diff options
| author | Jesper Dangaard Brouer <brouer@redhat.com> | 2020-05-14 12:49:43 +0200 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2020-05-14 21:21:54 -0700 |
| commit | 5c8572251fabc5bb49fd623c064e95a9daf6a3e3 (patch) | |
| tree | af0d8d251053e850131e18b69960540f1188be58 /drivers/net/veth.c | |
| parent | db612f749e2454c506f20155bba2871f0307d133 (diff) | |
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.c | 8 |
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++; |