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;
__u32 family;
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.
Signed-off-by: Martin KaFai Lau <ka...@fb.com>
---
include/linux/bpf.h | 12 ++++
include/uapi/linux/bpf.h | 12 +++-
kernel/bpf/verifier.c | 129 +++++++++++++++++++++++++++------------
net/core/filter.c | 43 +++++++++++++
4 files changed, 156 insertions(+), 40 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 0394f1f9213b..72022a0c442d 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -162,6 +162,7 @@ enum bpf_arg_type {
ARG_PTR_TO_CTX, /* pointer to context */
ARG_ANYTHING, /* any (initialized) argument is ok */
ARG_PTR_TO_SOCKET, /* pointer to bpf_sock */
+ ARG_PTR_TO_SOCK_COMMON, /* pointer to __sk_buff->sk */
};
/* type of values returned from helper functions */
@@ -224,6 +225,8 @@ 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
@@ -887,6 +890,9 @@ 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,
@@ -895,6 +901,12 @@ 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)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 60b99b730a41..b7a5312c4ccf 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -2328,6 +2328,14 @@ union bpf_attr {
* "**y**".
* Return
* 0
+ *
+ * struct bpf_sock *bpf_sk_fullsock(struct bpf_sock *sk)
+ * Description
+ * This helper tests if a bpf_sock is a fullsock such that
+ * all the fields in bpf_sock can be accessed.
+ * Return
+ * The same pointer if *sk* is a fullsock. Otherwise,
+ * NULL is returned.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -2422,7 +2430,8 @@ union bpf_attr {
FN(map_peek_elem), \
FN(msg_push_data), \
FN(msg_pop_data), \
- FN(rc_pointer_rel),
+ FN(rc_pointer_rel), \
+ FN(sk_fullsock),
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
* function eBPF program intends to call
@@ -2542,6 +2551,7 @@ struct __sk_buff {
__u64 tstamp;
__u32 wire_len;
__u32 gso_segs;
+ __bpf_md_ptr(struct bpf_sock *, sk);
};
struct bpf_tunnel_key {
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 8c1c21cd50b4..b4500f29dff1 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -330,10 +330,17 @@ static bool type_is_pkt_pointer(enum bpf_reg_type type)
type == PTR_TO_PACKET_META;
}
+static bool type_is_sk_pointer(enum bpf_reg_type type)
+{
+ return type == PTR_TO_SOCKET ||
+ type == PTR_TO_SOCK_COMMON;
+}
+
static bool reg_type_may_be_null(enum bpf_reg_type type)
{
return type == PTR_TO_MAP_VALUE_OR_NULL ||
- type == PTR_TO_SOCKET_OR_NULL;
+ type == PTR_TO_SOCKET_OR_NULL ||
+ type == PTR_TO_SOCK_COMMON_OR_NULL;
}
static bool type_is_refcounted(enum bpf_reg_type type)
@@ -370,6 +377,12 @@ static bool is_release_function(enum bpf_func_id func_id)
return func_id == BPF_FUNC_sk_release;
}
+static bool is_acquire_function(enum bpf_func_id func_id)
+{
+ return func_id == BPF_FUNC_sk_lookup_tcp ||
+ func_id == BPF_FUNC_sk_lookup_udp;
+}
+
/* string representation of 'enum bpf_reg_type' */
static const char * const reg_type_str[] = {
[NOT_INIT] = "?",
@@ -385,6 +398,8 @@ static const char * const reg_type_str[] = {
[PTR_TO_FLOW_KEYS] = "flow_keys",
[PTR_TO_SOCKET] = "sock",
[PTR_TO_SOCKET_OR_NULL] = "sock_or_null",
+ [PTR_TO_SOCK_COMMON] = "sock_common",
+ [PTR_TO_SOCK_COMMON_OR_NULL] = "sock_common_or_null",
};
static char slot_type_char[] = {
@@ -611,13 +626,10 @@ static int acquire_reference_state(struct
bpf_verifier_env *env, int insn_idx)
}
/* release function corresponding to acquire_reference_state(). Idempotent. */
-static int __release_reference_state(struct bpf_func_state *state, int ptr_id)
+static int release_reference_state(struct bpf_func_state *state, int ptr_id)
{
int i, last_idx;
- if (!ptr_id)
- return -EFAULT;
-
last_idx = state->acquired_refs - 1;
for (i = 0; i < state->acquired_refs; i++) {
if (state->refs[i].id == ptr_id) {
@@ -629,21 +641,7 @@ static int __release_reference_state(struct bpf_func_state
*state, int ptr_id)
return 0;
}
}
- return -EFAULT;
-}
-
-/* variation on the above for cases where we expect that there must be an
- * outstanding reference for the specified ptr_id.
- */
-static int release_reference_state(struct bpf_verifier_env *env, int ptr_id)
-{
- struct bpf_func_state *state = cur_func(env);
- int err;
-
- err = __release_reference_state(state, ptr_id);
- if (WARN_ON_ONCE(err != 0))
- verbose(env, "verifier internal error: can't release
reference\n");
- return err;
+ return -EINVAL;
}
static int transfer_reference_state(struct bpf_func_state *dst,
@@ -1201,6 +1199,8 @@ static bool is_spillable_regtype(enum bpf_reg_type type)
case CONST_PTR_TO_MAP:
case PTR_TO_SOCKET:
case PTR_TO_SOCKET_OR_NULL:
+ case PTR_TO_SOCK_COMMON:
+ case PTR_TO_SOCK_COMMON_OR_NULL:
return true;
default:
return false;
@@ -1623,6 +1623,7 @@ static int check_sock_access(struct bpf_verifier_env
*env, u32 regno, int off,
struct bpf_reg_state *regs = cur_regs(env);
struct bpf_reg_state *reg = ®s[regno];
struct bpf_insn_access_aux info;
+ bool valid;
if (reg->smin_value < 0) {
verbose(env, "R%d min value is negative, either use unsigned
index or do a if (index >=0) check.\n",
@@ -1630,13 +1631,24 @@ static int check_sock_access(struct bpf_verifier_env
*env, u32 regno, int off,
return -EACCES;
}
- if (!bpf_sock_is_valid_access(off, size, t, &info)) {
- verbose(env, "invalid bpf_sock access off=%d size=%d\n",
- off, size);
- return -EACCES;
+ switch (reg->type) {
+ case PTR_TO_SOCK_COMMON:
+ valid = bpf_sock_common_is_valid_access(off, size, t, &info);
+ break;
+ case PTR_TO_SOCKET:
+ valid = bpf_sock_is_valid_access(off, size, t, &info);
+ break;
+ default:
+ valid = false;
}
- return 0;
+ if (valid)
+ return 0;
+
+ verbose(env, "R%d invalid %s access off=%d size=%d\n",
+ regno, reg_type_str[reg->type], off, size);
+
+ return -EACCES;
}
static bool __is_pointer_value(bool allow_ptr_leaks,
@@ -1662,8 +1674,14 @@ static bool is_ctx_reg(struct bpf_verifier_env *env, int
regno)
{
const struct bpf_reg_state *reg = reg_state(env, regno);
- return reg->type == PTR_TO_CTX ||
- reg->type == PTR_TO_SOCKET;
+ return reg->type == PTR_TO_CTX;
+}
+
+static bool is_sk_reg(struct bpf_verifier_env *env, int regno)
+{
+ const struct bpf_reg_state *reg = reg_state(env, regno);
+
+ return type_is_sk_pointer(reg->type);
}
static bool is_pkt_reg(struct bpf_verifier_env *env, int regno)
@@ -1774,6 +1792,9 @@ static int check_ptr_alignment(struct bpf_verifier_env
*env,
case PTR_TO_SOCKET:
pointer_desc = "sock ";
break;
+ case PTR_TO_SOCK_COMMON:
+ pointer_desc = "sock_common ";
+ break;
default:
break;
}
@@ -1977,11 +1998,14 @@ static int check_mem_access(struct bpf_verifier_env
*env, int insn_idx, u32 regn
* PTR_TO_PACKET[_META,_END]. In the latter
* case, we know the offset is zero.
*/
- if (reg_type == SCALAR_VALUE)
+ if (reg_type == SCALAR_VALUE) {
mark_reg_unknown(env, regs, value_regno);
- else
+ } else {
mark_reg_known_zero(env, regs,
value_regno);
+ if (reg_type_may_be_null(reg_type))
+ regs[value_regno].id = ++env->id_gen;
+ }
regs[value_regno].type = reg_type;
}
@@ -2027,9 +2051,10 @@ static int check_mem_access(struct bpf_verifier_env
*env, int insn_idx, u32 regn
err = check_flow_keys_access(env, off, size);
if (!err && t == BPF_READ && value_regno >= 0)
mark_reg_unknown(env, regs, value_regno);
- } else if (reg->type == PTR_TO_SOCKET) {
+ } else if (type_is_sk_pointer(reg->type)) {
if (t == BPF_WRITE) {
- verbose(env, "cannot write into socket\n");
+ verbose(env, "R%d cannot write into %s\n",
+ regno, reg_type_str[reg->type]);
return -EACCES;
}
err = check_sock_access(env, regno, off, size, t);
@@ -2076,7 +2101,8 @@ static int check_xadd(struct bpf_verifier_env *env, int
insn_idx, struct bpf_ins
if (is_ctx_reg(env, insn->dst_reg) ||
is_pkt_reg(env, insn->dst_reg) ||
- is_flow_key_reg(env, insn->dst_reg)) {
+ is_flow_key_reg(env, insn->dst_reg) ||
+ is_sk_reg(env, insn->dst_reg)) {
verbose(env, "BPF_XADD stores into R%d %s is not allowed\n",
insn->dst_reg,
reg_type_str[reg_state(env, insn->dst_reg)->type]);
@@ -2258,6 +2284,11 @@ static int check_func_arg(struct bpf_verifier_env *env,
u32 regno,
err = check_ctx_reg(env, reg, regno);
if (err < 0)
return err;
+ } else if (arg_type == ARG_PTR_TO_SOCK_COMMON) {
+ expected_type = PTR_TO_SOCK_COMMON;
+ /* Any sk pointer can be ARG_PTR_TO_SOCK_COMMON */
+ if (!type_is_sk_pointer(type))
+ goto err_type;
} else if (arg_type == ARG_PTR_TO_SOCKET) {
expected_type = PTR_TO_SOCKET;
if (type != expected_type)
@@ -2661,7 +2692,7 @@ static int release_reference(struct bpf_verifier_env *env,
for (i = 0; i <= vstate->curframe; i++)
release_reg_references(env, vstate->frame[i], meta->ptr_id);
- return release_reference_state(env, meta->ptr_id);
+ return release_reference_state(cur_func(env), meta->ptr_id);
}
static int check_func_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
@@ -2926,8 +2957,11 @@ static int check_helper_call(struct bpf_verifier_env
*env, int func_id, int insn
}
} else if (is_release_function(func_id)) {
err = release_reference(env, &meta);
- if (err)
+ if (err) {
+ verbose(env, "func %s#%d reference has not been
acquired before\n",
+ func_id_name(func_id), func_id);
return err;
+ }
}
regs = cur_regs(env);
@@ -2974,12 +3008,19 @@ static int check_helper_call(struct bpf_verifier_env
*env, int func_id, int insn
regs[BPF_REG_0].id = ++env->id_gen;
}
} else if (fn->ret_type == RET_PTR_TO_SOCKET_OR_NULL) {
- int id = acquire_reference_state(env, insn_idx);
- if (id < 0)
- return id;
mark_reg_known_zero(env, regs, BPF_REG_0);
regs[BPF_REG_0].type = PTR_TO_SOCKET_OR_NULL;
- regs[BPF_REG_0].id = id;
+ if (is_acquire_function(func_id)) {
+ int id = acquire_reference_state(env, insn_idx);
+
+ if (id < 0)
+ return id;
+ /* For release_reference() */
+ regs[BPF_REG_0].id = id;
+ } else {
+ /* For mark_ptr_or_null_reg() */
+ regs[BPF_REG_0].id = ++env->id_gen;
+ }
} else {
verbose(env, "unknown return type %d of func %s#%d\n",
fn->ret_type, func_id_name(func_id), func_id);
@@ -3239,6 +3280,8 @@ static int adjust_ptr_min_max_vals(struct
bpf_verifier_env *env,
case PTR_TO_PACKET_END:
case PTR_TO_SOCKET:
case PTR_TO_SOCKET_OR_NULL:
+ case PTR_TO_SOCK_COMMON:
+ case PTR_TO_SOCK_COMMON_OR_NULL:
verbose(env, "R%d pointer arithmetic on %s prohibited\n",
dst, reg_type_str[ptr_reg->type]);
return -EACCES;
@@ -4472,7 +4515,10 @@ static void mark_ptr_or_null_reg(struct bpf_func_state
*state,
}
} else if (reg->type == PTR_TO_SOCKET_OR_NULL) {
reg->type = PTR_TO_SOCKET;
+ } else if (reg->type == PTR_TO_SOCK_COMMON_OR_NULL) {
+ reg->type = PTR_TO_SOCK_COMMON;
}
+
if (is_null || !reg_is_refcounted(reg)) {
/* We don't need id from this point onwards anymore,
* thus we should better reset it, so that state
@@ -4495,7 +4541,7 @@ static void mark_ptr_or_null_regs(struct
bpf_verifier_state *vstate, u32 regno,
int i, j;
if (reg_is_refcounted_or_null(®s[regno]) && is_null)
- __release_reference_state(state, id);
+ release_reference_state(state, id);
for (i = 0; i < MAX_BPF_REG; i++)
mark_ptr_or_null_reg(state, ®s[i], id, is_null);
@@ -5656,6 +5702,8 @@ static bool regsafe(struct bpf_reg_state *rold, struct
bpf_reg_state *rcur,
case PTR_TO_FLOW_KEYS:
case PTR_TO_SOCKET:
case PTR_TO_SOCKET_OR_NULL:
+ case PTR_TO_SOCK_COMMON:
+ case PTR_TO_SOCK_COMMON_OR_NULL:
/* Only valid matches are exact, which memcmp() above
* would have accepted
*/
@@ -5973,6 +6021,8 @@ static bool reg_type_mismatch_ok(enum bpf_reg_type type)
case PTR_TO_CTX:
case PTR_TO_SOCKET:
case PTR_TO_SOCKET_OR_NULL:
+ case PTR_TO_SOCK_COMMON:
+ case PTR_TO_SOCK_COMMON_OR_NULL:
return false;
default:
return true;
@@ -6944,6 +6994,7 @@ static int convert_ctx_accesses(struct bpf_verifier_env
*env)
convert_ctx_access = ops->convert_ctx_access;
break;
case PTR_TO_SOCKET:
+ case PTR_TO_SOCK_COMMON:
convert_ctx_access = bpf_sock_convert_ctx_access;
break;
default:
diff --git a/net/core/filter.c b/net/core/filter.c
index 8ce421796ac6..7f9ff0517b67 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -1793,6 +1793,18 @@ static const struct bpf_func_proto
bpf_skb_pull_data_proto = {
.arg2_type = ARG_ANYTHING,
};
+BPF_CALL_1(bpf_sk_fullsock, struct sock *, sk)
+{
+ return sk_fullsock(sk) ? (unsigned long)sk : (unsigned long)NULL;
+}
+
+static const struct bpf_func_proto bpf_sk_fullsock_proto = {
+ .func = bpf_sk_fullsock,
+ .gpl_only = false,
+ .ret_type = RET_PTR_TO_SOCKET_OR_NULL,
+ .arg1_type = ARG_PTR_TO_SOCK_COMMON,
+};
+
static inline int sk_skb_try_make_writable(struct sk_buff *skb,
unsigned int write_len)
{
@@ -5388,6 +5400,8 @@ cg_skb_func_proto(enum bpf_func_id func_id, const struct
bpf_prog *prog)
switch (func_id) {
case BPF_FUNC_get_local_storage:
return &bpf_get_local_storage_proto;
+ case BPF_FUNC_sk_fullsock:
+ return &bpf_sk_fullsock_proto;
default:
return sk_filter_func_proto(func_id, prog);
}
@@ -5459,6 +5473,8 @@ tc_cls_act_func_proto(enum bpf_func_id func_id, const
struct bpf_prog *prog)
return &bpf_get_socket_uid_proto;
case BPF_FUNC_fib_lookup:
return &bpf_skb_fib_lookup_proto;
+ case BPF_FUNC_sk_fullsock:
+ return &bpf_sk_fullsock_proto;
#ifdef CONFIG_XFRM
case BPF_FUNC_skb_get_xfrm_state:
return &bpf_skb_get_xfrm_state_proto;
@@ -5746,6 +5762,11 @@ static bool bpf_skb_is_valid_access(int off, int size,
enum bpf_access_type type
if (size != sizeof(__u64))
return false;
break;
+ case offsetof(struct __sk_buff, sk):
+ if (type == BPF_WRITE || size != sizeof(__u64))
+ return false;
+ info->reg_type = PTR_TO_SOCK_COMMON_OR_NULL;
+ break;
default:
/* Only narrow read access allowed for now. */
if (type == BPF_WRITE) {
@@ -5932,6 +5953,21 @@ static bool __sock_filter_check_size(int off, int size,
return size == size_default;
}
+bool bpf_sock_common_is_valid_access(int off, int size,
+ enum bpf_access_type type,
+ struct bpf_insn_access_aux *info)
+{
+ switch (off) {
+ case offsetof(struct bpf_sock, type):
+ case offsetof(struct bpf_sock, protocol):
+ case offsetof(struct bpf_sock, mark):
+ case offsetof(struct bpf_sock, priority):
+ return false;
+ default:
+ return bpf_sock_is_valid_access(off, size, type, info);
+ }
+}
+
bool bpf_sock_is_valid_access(int off, int size, enum bpf_access_type type,
struct bpf_insn_access_aux *info)
{
@@ -6730,6 +6766,13 @@ static u32 bpf_convert_ctx_access(enum bpf_access_type
type,
off += offsetof(struct qdisc_skb_cb, pkt_len);
*target_size = 4;
*insn++ = BPF_LDX_MEM(BPF_W, si->dst_reg, si->src_reg, off);
+ break;
+
+ case offsetof(struct __sk_buff, sk):
+ *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_buff, sk),
+ si->dst_reg, si->src_reg,
+ offsetof(struct sk_buff, sk));
+ break;
}
return insn - insn_buf;
--
2.17.1
