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bpf: add cg_skb_is_valid_access for BPF_PROG_TYPE_CGROUP_SKB

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BPF programs of BPF_PROG_TYPE_CGROUP_SKB need to access headers in the
skb. This patch enables direct access of skb for these programs.

Two helper functions bpf_compute_and_save_data_end() and
bpf_restore_data_end() are introduced. There are used in
__cgroup_bpf_run_filter_skb(), to compute proper data_end for the
BPF program, and restore original data afterwards.

Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Song Liu
2018-10-19 09:57:57 -07:00
committed by Alexei Starovoitov
parent 2929ad29a3
commit b39b5f411d
3 changed files with 62 additions and 1 deletions
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21
include/linux/filter.h
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@@ -548,6 +548,27 @@ static inline void bpf_compute_data_pointers(struct sk_buff *skb)
cb->data_end = skb->data + skb_headlen(skb);
}
/* Similar to bpf_compute_data_pointers(), except that save orginal
* data in cb->data and cb->meta_data for restore.
*/
static inline void bpf_compute_and_save_data_end(
struct sk_buff *skb, void **saved_data_end)
{
struct bpf_skb_data_end *cb = (struct bpf_skb_data_end *)skb->cb;
*saved_data_end = cb->data_end;
cb->data_end = skb->data + skb_headlen(skb);
}
/* Restore data saved by bpf_compute_data_pointers(). */
static inline void bpf_restore_data_end(
struct sk_buff *skb, void *saved_data_end)
{
struct bpf_skb_data_end *cb = (struct bpf_skb_data_end *)skb->cb;
cb->data_end = saved_data_end;
}
static inline u8 *bpf_skb_cb(struct sk_buff *skb)
{
/* eBPF programs may read/write skb->cb[] area to transfer meta