog, act);
@@ -605,7 +606,6 @@ static struct sk_buff *veth_xdp_rcv_one(struct veth_rq *rq,
goto xdp_xmit;
case XDP_REDIRECT:
orig_frame = *frame;
- xdp.data_hard_start = head;
xdp.rxq->mem = frame->mem;
if (xdp_do_redirect(rq->dev, &xdp, xdp_prog)) {
frame = &orig_frame;
@@ -629,7 +629,7 @@ static struct sk_buff *veth_xdp_rcv_one(struct veth_rq *rq,
rcu_read_unlock();
headroom = sizeof(struct xdp_frame) + frame->headroom - delta;
- skb = veth_build_skb(head, headroom, len, 0);
+ skb = veth_build_skb(hard_start, headroom, len, 0);
if (!skb) {
xdp_return_frame(frame);
stats->rx_drops++;