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031097d9e0
linux/net/ipv4/tcp_bpf.c
Jakub Kicinski 031097d9e0 net: skmsg: fix TLS 1.3 crash with full sk_msg 
TLS 1.3 started using the entry at the end of the SG array
for chaining-in the single byte content type entry. This mostly
works:

[ E E E E E E . . ]
  ^           ^
   start       end

                 E < content type
               /
[ E E E E E E C . ]
  ^           ^
   start       end

(Where E denotes a populated SG entry; C denotes a chaining entry.)

If the array is full, however, the end will point to the start:

[ E E E E E E E E ]
  ^
   start
   end

And we end up overwriting the start:

    E < content type
   /
[ C E E E E E E E ]
  ^
   start
   end

The sg array is supposed to be a circular buffer with start and
end markers pointing anywhere. In case where start > end
(i.e. the circular buffer has "wrapped") there is an extra entry
reserved at the end to chain the two halves together.

[ E E E E E E . . l ]

(Where l is the reserved entry for "looping" back to front.

As suggested by John, let's reserve another entry for chaining
SG entries after the main circular buffer. Note that this entry
has to be pointed to by the end entry so its position is not fixed.

Examples of full messages:

[ E E E E E E E E . l ]
  ^               ^
   start           end

   <---------------.
[ E E . E E E E E E l ]
      ^ ^
   end   start

Now the end will always point to an unused entry, so TLS 1.3
can always use it.

Fixes: 130b392c6c ("net: tls: Add tls 1.3 support")
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2019-11-28 22:40:29 -08:00

697 lines
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// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2017 - 2018 Covalent IO, Inc. http://covalent.io */
#include <linux/skmsg.h>
#include <linux/filter.h>
#include <linux/bpf.h>
#include <linux/init.h>
#include <linux/wait.h>
#include <net/inet_common.h>
#include <net/tls.h>
static bool tcp_bpf_stream_read(const struct sock *sk)
{
struct sk_psock *psock;
bool empty = true;
rcu_read_lock();
psock = sk_psock(sk);
if (likely(psock))
empty = list_empty(&psock->ingress_msg);
rcu_read_unlock();
return !empty;
}
static int tcp_bpf_wait_data(struct sock *sk, struct sk_psock *psock,
int flags, long timeo, int *err)
{
DEFINE_WAIT_FUNC(wait, woken_wake_function);
int ret = 0;
if (!timeo)
return ret;
add_wait_queue(sk_sleep(sk), &wait);
sk_set_bit(SOCKWQ_ASYNC_WAITDATA, sk);
ret = sk_wait_event(sk, &timeo,
!list_empty(&psock->ingress_msg) ||
!skb_queue_empty(&sk->sk_receive_queue), &wait);
sk_clear_bit(SOCKWQ_ASYNC_WAITDATA, sk);
remove_wait_queue(sk_sleep(sk), &wait);
return ret;
}
int __tcp_bpf_recvmsg(struct sock *sk, struct sk_psock *psock,
struct msghdr *msg, int len, int flags)
{
struct iov_iter *iter = &msg->msg_iter;
int peek = flags & MSG_PEEK;
int i, ret, copied = 0;
struct sk_msg *msg_rx;
msg_rx = list_first_entry_or_null(&psock->ingress_msg,
struct sk_msg, list);
while (copied != len) {
struct scatterlist *sge;
if (unlikely(!msg_rx))
break;
i = msg_rx->sg.start;
do {
struct page *page;
int copy;
sge = sk_msg_elem(msg_rx, i);
copy = sge->length;
page = sg_page(sge);
if (copied + copy > len)
copy = len - copied;
ret = copy_page_to_iter(page, sge->offset, copy, iter);
if (ret != copy) {
msg_rx->sg.start = i;
return -EFAULT;
}
copied += copy;
if (likely(!peek)) {
sge->offset += copy;
sge->length -= copy;
sk_mem_uncharge(sk, copy);
msg_rx->sg.size -= copy;
if (!sge->length) {
sk_msg_iter_var_next(i);
if (!msg_rx->skb)
put_page(page);
}
} else {
sk_msg_iter_var_next(i);
}
if (copied == len)
break;
} while (i != msg_rx->sg.end);
if (unlikely(peek)) {
msg_rx = list_next_entry(msg_rx, list);
continue;
}
msg_rx->sg.start = i;
if (!sge->length && msg_rx->sg.start == msg_rx->sg.end) {
list_del(&msg_rx->list);
if (msg_rx->skb)
consume_skb(msg_rx->skb);
kfree(msg_rx);
}
msg_rx = list_first_entry_or_null(&psock->ingress_msg,
struct sk_msg, list);
}
return copied;
}
EXPORT_SYMBOL_GPL(__tcp_bpf_recvmsg);
int tcp_bpf_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
int nonblock, int flags, int *addr_len)
{
struct sk_psock *psock;
int copied, ret;
if (unlikely(flags & MSG_ERRQUEUE))
return inet_recv_error(sk, msg, len, addr_len);
if (!skb_queue_empty(&sk->sk_receive_queue))
return tcp_recvmsg(sk, msg, len, nonblock, flags, addr_len);
psock = sk_psock_get(sk);
if (unlikely(!psock))
return tcp_recvmsg(sk, msg, len, nonblock, flags, addr_len);
lock_sock(sk);
msg_bytes_ready:
copied = __tcp_bpf_recvmsg(sk, psock, msg, len, flags);
if (!copied) {
int data, err = 0;
long timeo;
timeo = sock_rcvtimeo(sk, nonblock);
data = tcp_bpf_wait_data(sk, psock, flags, timeo, &err);
if (data) {
if (skb_queue_empty(&sk->sk_receive_queue))
goto msg_bytes_ready;
release_sock(sk);
sk_psock_put(sk, psock);
return tcp_recvmsg(sk, msg, len, nonblock, flags, addr_len);
}
if (err) {
ret = err;
goto out;
}
copied = -EAGAIN;
}
ret = copied;
out:
release_sock(sk);
sk_psock_put(sk, psock);
return ret;
}
static int bpf_tcp_ingress(struct sock *sk, struct sk_psock *psock,
struct sk_msg *msg, u32 apply_bytes, int flags)
{
bool apply = apply_bytes;
struct scatterlist *sge;
u32 size, copied = 0;
struct sk_msg *tmp;
int i, ret = 0;
tmp = kzalloc(sizeof(*tmp), __GFP_NOWARN | GFP_KERNEL);
if (unlikely(!tmp))
return -ENOMEM;
lock_sock(sk);
tmp->sg.start = msg->sg.start;
i = msg->sg.start;
do {
sge = sk_msg_elem(msg, i);
size = (apply && apply_bytes < sge->length) ?
apply_bytes : sge->length;
if (!sk_wmem_schedule(sk, size)) {
if (!copied)
ret = -ENOMEM;
break;
}
sk_mem_charge(sk, size);
sk_msg_xfer(tmp, msg, i, size);
copied += size;
if (sge->length)
get_page(sk_msg_page(tmp, i));
sk_msg_iter_var_next(i);
tmp->sg.end = i;
if (apply) {
apply_bytes -= size;
if (!apply_bytes)
break;
}
} while (i != msg->sg.end);
if (!ret) {
msg->sg.start = i;
msg->sg.size -= apply_bytes;
sk_psock_queue_msg(psock, tmp);
sk_psock_data_ready(sk, psock);
} else {
sk_msg_free(sk, tmp);
kfree(tmp);
}
release_sock(sk);
return ret;
}
static int tcp_bpf_push(struct sock *sk, struct sk_msg *msg, u32 apply_bytes,
int flags, bool uncharge)
{
bool apply = apply_bytes;
struct scatterlist *sge;
struct page *page;
int size, ret = 0;
u32 off;
while (1) {
bool has_tx_ulp;
sge = sk_msg_elem(msg, msg->sg.start);
size = (apply && apply_bytes < sge->length) ?
apply_bytes : sge->length;
off = sge->offset;
page = sg_page(sge);
tcp_rate_check_app_limited(sk);
retry:
has_tx_ulp = tls_sw_has_ctx_tx(sk);
if (has_tx_ulp) {
flags |= MSG_SENDPAGE_NOPOLICY;
ret = kernel_sendpage_locked(sk,
page, off, size, flags);
} else {
ret = do_tcp_sendpages(sk, page, off, size, flags);
}
if (ret <= 0)
return ret;
if (apply)
apply_bytes -= ret;
msg->sg.size -= ret;
sge->offset += ret;
sge->length -= ret;
if (uncharge)
sk_mem_uncharge(sk, ret);
if (ret != size) {
size -= ret;
off += ret;
goto retry;
}
if (!sge->length) {
put_page(page);
sk_msg_iter_next(msg, start);
sg_init_table(sge, 1);
if (msg->sg.start == msg->sg.end)
break;
}
if (apply && !apply_bytes)
break;
}
return 0;
}
static int tcp_bpf_push_locked(struct sock *sk, struct sk_msg *msg,
u32 apply_bytes, int flags, bool uncharge)
{
int ret;
lock_sock(sk);
ret = tcp_bpf_push(sk, msg, apply_bytes, flags, uncharge);
release_sock(sk);
return ret;
}
int tcp_bpf_sendmsg_redir(struct sock *sk, struct sk_msg *msg,
u32 bytes, int flags)
{
bool ingress = sk_msg_to_ingress(msg);
struct sk_psock *psock = sk_psock_get(sk);
int ret;
if (unlikely(!psock)) {
sk_msg_free(sk, msg);
return 0;
}
ret = ingress ? bpf_tcp_ingress(sk, psock, msg, bytes, flags) :
tcp_bpf_push_locked(sk, msg, bytes, flags, false);
sk_psock_put(sk, psock);
return ret;
}
EXPORT_SYMBOL_GPL(tcp_bpf_sendmsg_redir);
static int tcp_bpf_send_verdict(struct sock *sk, struct sk_psock *psock,
struct sk_msg *msg, int *copied, int flags)
{
bool cork = false, enospc = sk_msg_full(msg);
struct sock *sk_redir;
u32 tosend, delta = 0;
int ret;
more_data:
if (psock->eval == __SK_NONE) {
/* Track delta in msg size to add/subtract it on SK_DROP from
* returned to user copied size. This ensures user doesn't
* get a positive return code with msg_cut_data and SK_DROP
* verdict.
*/
delta = msg->sg.size;
psock->eval = sk_psock_msg_verdict(sk, psock, msg);
if (msg->sg.size < delta)
delta -= msg->sg.size;
else
delta = 0;
}
if (msg->cork_bytes &&
msg->cork_bytes > msg->sg.size && !enospc) {
psock->cork_bytes = msg->cork_bytes - msg->sg.size;
if (!psock->cork) {
psock->cork = kzalloc(sizeof(*psock->cork),
GFP_ATOMIC | __GFP_NOWARN);
if (!psock->cork)
return -ENOMEM;
}
memcpy(psock->cork, msg, sizeof(*msg));
return 0;
}
tosend = msg->sg.size;
if (psock->apply_bytes && psock->apply_bytes < tosend)
tosend = psock->apply_bytes;
switch (psock->eval) {
case __SK_PASS:
ret = tcp_bpf_push(sk, msg, tosend, flags, true);
if (unlikely(ret)) {
*copied -= sk_msg_free(sk, msg);
break;
}
sk_msg_apply_bytes(psock, tosend);
break;
case __SK_REDIRECT:
sk_redir = psock->sk_redir;
sk_msg_apply_bytes(psock, tosend);
if (psock->cork) {
cork = true;
psock->cork = NULL;
}
sk_msg_return(sk, msg, tosend);
release_sock(sk);
ret = tcp_bpf_sendmsg_redir(sk_redir, msg, tosend, flags);
lock_sock(sk);
if (unlikely(ret < 0)) {
int free = sk_msg_free_nocharge(sk, msg);
if (!cork)
*copied -= free;
}
if (cork) {
sk_msg_free(sk, msg);
kfree(msg);
msg = NULL;
ret = 0;
}
break;
case __SK_DROP:
default:
sk_msg_free_partial(sk, msg, tosend);
sk_msg_apply_bytes(psock, tosend);
*copied -= (tosend + delta);
return -EACCES;
}
if (likely(!ret)) {
if (!psock->apply_bytes) {
psock->eval = __SK_NONE;
if (psock->sk_redir) {
sock_put(psock->sk_redir);
psock->sk_redir = NULL;
}
}
if (msg &&
msg->sg.data[msg->sg.start].page_link &&
msg->sg.data[msg->sg.start].length)
goto more_data;
}
return ret;
}
static int tcp_bpf_sendmsg(struct sock *sk, struct msghdr *msg, size_t size)
{
struct sk_msg tmp, *msg_tx = NULL;
int copied = 0, err = 0;
struct sk_psock *psock;
long timeo;
int flags;
/* Don't let internal do_tcp_sendpages() flags through */
flags = (msg->msg_flags & ~MSG_SENDPAGE_DECRYPTED);
flags |= MSG_NO_SHARED_FRAGS;
psock = sk_psock_get(sk);
if (unlikely(!psock))
return tcp_sendmsg(sk, msg, size);
lock_sock(sk);
timeo = sock_sndtimeo(sk, msg->msg_flags & MSG_DONTWAIT);
while (msg_data_left(msg)) {
bool enospc = false;
u32 copy, osize;
if (sk->sk_err) {
err = -sk->sk_err;
goto out_err;
}
copy = msg_data_left(msg);
if (!sk_stream_memory_free(sk))
goto wait_for_sndbuf;
if (psock->cork) {
msg_tx = psock->cork;
} else {
msg_tx = &tmp;
sk_msg_init(msg_tx);
}
osize = msg_tx->sg.size;
err = sk_msg_alloc(sk, msg_tx, msg_tx->sg.size + copy, msg_tx->sg.end - 1);
if (err) {
if (err != -ENOSPC)
goto wait_for_memory;
enospc = true;
copy = msg_tx->sg.size - osize;
}
err = sk_msg_memcopy_from_iter(sk, &msg->msg_iter, msg_tx,
copy);
if (err < 0) {
sk_msg_trim(sk, msg_tx, osize);
goto out_err;
}
copied += copy;
if (psock->cork_bytes) {
if (size > psock->cork_bytes)
psock->cork_bytes = 0;
else
psock->cork_bytes -= size;
if (psock->cork_bytes && !enospc)
goto out_err;
/* All cork bytes are accounted, rerun the prog. */
psock->eval = __SK_NONE;
psock->cork_bytes = 0;
}
err = tcp_bpf_send_verdict(sk, psock, msg_tx, &copied, flags);
if (unlikely(err < 0))
goto out_err;
continue;
wait_for_sndbuf:
set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
wait_for_memory:
err = sk_stream_wait_memory(sk, &timeo);
if (err) {
if (msg_tx && msg_tx != psock->cork)
sk_msg_free(sk, msg_tx);
goto out_err;
}
}
out_err:
if (err < 0)
err = sk_stream_error(sk, msg->msg_flags, err);
release_sock(sk);
sk_psock_put(sk, psock);
return copied ? copied : err;
}
static int tcp_bpf_sendpage(struct sock *sk, struct page *page, int offset,
size_t size, int flags)
{
struct sk_msg tmp, *msg = NULL;
int err = 0, copied = 0;
struct sk_psock *psock;
bool enospc = false;
psock = sk_psock_get(sk);
if (unlikely(!psock))
return tcp_sendpage(sk, page, offset, size, flags);
lock_sock(sk);
if (psock->cork) {
msg = psock->cork;
} else {
msg = &tmp;
sk_msg_init(msg);
}
/* Catch case where ring is full and sendpage is stalled. */
if (unlikely(sk_msg_full(msg)))
goto out_err;
sk_msg_page_add(msg, page, size, offset);
sk_mem_charge(sk, size);
copied = size;
if (sk_msg_full(msg))
enospc = true;
if (psock->cork_bytes) {
if (size > psock->cork_bytes)
psock->cork_bytes = 0;
else
psock->cork_bytes -= size;
if (psock->cork_bytes && !enospc)
goto out_err;
/* All cork bytes are accounted, rerun the prog. */
psock->eval = __SK_NONE;
psock->cork_bytes = 0;
}
err = tcp_bpf_send_verdict(sk, psock, msg, &copied, flags);
out_err:
release_sock(sk);
sk_psock_put(sk, psock);
return copied ? copied : err;
}
static void tcp_bpf_remove(struct sock *sk, struct sk_psock *psock)
{
struct sk_psock_link *link;
while ((link = sk_psock_link_pop(psock))) {
sk_psock_unlink(sk, link);
sk_psock_free_link(link);
}
}
static void tcp_bpf_unhash(struct sock *sk)
{
void (*saved_unhash)(struct sock *sk);
struct sk_psock *psock;
rcu_read_lock();
psock = sk_psock(sk);
if (unlikely(!psock)) {
rcu_read_unlock();
if (sk->sk_prot->unhash)
sk->sk_prot->unhash(sk);
return;
}
saved_unhash = psock->saved_unhash;
tcp_bpf_remove(sk, psock);
rcu_read_unlock();
saved_unhash(sk);
}
static void tcp_bpf_close(struct sock *sk, long timeout)
{
void (*saved_close)(struct sock *sk, long timeout);
struct sk_psock *psock;
lock_sock(sk);
rcu_read_lock();
psock = sk_psock(sk);
if (unlikely(!psock)) {
rcu_read_unlock();
release_sock(sk);
return sk->sk_prot->close(sk, timeout);
}
saved_close = psock->saved_close;
tcp_bpf_remove(sk, psock);
rcu_read_unlock();
release_sock(sk);
saved_close(sk, timeout);
}
enum {
TCP_BPF_IPV4,
TCP_BPF_IPV6,
TCP_BPF_NUM_PROTS,
};
enum {
TCP_BPF_BASE,
TCP_BPF_TX,
TCP_BPF_NUM_CFGS,
};
static struct proto *tcpv6_prot_saved __read_mostly;
static DEFINE_SPINLOCK(tcpv6_prot_lock);
static struct proto tcp_bpf_prots[TCP_BPF_NUM_PROTS][TCP_BPF_NUM_CFGS];
static void tcp_bpf_rebuild_protos(struct proto prot[TCP_BPF_NUM_CFGS],
struct proto *base)
{
prot[TCP_BPF_BASE] = *base;
prot[TCP_BPF_BASE].unhash = tcp_bpf_unhash;
prot[TCP_BPF_BASE].close = tcp_bpf_close;
prot[TCP_BPF_BASE].recvmsg = tcp_bpf_recvmsg;
prot[TCP_BPF_BASE].stream_memory_read = tcp_bpf_stream_read;
prot[TCP_BPF_TX] = prot[TCP_BPF_BASE];
prot[TCP_BPF_TX].sendmsg = tcp_bpf_sendmsg;
prot[TCP_BPF_TX].sendpage = tcp_bpf_sendpage;
}
static void tcp_bpf_check_v6_needs_rebuild(struct sock *sk, struct proto *ops)
{
if (sk->sk_family == AF_INET6 &&
unlikely(ops != smp_load_acquire(&tcpv6_prot_saved))) {
spin_lock_bh(&tcpv6_prot_lock);
if (likely(ops != tcpv6_prot_saved)) {
tcp_bpf_rebuild_protos(tcp_bpf_prots[TCP_BPF_IPV6], ops);
smp_store_release(&tcpv6_prot_saved, ops);
}
spin_unlock_bh(&tcpv6_prot_lock);
}
}
static int __init tcp_bpf_v4_build_proto(void)
{
tcp_bpf_rebuild_protos(tcp_bpf_prots[TCP_BPF_IPV4], &tcp_prot);
return 0;
}
core_initcall(tcp_bpf_v4_build_proto);
static void tcp_bpf_update_sk_prot(struct sock *sk, struct sk_psock *psock)
{
int family = sk->sk_family == AF_INET6 ? TCP_BPF_IPV6 : TCP_BPF_IPV4;
int config = psock->progs.msg_parser ? TCP_BPF_TX : TCP_BPF_BASE;
sk_psock_update_proto(sk, psock, &tcp_bpf_prots[family][config]);
}
static void tcp_bpf_reinit_sk_prot(struct sock *sk, struct sk_psock *psock)
{
int family = sk->sk_family == AF_INET6 ? TCP_BPF_IPV6 : TCP_BPF_IPV4;
int config = psock->progs.msg_parser ? TCP_BPF_TX : TCP_BPF_BASE;
/* Reinit occurs when program types change e.g. TCP_BPF_TX is removed
* or added requiring sk_prot hook updates. We keep original saved
* hooks in this case.
*/
sk->sk_prot = &tcp_bpf_prots[family][config];
}
static int tcp_bpf_assert_proto_ops(struct proto *ops)
{
/* In order to avoid retpoline, we make assumptions when we call
* into ops if e.g. a psock is not present. Make sure they are
* indeed valid assumptions.
*/
return ops->recvmsg == tcp_recvmsg &&
ops->sendmsg == tcp_sendmsg &&
ops->sendpage == tcp_sendpage ? 0 : -ENOTSUPP;
}
void tcp_bpf_reinit(struct sock *sk)
{
struct sk_psock *psock;
sock_owned_by_me(sk);
rcu_read_lock();
psock = sk_psock(sk);
tcp_bpf_reinit_sk_prot(sk, psock);
rcu_read_unlock();
}
int tcp_bpf_init(struct sock *sk)
{
struct proto *ops = READ_ONCE(sk->sk_prot);
struct sk_psock *psock;
sock_owned_by_me(sk);
rcu_read_lock();
psock = sk_psock(sk);
if (unlikely(!psock || psock->sk_proto ||
tcp_bpf_assert_proto_ops(ops))) {
rcu_read_unlock();
return -EINVAL;
}
tcp_bpf_check_v6_needs_rebuild(sk, ops);
tcp_bpf_update_sk_prot(sk, psock);
rcu_read_unlock();
return 0;
}
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