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author | Martin KaFai Lau <kafai@fb.com> | 2019-02-10 10:22:20 +0300 |
---|---|---|
committer | Alexei Starovoitov <ast@kernel.org> | 2019-02-11 06:46:17 +0300 |
commit | 46f8bc92758c6259bcf945e9216098661c1587cd (patch) | |
tree | 61e7dbd8136c73ed010b3bc53ae18eb50dc251db /include/linux/bpf.h | |
parent | 5f4566498dee5e38e36a015a968c22ed21568f0b (diff) | |
download | linux-46f8bc92758c6259bcf945e9216098661c1587cd.tar.xz |
bpf: Add a bpf_sock pointer to __sk_buff and a bpf_sk_fullsock helper
In kernel, it is common to check "skb->sk && sk_fullsock(skb->sk)"
before accessing the fields in sock. For example, in __netdev_pick_tx:
static u16 __netdev_pick_tx(struct net_device *dev, struct sk_buff *skb,
struct net_device *sb_dev)
{
/* ... */
struct sock *sk = skb->sk;
if (queue_index != new_index && sk &&
sk_fullsock(sk) &&
rcu_access_pointer(sk->sk_dst_cache))
sk_tx_queue_set(sk, new_index);
/* ... */
return queue_index;
}
This patch adds a "struct bpf_sock *sk" pointer to the "struct __sk_buff"
where a few of the convert_ctx_access() in filter.c has already been
accessing the skb->sk sock_common's fields,
e.g. sock_ops_convert_ctx_access().
"__sk_buff->sk" is a PTR_TO_SOCK_COMMON_OR_NULL in the verifier.
Some of the fileds in "bpf_sock" will not be directly
accessible through the "__sk_buff->sk" pointer. It is limited
by the new "bpf_sock_common_is_valid_access()".
e.g. The existing "type", "protocol", "mark" and "priority" in bpf_sock
are not allowed.
The newly added "struct bpf_sock *bpf_sk_fullsock(struct bpf_sock *sk)"
can be used to get a sk with all accessible fields in "bpf_sock".
This helper is added to both cg_skb and sched_(cls|act).
int cg_skb_foo(struct __sk_buff *skb) {
struct bpf_sock *sk;
sk = skb->sk;
if (!sk)
return 1;
sk = bpf_sk_fullsock(sk);
if (!sk)
return 1;
if (sk->family != AF_INET6 || sk->protocol != IPPROTO_TCP)
return 1;
/* some_traffic_shaping(); */
return 1;
}
(1) The sk is read only
(2) There is no new "struct bpf_sock_common" introduced.
(3) Future kernel sock's members could be added to bpf_sock only
instead of repeatedly adding at multiple places like currently
in bpf_sock_ops_md, bpf_sock_addr_md, sk_reuseport_md...etc.
(4) After "sk = skb->sk", the reg holding sk is in type
PTR_TO_SOCK_COMMON_OR_NULL.
(5) After bpf_sk_fullsock(), the return type will be in type
PTR_TO_SOCKET_OR_NULL which is the same as the return type of
bpf_sk_lookup_xxx().
However, bpf_sk_fullsock() does not take refcnt. The
acquire_reference_state() is only depending on the return type now.
To avoid it, a new is_acquire_function() is checked before calling
acquire_reference_state().
(6) The WARN_ON in "release_reference_state()" is no longer an
internal verifier bug.
When reg->id is not found in state->refs[], it means the
bpf_prog does something wrong like
"bpf_sk_release(bpf_sk_fullsock(skb->sk))" where reference has
never been acquired by calling "bpf_sk_fullsock(skb->sk)".
A -EINVAL and a verbose are done instead of WARN_ON. A test is
added to the test_verifier in a later patch.
Since the WARN_ON in "release_reference_state()" is no longer
needed, "__release_reference_state()" is folded into
"release_reference_state()" also.
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'include/linux/bpf.h')
-rw-r--r-- | include/linux/bpf.h | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/include/linux/bpf.h b/include/linux/bpf.h index bd169a7bcc93..a60463b45b54 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -194,6 +194,7 @@ enum bpf_arg_type { ARG_ANYTHING, /* any (initialized) argument is ok */ ARG_PTR_TO_SOCKET, /* pointer to bpf_sock */ ARG_PTR_TO_SPIN_LOCK, /* pointer to bpf_spin_lock */ + ARG_PTR_TO_SOCK_COMMON, /* pointer to sock_common */ }; /* type of values returned from helper functions */ @@ -256,6 +257,8 @@ enum bpf_reg_type { PTR_TO_FLOW_KEYS, /* reg points to bpf_flow_keys */ PTR_TO_SOCKET, /* reg points to struct bpf_sock */ PTR_TO_SOCKET_OR_NULL, /* reg points to struct bpf_sock or NULL */ + PTR_TO_SOCK_COMMON, /* reg points to sock_common */ + PTR_TO_SOCK_COMMON_OR_NULL, /* reg points to sock_common or NULL */ }; /* The information passed from prog-specific *_is_valid_access @@ -920,6 +923,9 @@ void bpf_user_rnd_init_once(void); u64 bpf_user_rnd_u32(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5); #if defined(CONFIG_NET) +bool bpf_sock_common_is_valid_access(int off, int size, + enum bpf_access_type type, + struct bpf_insn_access_aux *info); bool bpf_sock_is_valid_access(int off, int size, enum bpf_access_type type, struct bpf_insn_access_aux *info); u32 bpf_sock_convert_ctx_access(enum bpf_access_type type, @@ -928,6 +934,12 @@ u32 bpf_sock_convert_ctx_access(enum bpf_access_type type, struct bpf_prog *prog, u32 *target_size); #else +static inline bool bpf_sock_common_is_valid_access(int off, int size, + enum bpf_access_type type, + struct bpf_insn_access_aux *info) +{ + return false; +} static inline bool bpf_sock_is_valid_access(int off, int size, enum bpf_access_type type, struct bpf_insn_access_aux *info) |