diff options
author | Florian Westphal <fw@strlen.de> | 2020-04-02 14:44:51 +0300 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2020-04-02 16:59:21 +0300 |
commit | 0b4f33def7bbde1ce2fea05f116639270e7acdc7 (patch) | |
tree | 26698bcc349d424a94e47409e998f1b6091f1a65 /net/mptcp | |
parent | d16fa759253ff7a42b5257d0db9784caef2da9c0 (diff) | |
download | linux-0b4f33def7bbde1ce2fea05f116639270e7acdc7.tar.xz |
mptcp: fix tcp fallback crash
Christoph Paasch reports following crash:
general protection fault [..]
CPU: 0 PID: 2874 Comm: syz-executor072 Not tainted 5.6.0-rc5 #62
RIP: 0010:__pv_queued_spin_lock_slowpath kernel/locking/qspinlock.c:471
[..]
queued_spin_lock_slowpath arch/x86/include/asm/qspinlock.h:50 [inline]
do_raw_spin_lock include/linux/spinlock.h:181 [inline]
spin_lock_bh include/linux/spinlock.h:343 [inline]
__mptcp_flush_join_list+0x44/0xb0 net/mptcp/protocol.c:278
mptcp_shutdown+0xb3/0x230 net/mptcp/protocol.c:1882
[..]
Problem is that mptcp_shutdown() socket isn't an mptcp socket,
its a plain tcp_sk. Thus, trying to access mptcp_sk specific
members accesses garbage.
Root cause is that accept() returns a fallback (tcp) socket, not an mptcp
one. There is code in getpeername to detect this and override the sockets
stream_ops. But this will only run when accept() caller provided a
sockaddr struct. "accept(fd, NULL, 0)" will therefore result in
mptcp stream ops, but with sock->sk pointing at a tcp_sk.
Update the existing fallback handling to detect this as well.
Moreover, mptcp_shutdown did not have fallback handling, and
mptcp_poll did it too late so add that there as well.
Reported-by: Christoph Paasch <cpaasch@apple.com>
Tested-by: Christoph Paasch <cpaasch@apple.com>
Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/mptcp')
-rw-r--r-- | net/mptcp/protocol.c | 50 |
1 files changed, 46 insertions, 4 deletions
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 1833bc1f4a43..4cf88e3d5121 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -57,10 +57,43 @@ static bool __mptcp_needs_tcp_fallback(const struct mptcp_sock *msk) return msk->first && !sk_is_mptcp(msk->first); } +static struct socket *mptcp_is_tcpsk(struct sock *sk) +{ + struct socket *sock = sk->sk_socket; + + if (sock->sk != sk) + return NULL; + + if (unlikely(sk->sk_prot == &tcp_prot)) { + /* we are being invoked after mptcp_accept() has + * accepted a non-mp-capable flow: sk is a tcp_sk, + * not an mptcp one. + * + * Hand the socket over to tcp so all further socket ops + * bypass mptcp. + */ + sock->ops = &inet_stream_ops; + return sock; +#if IS_ENABLED(CONFIG_MPTCP_IPV6) + } else if (unlikely(sk->sk_prot == &tcpv6_prot)) { + sock->ops = &inet6_stream_ops; + return sock; +#endif + } + + return NULL; +} + static struct socket *__mptcp_tcp_fallback(struct mptcp_sock *msk) { + struct socket *sock; + sock_owned_by_me((const struct sock *)msk); + sock = mptcp_is_tcpsk((struct sock *)msk); + if (unlikely(sock)) + return sock; + if (likely(!__mptcp_needs_tcp_fallback(msk))) return NULL; @@ -84,6 +117,10 @@ static struct socket *__mptcp_socket_create(struct mptcp_sock *msk, int state) struct socket *ssock; int err; + ssock = __mptcp_tcp_fallback(msk); + if (unlikely(ssock)) + return ssock; + ssock = __mptcp_nmpc_socket(msk); if (ssock) goto set_state; @@ -1752,7 +1789,9 @@ static __poll_t mptcp_poll(struct file *file, struct socket *sock, msk = mptcp_sk(sk); lock_sock(sk); - ssock = __mptcp_nmpc_socket(msk); + ssock = __mptcp_tcp_fallback(msk); + if (!ssock) + ssock = __mptcp_nmpc_socket(msk); if (ssock) { mask = ssock->ops->poll(file, ssock, wait); release_sock(sk); @@ -1762,9 +1801,6 @@ static __poll_t mptcp_poll(struct file *file, struct socket *sock, release_sock(sk); sock_poll_wait(file, sock, wait); lock_sock(sk); - ssock = __mptcp_tcp_fallback(msk); - if (unlikely(ssock)) - return ssock->ops->poll(file, ssock, NULL); if (test_bit(MPTCP_DATA_READY, &msk->flags)) mask = EPOLLIN | EPOLLRDNORM; @@ -1783,11 +1819,17 @@ static int mptcp_shutdown(struct socket *sock, int how) { struct mptcp_sock *msk = mptcp_sk(sock->sk); struct mptcp_subflow_context *subflow; + struct socket *ssock; int ret = 0; pr_debug("sk=%p, how=%d", msk, how); lock_sock(sock->sk); + ssock = __mptcp_tcp_fallback(msk); + if (ssock) { + release_sock(sock->sk); + return inet_shutdown(ssock, how); + } if (how == SHUT_WR || how == SHUT_RDWR) inet_sk_state_store(sock->sk, TCP_FIN_WAIT1); |