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bpf/cpumap: make sure frame_size for build_skb is aligned if headroom isn't

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The frame_size passed to build_skb must be aligned, else it is
possible that the embedded struct skb_shared_info gets unaligned.

For correctness make sure that xdpf->headroom in included in the
alignment. No upstream drivers can hit this, as all XDP drivers provide
an aligned headroom.  This was discovered when playing with implementing
XDP support for mvneta, which have a 2 bytes DSA header, and this
Marvell ARM64 platform didn't like doing atomic operations on an
unaligned skb_shinfo(skb)->dataref addresses.

Fixes: 1c601d829a ("bpf: cpumap xdp_buff to skb conversion and allocation")
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Jesper Dangaard Brouer 2018-12-19 17:00:23 +01:00 committed by Daniel Borkmann
parent d70f4ece9d
commit 77ea5f4cbe
1 changed files with 1 additions and 1 deletions
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2
kernel/bpf/cpumap.c
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@ -183,7 +183,7 @@ static struct sk_buff *cpu_map_build_skb(struct bpf_cpu_map_entry *rcpu,
* is not at a fixed memory location, with mixed length
* packets, which is bad for cache-line hotness.
*/
frame_size = SKB_DATA_ALIGN(xdpf->len) + xdpf->headroom +
frame_size = SKB_DATA_ALIGN(xdpf->len + xdpf->headroom) +
SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
pkt_data_start = xdpf->data - xdpf->headroom;