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authorSong Liu <songliubraving@fb.com>2018-10-19 09:57:57 -0700
committerAlexei Starovoitov <ast@kernel.org>2018-10-19 13:49:34 -0700
commitb39b5f411dcfce28ff954e5d6acb2c11be3cb0ec (patch)
tree4f724a3269469e76ed30c674bf52ddef3fb93db0
parent2929ad29a3015120ab64c86f362fc2a590ceb69c (diff)
bpf: add cg_skb_is_valid_access for BPF_PROG_TYPE_CGROUP_SKB
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>
-rw-r--r--include/linux/filter.h21
-rw-r--r--kernel/bpf/cgroup.c6
-rw-r--r--net/core/filter.c36
3 files changed, 62 insertions, 1 deletions
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 5771874bc01e..91b4c934f02e 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -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
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;
diff --git a/net/core/filter.c b/net/core/filter.c
index ea48ec789b5c..5fd5139e8638 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -5352,6 +5352,40 @@ static bool sk_filter_is_valid_access(int off, int size,
return bpf_skb_is_valid_access(off, size, type, prog, info);
}
+static bool cg_skb_is_valid_access(int off, int size,
+ enum bpf_access_type type,
+ const struct bpf_prog *prog,
+ struct bpf_insn_access_aux *info)
+{
+ switch (off) {
+ case bpf_ctx_range(struct __sk_buff, tc_classid):
+ case bpf_ctx_range(struct __sk_buff, data_meta):
+ case bpf_ctx_range(struct __sk_buff, flow_keys):
+ return false;
+ }
+ if (type == BPF_WRITE) {
+ switch (off) {
+ case bpf_ctx_range(struct __sk_buff, mark):
+ case bpf_ctx_range(struct __sk_buff, priority):
+ case bpf_ctx_range_till(struct __sk_buff, cb[0], cb[4]):
+ break;
+ default:
+ return false;
+ }
+ }
+
+ switch (off) {
+ case bpf_ctx_range(struct __sk_buff, data):
+ info->reg_type = PTR_TO_PACKET;
+ break;
+ case bpf_ctx_range(struct __sk_buff, data_end):
+ info->reg_type = PTR_TO_PACKET_END;
+ break;
+ }
+
+ return bpf_skb_is_valid_access(off, size, type, prog, info);
+}
+
static bool lwt_is_valid_access(int off, int size,
enum bpf_access_type type,
const struct bpf_prog *prog,
@@ -7044,7 +7078,7 @@ const struct bpf_prog_ops xdp_prog_ops = {
const struct bpf_verifier_ops cg_skb_verifier_ops = {
.get_func_proto = cg_skb_func_proto,
- .is_valid_access = sk_filter_is_valid_access,
+ .is_valid_access = cg_skb_is_valid_access,
.convert_ctx_access = bpf_convert_ctx_access,
};

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