Merge branch 'cg_skb_direct_pkt_access'

Song Liu says:

====================
Changes v7 -> v8:
1. Dynamically allocate the dummy sk to avoid race conditions.

Changes v6 -> v7:
1. Make dummy sk a global variable (test_run_sk).

Changes v5 -> v6:
1. Fixed dummy sk in bpf_prog_test_run_skb() as suggested by Eric Dumazet.

Changes v4 -> v5:
1. Replaced bpf_compute_and_save_data_pointers() with
   bpf_compute_and_save_data_end();
   Replaced bpf_restore_data_pointers() with bpf_restore_data_end().
2. Fixed indentation in test_verifier.c

Changes v3 -> v4:
1. Fixed crash issue reported by Alexei.

Changes v2 -> v3:
1. Added helper function bpf_compute_and_save_data_pointers() and
   bpf_restore_data_pointers().

Changes v1 -> v2:
1. Updated the list of read-only fields, and read-write fields.
2. Added dummy sk to bpf_prog_test_run_skb().

This set enables BPF program of type BPF_PROG_TYPE_CGROUP_SKB to access
some __skb_buff data directly.
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index 00f6ed2e4f9a..9425c2fb872f 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -553,6 +553,7 @@ int __cgroup_bpf_run_filter_skb(struct sock *sk,
 {
 	unsigned int offset = skb->data - skb_network_header(skb);
 	struct sock *save_sk;
+	void *saved_data_end;
 	struct cgroup *cgrp;
 	int ret;
 
@@ -566,8 +567,13 @@ int __cgroup_bpf_run_filter_skb(struct sock *sk,
 	save_sk = skb->sk;
 	skb->sk = sk;
 	__skb_push(skb, offset);
+
+	/* compute pointers for the bpf prog */
+	bpf_compute_and_save_data_end(skb, &saved_data_end);
+
 	ret = BPF_PROG_RUN_ARRAY(cgrp->bpf.effective[type], skb,
 				 bpf_prog_run_save_cb);
+	bpf_restore_data_end(skb, saved_data_end);
 	__skb_pull(skb, offset);
 	skb->sk = save_sk;
 	return ret == 1 ? 0 : -EPERM;